libctf: support addition of types to dicts read via ctf_open()
libctf has long declared deserialized dictionaries (out of files or ELF
sections or memory buffers or whatever) to be read-only: back in the
furthest prehistory this was not the case, in that you could add a
few sorts of type to such dicts, but attempting to do so often caused
horrible memory corruption, so I banned the lot.
But it turns out real consumers want it (notably DTrace, which
synthesises pointers to types that don't have them and adds them to the
ctf_open()ed dicts if it needs them). Let's bring it back again, but
without the memory corruption and without the massive code duplication
required in days of yore to distinguish between static and dynamic
types: the representation of both types has been identical for a few
years, with the only difference being that types as a whole are stored in
a big buffer for types read in via ctf_open and per-type hashtables for
newly-added types.
So we discard the internally-visible concept of "readonly dictionaries"
in favour of declaring the *range of types* that were already present
when the dict was read in to be read-only: you can't modify them (say,
by adding members to them if they're structs, or calling ctf_set_array
on them), but you can add more types and point to them. (The API
remains the same, with calls sometimes returning ECTF_RDONLY, but now
they do so less often.)
This is a fairly invasive change, mostly because code written since the
ban was introduced didn't take the possibility of a static/dynamic split
into account. Some of these irregularities were hard to define as
anything but bugs.
Notably:
- The symbol handling was assuming that symbols only needed to be
looked for in dynamic hashtabs or static linker-laid-out indexed/
nonindexed layouts, but now we want to check both in case people
added more symbols to a dict they opened.
- The code that handles type additions wasn't checking to see if types
with the same name existed *at all* (so you could do
ctf_add_typedef (fp, "foo", bar) repeatedly without error). This
seems reasonable for types you just added, but we probably *do* want
to ban addition of types with names that override names we already
used in the ctf_open()ed portion, since that would probably corrupt
existing type relationships. (Doing things this way also avoids
causing new errors for any existing code that was doing this sort of
thing.)
- ctf_lookup_variable entirely failed to work for variables just added
by ctf_add_variable: you had to write the dict out and read it back
in again before they appeared.
- The symbol handling remembered what symbols you looked up but didn't
remember their types, so you could look up an object symbol and then
find it popping up when you asked for function symbols, which seems
less than ideal. Since we had to rejig things enough to be able to
distinguish function and object symbols internally anyway (in order
to give suitable errors if you try to add a symbol with a name that
already existed in the ctf_open()ed dict), this bug suddenly became
more visible and was easily fixed.
We do not (yet) support writing out dicts that have been previously read
in via ctf_open() or other deserializer (you can look things up in them,
but not write them out a second time). This never worked, so there is
no incompatibility; if it is needed at a later date, the serializer is a
little bit closer to having it work now (the only table we don't deal
with is the types table, and that's because the upcoming CTFv4 changes
are likely to make major changes to the way that table is represented
internally, so adding more code that depends on its current form seems
like a bad idea).
There is a new testcase that tests much of this, in particular that
modification of existing types is still banned and that you can add new
ones and chase them without error.
libctf/
* ctf-impl.h (struct ctf_dict.ctf_symhash): Split into...
(ctf_dict.ctf_symhash_func): ... this and...
(ctf_dict.ctf_symhash_objt): ... this.
(ctf_dict.ctf_stypes): New, counts static types.
(LCTF_INDEX_TO_TYPEPTR): Use it instead of CTF_RDWR.
(LCTF_RDWR): Deleted.
(LCTF_DIRTY): Renumbered.
(LCTF_LINKING): Likewise.
(ctf_lookup_variable_here): New.
(ctf_lookup_by_sym_or_name): Likewise.
(ctf_symbol_next_static): Likewise.
(ctf_add_variable_forced): Likewise.
(ctf_add_funcobjt_sym_forced): Likewise.
(ctf_simple_open_internal): Adjust.
(ctf_bufopen_internal): Likewise.
* ctf-create.c (ctf_grow_ptrtab): Adjust a lot to start with.
(ctf_create): Migrate a bunch of initializations into bufopen.
Force recreation of name tables. Do not forcibly override the
model, let ctf_bufopen do it.
(ctf_static_type): New.
(ctf_update): Drop LCTF_RDWR check.
(ctf_dynamic_type): Likewise.
(ctf_add_function): Likewise.
(ctf_add_type_internal): Likewise.
(ctf_rollback): Check ctf_stypes, not LCTF_RDWR.
(ctf_set_array): Likewise.
(ctf_add_struct_sized): Likewise.
(ctf_add_union_sized): Likewise.
(ctf_add_enum): Likewise.
(ctf_add_enumerator): Likewise (only on the target dict).
(ctf_add_member_offset): Likewise.
(ctf_add_generic): Drop LCTF_RDWR check. Ban addition of types
with colliding names.
(ctf_add_forward): Note safety under the new rules.
(ctf_add_variable): Split all but the existence check into...
(ctf_add_variable_forced): ... this new function.
(ctf_add_funcobjt_sym): Likewise...
(ctf_add_funcobjt_sym_forced): ... for this new function.
* ctf-link.c (ctf_link_add_linker_symbol): Ban calling on dicts
with any stypes.
(ctf_link_add_strtab): Likewise.
(ctf_link_shuffle_syms): Likewise.
(ctf_link_intern_extern_string): Note pre-existing prohibition.
* ctf-lookup.c (ctf_lookup_by_id): Drop LCTF_RDWR check.
(ctf_lookup_variable): Split out looking in a dict but not
its parent into...
(ctf_lookup_variable_here): ... this new function.
(ctf_lookup_symbol_idx): Track whether looking up a function or
object: cache them separately.
(ctf_symbol_next): Split out looking in non-dynamic symtypetab
entries to...
(ctf_symbol_next_static): ... this new function. Don't get confused
by the simultaneous presence of static and dynamic symtypetab entries.
(ctf_try_lookup_indexed): Don't waste time looking up symbols by
index before there can be any idea how symbols are numbered.
(ctf_lookup_by_sym_or_name): Distinguish between function and
data object lookups. Drop LCTF_RDWR.
(ctf_lookup_by_symbol): Adjust.
(ctf_lookup_by_symbol_name): Likewise.
* ctf-open.c (init_types): Rename to...
(init_static_types): ... this. Drop LCTF_RDWR. Populate ctf_stypes.
(ctf_simple_open): Drop writable arg.
(ctf_simple_open_internal): Likewise.
(ctf_bufopen): Likewise.
(ctf_bufopen_internal): Populate fields only used for writable dicts.
Drop LCTF_RDWR.
(ctf_dict_close): Cater for symhash cache split.
* ctf-serialize.c (ctf_serialize): Use ctf_stypes, not LCTF_RDWR.
* ctf-types.c (ctf_variable_next): Drop LCTF_RDWR.
* testsuite/libctf-lookup/add-to-opened*: New test.
libctf: archive, open: when opening, always set errp to something
ctf_arc_import_parent, called by the cached-opening machinery used by
ctf_archive_next and archive-wide lookup functions like
ctf_arc_lookup_symbol, has an err-pointer parameter like all other opening
functions. Unfortunately it unconditionally initializes it whenever
provided, even if there was no error, which can lead to its being
initialized to an uninitialized value. This is not technically an
API-contract violation, since we don't define what happens to the error
value except when an error happens, but it is still unpleasant.
Initialize it only when there is an actual error, so we never initialize it
to an uninitialized value.
While we're at it, improve all the opening pathways: on success, set errp to
0, rather than leaving it what it was, reducing the likelihood of
uninitialized error param returns in callers too. (This is inconsistent
with the treatment of ctf_errno(), but the err value being a parameter
passed in from outside makes the divergence acceptable: in open functions,
you're never going to be overwriting some old error value someone might want
to keep around across multiple calls, some of which are successful and some
of which are not.)
Soup up existing tests to verify all this.
Thanks to Bruce McCulloch for the original patch, and Stephen Brennan for
the report.
libctf/
PR libctf/32903
* ctf-archive.c (ctf_arc_open_internal): Zero errp on success.
(ctf_dict_open_sections): Zero errp at the start.
(ctf_arc_import_parent): Intialize err.
* ctf-open.c (ctf_bufopen): Zero errp at the start.
* testsuite/libctf-lookup/add-to-opened.c: Make sure one-element
archive opens update errp.
* testsuite/libctf-writable/ctf-compressed.c: Make sure real archive
opens update errp.
libctf: support addition of types to dicts read via ctf_open()
libctf has long declared deserialized dictionaries (out of files or ELF
sections or memory buffers or whatever) to be read-only: back in the
furthest prehistory this was not the case, in that you could add a
few sorts of type to such dicts, but attempting to do so often caused
horrible memory corruption, so I banned the lot.
But it turns out real consumers want it (notably DTrace, which
synthesises pointers to types that don't have them and adds them to the
ctf_open()ed dicts if it needs them). Let's bring it back again, but
without the memory corruption and without the massive code duplication
required in days of yore to distinguish between static and dynamic
types: the representation of both types has been identical for a few
years, with the only difference being that types as a whole are stored in
a big buffer for types read in via ctf_open and per-type hashtables for
newly-added types.
So we discard the internally-visible concept of "readonly dictionaries"
in favour of declaring the *range of types* that were already present
when the dict was read in to be read-only: you can't modify them (say,
by adding members to them if they're structs, or calling ctf_set_array
on them), but you can add more types and point to them. (The API
remains the same, with calls sometimes returning ECTF_RDONLY, but now
they do so less often.)
This is a fairly invasive change, mostly because code written since the
ban was introduced didn't take the possibility of a static/dynamic split
into account. Some of these irregularities were hard to define as
anything but bugs.
Notably:
- The symbol handling was assuming that symbols only needed to be
looked for in dynamic hashtabs or static linker-laid-out indexed/
nonindexed layouts, but now we want to check both in case people
added more symbols to a dict they opened.
- The code that handles type additions wasn't checking to see if types
with the same name existed *at all* (so you could do
ctf_add_typedef (fp, "foo", bar) repeatedly without error). This
seems reasonable for types you just added, but we probably *do* want
to ban addition of types with names that override names we already
used in the ctf_open()ed portion, since that would probably corrupt
existing type relationships. (Doing things this way also avoids
causing new errors for any existing code that was doing this sort of
thing.)
- ctf_lookup_variable entirely failed to work for variables just added
by ctf_add_variable: you had to write the dict out and read it back
in again before they appeared.
- The symbol handling remembered what symbols you looked up but didn't
remember their types, so you could look up an object symbol and then
find it popping up when you asked for function symbols, which seems
less than ideal. Since we had to rejig things enough to be able to
distinguish function and object symbols internally anyway (in order
to give suitable errors if you try to add a symbol with a name that
already existed in the ctf_open()ed dict), this bug suddenly became
more visible and was easily fixed.
We do not (yet) support writing out dicts that have been previously read
in via ctf_open() or other deserializer (you can look things up in them,
but not write them out a second time). This never worked, so there is
no incompatibility; if it is needed at a later date, the serializer is a
little bit closer to having it work now (the only table we don't deal
with is the types table, and that's because the upcoming CTFv4 changes
are likely to make major changes to the way that table is represented
internally, so adding more code that depends on its current form seems
like a bad idea).
There is a new testcase that tests much of this, in particular that
modification of existing types is still banned and that you can add new
ones and chase them without error.
libctf/
* ctf-impl.h (struct ctf_dict.ctf_symhash): Split into...
(ctf_dict.ctf_symhash_func): ... this and...
(ctf_dict.ctf_symhash_objt): ... this.
(ctf_dict.ctf_stypes): New, counts static types.
(LCTF_INDEX_TO_TYPEPTR): Use it instead of CTF_RDWR.
(LCTF_RDWR): Deleted.
(LCTF_DIRTY): Renumbered.
(LCTF_LINKING): Likewise.
(ctf_lookup_variable_here): New.
(ctf_lookup_by_sym_or_name): Likewise.
(ctf_symbol_next_static): Likewise.
(ctf_add_variable_forced): Likewise.
(ctf_add_funcobjt_sym_forced): Likewise.
(ctf_simple_open_internal): Adjust.
(ctf_bufopen_internal): Likewise.
* ctf-create.c (ctf_grow_ptrtab): Adjust a lot to start with.
(ctf_create): Migrate a bunch of initializations into bufopen.
Force recreation of name tables. Do not forcibly override the
model, let ctf_bufopen do it.
(ctf_static_type): New.
(ctf_update): Drop LCTF_RDWR check.
(ctf_dynamic_type): Likewise.
(ctf_add_function): Likewise.
(ctf_add_type_internal): Likewise.
(ctf_rollback): Check ctf_stypes, not LCTF_RDWR.
(ctf_set_array): Likewise.
(ctf_add_struct_sized): Likewise.
(ctf_add_union_sized): Likewise.
(ctf_add_enum): Likewise.
(ctf_add_enumerator): Likewise (only on the target dict).
(ctf_add_member_offset): Likewise.
(ctf_add_generic): Drop LCTF_RDWR check. Ban addition of types
with colliding names.
(ctf_add_forward): Note safety under the new rules.
(ctf_add_variable): Split all but the existence check into...
(ctf_add_variable_forced): ... this new function.
(ctf_add_funcobjt_sym): Likewise...
(ctf_add_funcobjt_sym_forced): ... for this new function.
* ctf-link.c (ctf_link_add_linker_symbol): Ban calling on dicts
with any stypes.
(ctf_link_add_strtab): Likewise.
(ctf_link_shuffle_syms): Likewise.
(ctf_link_intern_extern_string): Note pre-existing prohibition.
* ctf-lookup.c (ctf_lookup_by_id): Drop LCTF_RDWR check.
(ctf_lookup_variable): Split out looking in a dict but not
its parent into...
(ctf_lookup_variable_here): ... this new function.
(ctf_lookup_symbol_idx): Track whether looking up a function or
object: cache them separately.
(ctf_symbol_next): Split out looking in non-dynamic symtypetab
entries to...
(ctf_symbol_next_static): ... this new function. Don't get confused
by the simultaneous presence of static and dynamic symtypetab entries.
(ctf_try_lookup_indexed): Don't waste time looking up symbols by
index before there can be any idea how symbols are numbered.
(ctf_lookup_by_sym_or_name): Distinguish between function and
data object lookups. Drop LCTF_RDWR.
(ctf_lookup_by_symbol): Adjust.
(ctf_lookup_by_symbol_name): Likewise.
* ctf-open.c (init_types): Rename to...
(init_static_types): ... this. Drop LCTF_RDWR. Populate ctf_stypes.
(ctf_simple_open): Drop writable arg.
(ctf_simple_open_internal): Likewise.
(ctf_bufopen): Likewise.
(ctf_bufopen_internal): Populate fields only used for writable dicts.
Drop LCTF_RDWR.
(ctf_dict_close): Cater for symhash cache split.
* ctf-serialize.c (ctf_serialize): Use ctf_stypes, not LCTF_RDWR.
* ctf-types.c (ctf_variable_next): Drop LCTF_RDWR.
* testsuite/libctf-lookup/add-to-opened*: New test.
libctf: fix querying of large structures
After GCC PR 121411 is fixed, large structures (with offsets > 512MiB)
are written correctly... but libctf cannot query them properly unless
they are even bigger (> 4GiB), because it checks to see if the ctt_size
is CTF_LSIZE_SENT to decide whether to use a ctf_lmember_t or a
ctf_member_t to encode the structure members. But the structure member
offsets are in *bits*, not bytes: the right value to check is
CTF_LSTRUCT_THRESH, which is 1/8th the size.
(Thanks to Martin Pirker <martin.pirker1@chello.at> for the diagnosis
and fix.)
Testing this is a bit fun, because we don't want to emit an error if the
compiler is broken: but we cannot tell whether the compiler is broken
using the existing lookup harness, because its input is passed through
the linker (and thus the broken ld). So add another sort of link mode,
"objects", which keeps the constituent object files around and passes
both the final linker output and the object files that make it up to the
lookup program. Our testcase can then check the linker input to see if
the compiler is buggy, and only if it isn't check the linker output and
fail if things aren't right.
libctf/
PR libctf/33339
* ctf-types.c (ctf_struct_member): Check CTF_LSTRUCT_THRESH, not
CTF_LSIZE_SENT.
* testsuite/lib/ctf-lib.exp (run_lookup_test): New 'objects'
link option.
* testsuite/libctf-lookup/big-struct-corruption.*: New test.
* testsuite/libctf-lookup/big-struct-ctf.c: New test input.
libctf: fix querying of large structures
After GCC PR 121411 is fixed, large structures (with offsets > 512MiB)
are written correctly... but libctf cannot query them properly unless
they are even bigger (> 4GiB), because it checks to see if the ctt_size
is CTF_LSIZE_SENT to decide whether to use a ctf_lmember_t or a
ctf_member_t to encode the structure members. But the structure member
offsets are in *bits*, not bytes: the right value to check is
CTF_LSTRUCT_THRESH, which is 1/8th the size.
(Thanks to Martin Pirker <martin.pirker1@chello.at> for the diagnosis
and fix.)
Testing this is a bit fun, because we don't want to emit an error if the
compiler is broken: but we cannot tell whether the compiler is broken
using the existing lookup harness, because its input is passed through
the linker (and thus the broken ld). So add another sort of link mode,
"objects", which keeps the constituent object files around and passes
both the final linker output and the object files that make it up to the
lookup program. Our testcase can then check the linker input to see if
the compiler is buggy, and only if it isn't check the linker output and
fail if things aren't right.
libctf/
PR libctf/33339
* ctf-types.c (ctf_struct_member): Check CTF_LSTRUCT_THRESH, not
CTF_LSIZE_SENT.
* testsuite/lib/ctf-lib.exp (run_lookup_test): New 'objects'
link option.
* testsuite/libctf-lookup/big-struct-corruption.*: New test.
* testsuite/libctf-lookup/big-struct-ctf.c: New test input.
libctf: fix querying of large structures
After GCC PR 121411 is fixed, large structures (with offsets > 512MiB)
are written correctly... but libctf cannot query them properly unless
they are even bigger (> 4GiB), because it checks to see if the ctt_size
is CTF_LSIZE_SENT to decide whether to use a ctf_lmember_t or a
ctf_member_t to encode the structure members. But the structure member
offsets are in *bits*, not bytes: the right value to check is
CTF_LSTRUCT_THRESH, which is 1/8th the size.
(Thanks to Martin Pirker <martin.pirker1@chello.at> for the diagnosis
and fix.)
Testing this is a bit fun, because we don't want to emit an error if the
compiler is broken: but we cannot tell whether the compiler is broken
using the existing lookup harness, because its input is passed through
the linker (and thus the broken ld). So add another sort of link mode,
"objects", which keeps the constituent object files around and passes
both the final linker output and the object files that make it up to the
lookup program. Our testcase can then check the linker input to see if
the compiler is buggy, and only if it isn't check the linker output and
fail if things aren't right.
libctf/
PR libctf/33339
* ctf-types.c (ctf_struct_member): Check CTF_LSTRUCT_THRESH, not
CTF_LSIZE_SENT.
* testsuite/lib/ctf-lib.exp (run_lookup_test): New 'objects'
link option.
* testsuite/libctf-lookup/big-struct-corruption.*: New test.
* testsuite/libctf-lookup/big-struct-ctf.c: New test input.
libctf, include: find types of symbols by name
The existing ctf_lookup_by_symbol and ctf_arc_lookup_symbol functions
suffice to look up the types of symbols if the caller already has a
symbol number. But the caller often doesn't have one of those and only
knows the name of the symbol: also, in object files, the caller might
not have a useful symbol number in any sense (and neither does libctf:
the 'symbol number' we use in that case literally starts at 0 for the
lexicographically first-sorted symbol in the symtypetab and counts those
symbols, so it corresponds to nothing useful).
This means that even though object files have a symtypetab (generated by
the compiler or by ld -r), the only way we can look up anything in it is
to iterate over all symbols in turn with ctf_symbol_next until we find
the one we want.
This is unhelpful and pointlessly inefficient.
So add a pair of functions to look up symbols by name in a dict and in a
whole archive: ctf_lookup_by_symbol_name and ctf_arc_lookup_symbol_name.
These are identical to the existing functions except that they take
symbol names rather than symbol numbers.
To avoid insane repetition, we do some refactoring in the process, so
that both ctf_lookup_by_symbol and ctf_arc_lookup_symbol turn into thin
wrappers around internal functions that do both lookup by symbol index
and lookup by name. This massively reduces code duplication because
even the existing lookup-by-index stuff wants to use a name sometimes
(when looking up in indexed sections), and the new lookup-by-name stuff
has to turn it into an index sometimes (when looking up in non-indexed
sections): doing it this way lets us share most of that.
The actual name->index lookup is done by ctf_lookup_symbol_idx. We do
not anticipate this lookup to be as heavily used as ld.so symbol lookup
by many orders of magnitude, so using the ELF symbol hashes would
probably take more time to read them than is saved by using the hashes,
and it adds a lot of complexity. Instead, do a linear search for the
symbol name, caching all the name -> index mappings as we go, so that
future searches are likely to hit in the cache. To avoid having to
repeat this search over and over in a CTF archive when
ctf_arc_lookup_symbol_name is used, have cached archive lookups (the
sort done by ctf_arc_lookup_symbol* and the ctf_archive_next iterator)
pick out the first dict they cache in a given archive and store it in a
new ctf_archive field, ctfi_crossdict_cache. This can be used to store
cross-dictionary cached state that depends on things like the ELF symbol
table rather than the contents of any one dict. ctf_lookup_symbol_idx
then caches its name->index mappings in the dictionary named in the
crossdict cache, if any, so that ctf_lookup_symbol_idx in other dicts
in the same archive benefit from the previous linear search, and the
symtab only needs to be scanned at most once.
(Note that if you call ctf_lookup_by_symbol_name in one specific dict,
and then follow it with a ctf_arc_lookup_symbol_name, the former will
not use the crossdict cache because it's only populated by the dict
opens in ctf_arc_lookup_symbol_name. This is harmless except for a small
one-off waste of memory and time: it's only a cache, after all. We can
fix this later by using the archive caching machinery more
aggressively.)
In ctf-archive, we do similar things, turning ctf_arc_lookup_symbol into
a wrapper around a new function that does both index -> ID and name ->
ID lookups across all dicts in an archive. We add a new
ctfi_symnamedicts cache that maps symbol names to the ctf_dict_t * that
it was found in (so that linear searches for symbols don't need to be
repeated): but we also *remove* a cache, the ctfi_syms cache that was
memoizing the actual ctf_id_t returned from every call to
ctf_arc_lookup_symbol. This is pointless: all it saves is one call to
ctf_lookup_by_symbol, and that's basically an array lookup and nothing
more so isn't worth caching. (Equally, given that symbol -> index
mappings are cached by ctf_lookup_by_symbol_name, those calls are nearly
free after the first call, so there's no point caching the ctf_id_t in
that case either.)
We fix up one test that was doing manual symbol lookup to use
ctf_arc_lookup_symbol instead, and enhance it to check that the caching
layer is not totally broken: we also add a new test to do lookups in a
.o file, and another to do lookups in an archive with conflicted types
and make sure that sort of multi-dict lookup is actually working.
include/ChangeLog
2021-02-17 Nick Alcock <nick.alcock@oracle.com>
* ctf-api.h (ctf_arc_lookup_symbol_name): New.
(ctf_lookup_by_symbol_name): Likewise.
libctf/ChangeLog
2021-02-17 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (ctf_dict_t) <ctf_symhash>: New.
<ctf_symhash_latest>: Likewise.
(struct ctf_archive_internal) <ctfi_crossdict_cache>: New.
<ctfi_symnamedicts>: New.
<ctfi_syms>: Remove.
(ctf_lookup_symbol_name): Remove.
* ctf-lookup.c (ctf_lookup_symbol_name): Propagate errors from
parent properly. Make static.
(ctf_lookup_symbol_idx): New, linear search for the symbol name,
cached in the crossdict cache's ctf_symhash (if available), or
this dict's (otherwise).
(ctf_try_lookup_indexed): Allow the symname to be passed in.
(ctf_lookup_by_symbol): Turn into a wrapper around...
(ctf_lookup_by_sym_or_name): ... this, supporting name lookup too,
using ctf_lookup_symbol_idx in non-writable dicts. Special-case
name lookup in dynamic dicts without reported symbols, which have
no symtab or dynsymidx but where name lookup should still work.
(ctf_lookup_by_symbol_name): New, another wrapper.
* ctf-archive.c (enosym): Note that this is present in
ctfi_symnamedicts too.
(ctf_arc_close): Adjust for removal of ctfi_syms. Free the
ctfi_symnamedicts.
(ctf_arc_flush_caches): Likewise.
(ctf_dict_open_cached): Memoize the first cached dict in the
crossdict cache.
(ctf_arc_lookup_symbol): Turn into a wrapper around...
(ctf_arc_lookup_sym_or_name): ... this. No longer cache
ctf_id_t lookups: just call ctf_lookup_by_symbol as needed (but
still cache the dicts those lookups succeed in). Add
lookup-by-name support, with dicts of successful lookups cached in
ctfi_symnamedicts. Refactor the caching code a bit.
(ctf_arc_lookup_symbol_name): New, another wrapper.
* ctf-open.c (ctf_dict_close): Free the ctf_symhash.
* libctf.ver (LIBCTF_1.2): New version. Add
ctf_lookup_by_symbol_name, ctf_arc_lookup_symbol_name.
* testsuite/libctf-lookup/enum-symbol.c (main): Use
ctf_arc_lookup_symbol rather than looking up the name ourselves.
Fish it out repeatedly, to make sure that symbol caching isn't
broken.
(symidx_64): Remove.
(symidx_32): Remove.
* testsuite/libctf-lookup/enum-symbol-obj.lk: Test symbol lookup
in an unlinked object file (indexed symtypetab sections only).
* testsuite/libctf-writable/symtypetab-nonlinker-writeout.c
(try_maybe_reporting): Check symbol types via
ctf_lookup_by_symbol_name as well as ctf_symbol_next.
* testsuite/libctf-lookup/conflicting-type-syms.*: New test of
lookups in a multi-dict archive.
libctf, include: find types of symbols by name
The existing ctf_lookup_by_symbol and ctf_arc_lookup_symbol functions
suffice to look up the types of symbols if the caller already has a
symbol number. But the caller often doesn't have one of those and only
knows the name of the symbol: also, in object files, the caller might
not have a useful symbol number in any sense (and neither does libctf:
the 'symbol number' we use in that case literally starts at 0 for the
lexicographically first-sorted symbol in the symtypetab and counts those
symbols, so it corresponds to nothing useful).
This means that even though object files have a symtypetab (generated by
the compiler or by ld -r), the only way we can look up anything in it is
to iterate over all symbols in turn with ctf_symbol_next until we find
the one we want.
This is unhelpful and pointlessly inefficient.
So add a pair of functions to look up symbols by name in a dict and in a
whole archive: ctf_lookup_by_symbol_name and ctf_arc_lookup_symbol_name.
These are identical to the existing functions except that they take
symbol names rather than symbol numbers.
To avoid insane repetition, we do some refactoring in the process, so
that both ctf_lookup_by_symbol and ctf_arc_lookup_symbol turn into thin
wrappers around internal functions that do both lookup by symbol index
and lookup by name. This massively reduces code duplication because
even the existing lookup-by-index stuff wants to use a name sometimes
(when looking up in indexed sections), and the new lookup-by-name stuff
has to turn it into an index sometimes (when looking up in non-indexed
sections): doing it this way lets us share most of that.
The actual name->index lookup is done by ctf_lookup_symbol_idx. We do
not anticipate this lookup to be as heavily used as ld.so symbol lookup
by many orders of magnitude, so using the ELF symbol hashes would
probably take more time to read them than is saved by using the hashes,
and it adds a lot of complexity. Instead, do a linear search for the
symbol name, caching all the name -> index mappings as we go, so that
future searches are likely to hit in the cache. To avoid having to
repeat this search over and over in a CTF archive when
ctf_arc_lookup_symbol_name is used, have cached archive lookups (the
sort done by ctf_arc_lookup_symbol* and the ctf_archive_next iterator)
pick out the first dict they cache in a given archive and store it in a
new ctf_archive field, ctfi_crossdict_cache. This can be used to store
cross-dictionary cached state that depends on things like the ELF symbol
table rather than the contents of any one dict. ctf_lookup_symbol_idx
then caches its name->index mappings in the dictionary named in the
crossdict cache, if any, so that ctf_lookup_symbol_idx in other dicts
in the same archive benefit from the previous linear search, and the
symtab only needs to be scanned at most once.
(Note that if you call ctf_lookup_by_symbol_name in one specific dict,
and then follow it with a ctf_arc_lookup_symbol_name, the former will
not use the crossdict cache because it's only populated by the dict
opens in ctf_arc_lookup_symbol_name. This is harmless except for a small
one-off waste of memory and time: it's only a cache, after all. We can
fix this later by using the archive caching machinery more
aggressively.)
In ctf-archive, we do similar things, turning ctf_arc_lookup_symbol into
a wrapper around a new function that does both index -> ID and name ->
ID lookups across all dicts in an archive. We add a new
ctfi_symnamedicts cache that maps symbol names to the ctf_dict_t * that
it was found in (so that linear searches for symbols don't need to be
repeated): but we also *remove* a cache, the ctfi_syms cache that was
memoizing the actual ctf_id_t returned from every call to
ctf_arc_lookup_symbol. This is pointless: all it saves is one call to
ctf_lookup_by_symbol, and that's basically an array lookup and nothing
more so isn't worth caching. (Equally, given that symbol -> index
mappings are cached by ctf_lookup_by_symbol_name, those calls are nearly
free after the first call, so there's no point caching the ctf_id_t in
that case either.)
We fix up one test that was doing manual symbol lookup to use
ctf_arc_lookup_symbol instead, and enhance it to check that the caching
layer is not totally broken: we also add a new test to do lookups in a
.o file, and another to do lookups in an archive with conflicted types
and make sure that sort of multi-dict lookup is actually working.
include/ChangeLog
2021-02-17 Nick Alcock <nick.alcock@oracle.com>
* ctf-api.h (ctf_arc_lookup_symbol_name): New.
(ctf_lookup_by_symbol_name): Likewise.
libctf/ChangeLog
2021-02-17 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (ctf_dict_t) <ctf_symhash>: New.
<ctf_symhash_latest>: Likewise.
(struct ctf_archive_internal) <ctfi_crossdict_cache>: New.
<ctfi_symnamedicts>: New.
<ctfi_syms>: Remove.
(ctf_lookup_symbol_name): Remove.
* ctf-lookup.c (ctf_lookup_symbol_name): Propagate errors from
parent properly. Make static.
(ctf_lookup_symbol_idx): New, linear search for the symbol name,
cached in the crossdict cache's ctf_symhash (if available), or
this dict's (otherwise).
(ctf_try_lookup_indexed): Allow the symname to be passed in.
(ctf_lookup_by_symbol): Turn into a wrapper around...
(ctf_lookup_by_sym_or_name): ... this, supporting name lookup too,
using ctf_lookup_symbol_idx in non-writable dicts. Special-case
name lookup in dynamic dicts without reported symbols, which have
no symtab or dynsymidx but where name lookup should still work.
(ctf_lookup_by_symbol_name): New, another wrapper.
* ctf-archive.c (enosym): Note that this is present in
ctfi_symnamedicts too.
(ctf_arc_close): Adjust for removal of ctfi_syms. Free the
ctfi_symnamedicts.
(ctf_arc_flush_caches): Likewise.
(ctf_dict_open_cached): Memoize the first cached dict in the
crossdict cache.
(ctf_arc_lookup_symbol): Turn into a wrapper around...
(ctf_arc_lookup_sym_or_name): ... this. No longer cache
ctf_id_t lookups: just call ctf_lookup_by_symbol as needed (but
still cache the dicts those lookups succeed in). Add
lookup-by-name support, with dicts of successful lookups cached in
ctfi_symnamedicts. Refactor the caching code a bit.
(ctf_arc_lookup_symbol_name): New, another wrapper.
* ctf-open.c (ctf_dict_close): Free the ctf_symhash.
* libctf.ver (LIBCTF_1.2): New version. Add
ctf_lookup_by_symbol_name, ctf_arc_lookup_symbol_name.
* testsuite/libctf-lookup/enum-symbol.c (main): Use
ctf_arc_lookup_symbol rather than looking up the name ourselves.
Fish it out repeatedly, to make sure that symbol caching isn't
broken.
(symidx_64): Remove.
(symidx_32): Remove.
* testsuite/libctf-lookup/enum-symbol-obj.lk: Test symbol lookup
in an unlinked object file (indexed symtypetab sections only).
* testsuite/libctf-writable/symtypetab-nonlinker-writeout.c
(try_maybe_reporting): Check symbol types via
ctf_lookup_by_symbol_name as well as ctf_symbol_next.
* testsuite/libctf-lookup/conflicting-type-syms.*: New test of
lookups in a multi-dict archive.
libctf, include: find types of symbols by name
The existing ctf_lookup_by_symbol and ctf_arc_lookup_symbol functions
suffice to look up the types of symbols if the caller already has a
symbol number. But the caller often doesn't have one of those and only
knows the name of the symbol: also, in object files, the caller might
not have a useful symbol number in any sense (and neither does libctf:
the 'symbol number' we use in that case literally starts at 0 for the
lexicographically first-sorted symbol in the symtypetab and counts those
symbols, so it corresponds to nothing useful).
This means that even though object files have a symtypetab (generated by
the compiler or by ld -r), the only way we can look up anything in it is
to iterate over all symbols in turn with ctf_symbol_next until we find
the one we want.
This is unhelpful and pointlessly inefficient.
So add a pair of functions to look up symbols by name in a dict and in a
whole archive: ctf_lookup_by_symbol_name and ctf_arc_lookup_symbol_name.
These are identical to the existing functions except that they take
symbol names rather than symbol numbers.
To avoid insane repetition, we do some refactoring in the process, so
that both ctf_lookup_by_symbol and ctf_arc_lookup_symbol turn into thin
wrappers around internal functions that do both lookup by symbol index
and lookup by name. This massively reduces code duplication because
even the existing lookup-by-index stuff wants to use a name sometimes
(when looking up in indexed sections), and the new lookup-by-name stuff
has to turn it into an index sometimes (when looking up in non-indexed
sections): doing it this way lets us share most of that.
The actual name->index lookup is done by ctf_lookup_symbol_idx. We do
not anticipate this lookup to be as heavily used as ld.so symbol lookup
by many orders of magnitude, so using the ELF symbol hashes would
probably take more time to read them than is saved by using the hashes,
and it adds a lot of complexity. Instead, do a linear search for the
symbol name, caching all the name -> index mappings as we go, so that
future searches are likely to hit in the cache. To avoid having to
repeat this search over and over in a CTF archive when
ctf_arc_lookup_symbol_name is used, have cached archive lookups (the
sort done by ctf_arc_lookup_symbol* and the ctf_archive_next iterator)
pick out the first dict they cache in a given archive and store it in a
new ctf_archive field, ctfi_crossdict_cache. This can be used to store
cross-dictionary cached state that depends on things like the ELF symbol
table rather than the contents of any one dict. ctf_lookup_symbol_idx
then caches its name->index mappings in the dictionary named in the
crossdict cache, if any, so that ctf_lookup_symbol_idx in other dicts
in the same archive benefit from the previous linear search, and the
symtab only needs to be scanned at most once.
(Note that if you call ctf_lookup_by_symbol_name in one specific dict,
and then follow it with a ctf_arc_lookup_symbol_name, the former will
not use the crossdict cache because it's only populated by the dict
opens in ctf_arc_lookup_symbol_name. This is harmless except for a small
one-off waste of memory and time: it's only a cache, after all. We can
fix this later by using the archive caching machinery more
aggressively.)
In ctf-archive, we do similar things, turning ctf_arc_lookup_symbol into
a wrapper around a new function that does both index -> ID and name ->
ID lookups across all dicts in an archive. We add a new
ctfi_symnamedicts cache that maps symbol names to the ctf_dict_t * that
it was found in (so that linear searches for symbols don't need to be
repeated): but we also *remove* a cache, the ctfi_syms cache that was
memoizing the actual ctf_id_t returned from every call to
ctf_arc_lookup_symbol. This is pointless: all it saves is one call to
ctf_lookup_by_symbol, and that's basically an array lookup and nothing
more so isn't worth caching. (Equally, given that symbol -> index
mappings are cached by ctf_lookup_by_symbol_name, those calls are nearly
free after the first call, so there's no point caching the ctf_id_t in
that case either.)
We fix up one test that was doing manual symbol lookup to use
ctf_arc_lookup_symbol instead, and enhance it to check that the caching
layer is not totally broken: we also add a new test to do lookups in a
.o file, and another to do lookups in an archive with conflicted types
and make sure that sort of multi-dict lookup is actually working.
include/ChangeLog
2021-02-17 Nick Alcock <nick.alcock@oracle.com>
* ctf-api.h (ctf_arc_lookup_symbol_name): New.
(ctf_lookup_by_symbol_name): Likewise.
libctf/ChangeLog
2021-02-17 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (ctf_dict_t) <ctf_symhash>: New.
<ctf_symhash_latest>: Likewise.
(struct ctf_archive_internal) <ctfi_crossdict_cache>: New.
<ctfi_symnamedicts>: New.
<ctfi_syms>: Remove.
(ctf_lookup_symbol_name): Remove.
* ctf-lookup.c (ctf_lookup_symbol_name): Propagate errors from
parent properly. Make static.
(ctf_lookup_symbol_idx): New, linear search for the symbol name,
cached in the crossdict cache's ctf_symhash (if available), or
this dict's (otherwise).
(ctf_try_lookup_indexed): Allow the symname to be passed in.
(ctf_lookup_by_symbol): Turn into a wrapper around...
(ctf_lookup_by_sym_or_name): ... this, supporting name lookup too,
using ctf_lookup_symbol_idx in non-writable dicts. Special-case
name lookup in dynamic dicts without reported symbols, which have
no symtab or dynsymidx but where name lookup should still work.
(ctf_lookup_by_symbol_name): New, another wrapper.
* ctf-archive.c (enosym): Note that this is present in
ctfi_symnamedicts too.
(ctf_arc_close): Adjust for removal of ctfi_syms. Free the
ctfi_symnamedicts.
(ctf_arc_flush_caches): Likewise.
(ctf_dict_open_cached): Memoize the first cached dict in the
crossdict cache.
(ctf_arc_lookup_symbol): Turn into a wrapper around...
(ctf_arc_lookup_sym_or_name): ... this. No longer cache
ctf_id_t lookups: just call ctf_lookup_by_symbol as needed (but
still cache the dicts those lookups succeed in). Add
lookup-by-name support, with dicts of successful lookups cached in
ctfi_symnamedicts. Refactor the caching code a bit.
(ctf_arc_lookup_symbol_name): New, another wrapper.
* ctf-open.c (ctf_dict_close): Free the ctf_symhash.
* libctf.ver (LIBCTF_1.2): New version. Add
ctf_lookup_by_symbol_name, ctf_arc_lookup_symbol_name.
* testsuite/libctf-lookup/enum-symbol.c (main): Use
ctf_arc_lookup_symbol rather than looking up the name ourselves.
Fish it out repeatedly, to make sure that symbol caching isn't
broken.
(symidx_64): Remove.
(symidx_32): Remove.
* testsuite/libctf-lookup/enum-symbol-obj.lk: Test symbol lookup
in an unlinked object file (indexed symtypetab sections only).
* testsuite/libctf-writable/symtypetab-nonlinker-writeout.c
(try_maybe_reporting): Check symbol types via
ctf_lookup_by_symbol_name as well as ctf_symbol_next.
* testsuite/libctf-lookup/conflicting-type-syms.*: New test of
lookups in a multi-dict archive.
libctf, include: new functions for looking up enumerators
Three new functions for looking up the enum type containing a given
enumeration constant, and optionally that constant's value.
The simplest, ctf_lookup_enumerator, looks up a root-visible enumerator by
name in one dict: if the dict contains multiple such constants (which is
possible for dicts created by older versions of the libctf deduplicator),
ECTF_DUPLICATE is returned.
The next simplest, ctf_lookup_enumerator_next, is an iterator which returns
all enumerators with a given name in a given dict, whether root-visible or
not.
The most elaborate, ctf_arc_lookup_enumerator_next, finds all
enumerators with a given name across all dicts in an entire CTF archive,
whether root-visible or not, starting looking in the shared parent dict;
opened dicts are cached (as with all other ctf_arc_*lookup functions) so
that repeated use does not incur repeated opening costs.
All three of these return enumerator values as int64_t: unfortunately, API
compatibility concerns prevent us from doing the same with the other older
enum-related functions, which all return enumerator constant values as ints.
We may be forced to add symbol-versioning compatibility aliases that fix the
other functions in due course, bumping the soname for platforms that do not
support such things.
ctf_arc_lookup_enumerator_next is implemented as a nested ctf_archive_next
iterator, and inside that, a nested ctf_lookup_enumerator_next iterator
within each dict. To aid in this, add support to ctf_next_t iterators for
iterators that are implemented in terms of two simultaneous nested iterators
at once. (It has always been possible for callers to use as many nested or
semi-overlapping ctf_next_t iterators as they need, which is one of the
advantages of this style over the _iter style that calls a function for each
thing iterated over: the iterator change here permits *ctf_next_t iterators
themselves* to be implemented by iterating using multiple other iterators as
part of their internal operation, transparently to the caller.)
Also add a testcase that tests all these functions (which is fairly easy
because ctf_arc_lookup_enumerator_next is implemented in terms of
ctf_lookup_enumerator_next) in addition to enumeration addition in
ctf_open()ed dicts, ctf_add_enumerator duplicate enumerator addition, and
conflicting enumerator constant deduplication.
include/
* ctf-api.h (ctf_lookup_enumerator): New.
(ctf_lookup_enumerator_next): Likewise.
(ctf_arc_lookup_enumerator_next): Likewise.
libctf/
* libctf.ver: Add them.
* ctf-impl.h (ctf_next_t) <ctn_next_inner>: New.
* ctf-util.c (ctf_next_copy): Copy it.
(ctf_next_destroy): Destroy it.
* ctf-lookup.c (ctf_lookup_enumerator): New.
(ctf_lookup_enumerator_next): New.
* ctf-archive.c (ctf_arc_lookup_enumerator_next): New.
* testsuite/libctf-lookup/enumerator-iteration.*: New test.
* testsuite/libctf-lookup/enum-ctf-2.c: New test CTF, used by the
above.
libctf, include: find types of symbols by name
The existing ctf_lookup_by_symbol and ctf_arc_lookup_symbol functions
suffice to look up the types of symbols if the caller already has a
symbol number. But the caller often doesn't have one of those and only
knows the name of the symbol: also, in object files, the caller might
not have a useful symbol number in any sense (and neither does libctf:
the 'symbol number' we use in that case literally starts at 0 for the
lexicographically first-sorted symbol in the symtypetab and counts those
symbols, so it corresponds to nothing useful).
This means that even though object files have a symtypetab (generated by
the compiler or by ld -r), the only way we can look up anything in it is
to iterate over all symbols in turn with ctf_symbol_next until we find
the one we want.
This is unhelpful and pointlessly inefficient.
So add a pair of functions to look up symbols by name in a dict and in a
whole archive: ctf_lookup_by_symbol_name and ctf_arc_lookup_symbol_name.
These are identical to the existing functions except that they take
symbol names rather than symbol numbers.
To avoid insane repetition, we do some refactoring in the process, so
that both ctf_lookup_by_symbol and ctf_arc_lookup_symbol turn into thin
wrappers around internal functions that do both lookup by symbol index
and lookup by name. This massively reduces code duplication because
even the existing lookup-by-index stuff wants to use a name sometimes
(when looking up in indexed sections), and the new lookup-by-name stuff
has to turn it into an index sometimes (when looking up in non-indexed
sections): doing it this way lets us share most of that.
The actual name->index lookup is done by ctf_lookup_symbol_idx. We do
not anticipate this lookup to be as heavily used as ld.so symbol lookup
by many orders of magnitude, so using the ELF symbol hashes would
probably take more time to read them than is saved by using the hashes,
and it adds a lot of complexity. Instead, do a linear search for the
symbol name, caching all the name -> index mappings as we go, so that
future searches are likely to hit in the cache. To avoid having to
repeat this search over and over in a CTF archive when
ctf_arc_lookup_symbol_name is used, have cached archive lookups (the
sort done by ctf_arc_lookup_symbol* and the ctf_archive_next iterator)
pick out the first dict they cache in a given archive and store it in a
new ctf_archive field, ctfi_crossdict_cache. This can be used to store
cross-dictionary cached state that depends on things like the ELF symbol
table rather than the contents of any one dict. ctf_lookup_symbol_idx
then caches its name->index mappings in the dictionary named in the
crossdict cache, if any, so that ctf_lookup_symbol_idx in other dicts
in the same archive benefit from the previous linear search, and the
symtab only needs to be scanned at most once.
(Note that if you call ctf_lookup_by_symbol_name in one specific dict,
and then follow it with a ctf_arc_lookup_symbol_name, the former will
not use the crossdict cache because it's only populated by the dict
opens in ctf_arc_lookup_symbol_name. This is harmless except for a small
one-off waste of memory and time: it's only a cache, after all. We can
fix this later by using the archive caching machinery more
aggressively.)
In ctf-archive, we do similar things, turning ctf_arc_lookup_symbol into
a wrapper around a new function that does both index -> ID and name ->
ID lookups across all dicts in an archive. We add a new
ctfi_symnamedicts cache that maps symbol names to the ctf_dict_t * that
it was found in (so that linear searches for symbols don't need to be
repeated): but we also *remove* a cache, the ctfi_syms cache that was
memoizing the actual ctf_id_t returned from every call to
ctf_arc_lookup_symbol. This is pointless: all it saves is one call to
ctf_lookup_by_symbol, and that's basically an array lookup and nothing
more so isn't worth caching. (Equally, given that symbol -> index
mappings are cached by ctf_lookup_by_symbol_name, those calls are nearly
free after the first call, so there's no point caching the ctf_id_t in
that case either.)
We fix up one test that was doing manual symbol lookup to use
ctf_arc_lookup_symbol instead, and enhance it to check that the caching
layer is not totally broken: we also add a new test to do lookups in a
.o file, and another to do lookups in an archive with conflicted types
and make sure that sort of multi-dict lookup is actually working.
include/ChangeLog
2021-02-17 Nick Alcock <nick.alcock@oracle.com>
* ctf-api.h (ctf_arc_lookup_symbol_name): New.
(ctf_lookup_by_symbol_name): Likewise.
libctf/ChangeLog
2021-02-17 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (ctf_dict_t) <ctf_symhash>: New.
<ctf_symhash_latest>: Likewise.
(struct ctf_archive_internal) <ctfi_crossdict_cache>: New.
<ctfi_symnamedicts>: New.
<ctfi_syms>: Remove.
(ctf_lookup_symbol_name): Remove.
* ctf-lookup.c (ctf_lookup_symbol_name): Propagate errors from
parent properly. Make static.
(ctf_lookup_symbol_idx): New, linear search for the symbol name,
cached in the crossdict cache's ctf_symhash (if available), or
this dict's (otherwise).
(ctf_try_lookup_indexed): Allow the symname to be passed in.
(ctf_lookup_by_symbol): Turn into a wrapper around...
(ctf_lookup_by_sym_or_name): ... this, supporting name lookup too,
using ctf_lookup_symbol_idx in non-writable dicts. Special-case
name lookup in dynamic dicts without reported symbols, which have
no symtab or dynsymidx but where name lookup should still work.
(ctf_lookup_by_symbol_name): New, another wrapper.
* ctf-archive.c (enosym): Note that this is present in
ctfi_symnamedicts too.
(ctf_arc_close): Adjust for removal of ctfi_syms. Free the
ctfi_symnamedicts.
(ctf_arc_flush_caches): Likewise.
(ctf_dict_open_cached): Memoize the first cached dict in the
crossdict cache.
(ctf_arc_lookup_symbol): Turn into a wrapper around...
(ctf_arc_lookup_sym_or_name): ... this. No longer cache
ctf_id_t lookups: just call ctf_lookup_by_symbol as needed (but
still cache the dicts those lookups succeed in). Add
lookup-by-name support, with dicts of successful lookups cached in
ctfi_symnamedicts. Refactor the caching code a bit.
(ctf_arc_lookup_symbol_name): New, another wrapper.
* ctf-open.c (ctf_dict_close): Free the ctf_symhash.
* libctf.ver (LIBCTF_1.2): New version. Add
ctf_lookup_by_symbol_name, ctf_arc_lookup_symbol_name.
* testsuite/libctf-lookup/enum-symbol.c (main): Use
ctf_arc_lookup_symbol rather than looking up the name ourselves.
Fish it out repeatedly, to make sure that symbol caching isn't
broken.
(symidx_64): Remove.
(symidx_32): Remove.
* testsuite/libctf-lookup/enum-symbol-obj.lk: Test symbol lookup
in an unlinked object file (indexed symtypetab sections only).
* testsuite/libctf-writable/symtypetab-nonlinker-writeout.c
(try_maybe_reporting): Check symbol types via
ctf_lookup_by_symbol_name as well as ctf_symbol_next.
* testsuite/libctf-lookup/conflicting-type-syms.*: New test of
lookups in a multi-dict archive.
libctf, include: add ctf_dict_set_flag: less enum dup checking by default
The recent change to detect duplicate enum values and return ECTF_DUPLICATE
when found turns out to perturb a great many callers. In particular, the
pahole-created kernel BTF has the same problem we historically did, and
gleefully emits duplicated enum constants in profusion. Handling the
resulting duplicate errors from BTF -> CTF converters reasonably is
unreasonably difficult (it amounts to forcing them to skip some types or
reimplement the deduplicator).
So let's step back a bit. What we care about mostly is that the
deduplicator treat enums with conflicting enumeration constants as
conflicting types: programs that want to look up enumeration constant ->
value mappings using the new APIs to do so might well want the same checks
to apply to any ctf_add_* operations they carry out (and since they're
*using* the new APIs, added at the same time as this restriction was
imposed, there is likely to be no negative consequence of this).
So we want some way to allow processes that know about duplicate detection
to opt into it, while allowing everyone else to stay clear of it: but we
want ctf_link to get this behaviour even if its caller has opted out.
So add a new concept to the API: dict-wide CTF flags, set via
ctf_dict_set_flag, obtained via ctf_dict_get_flag. They are not bitflags
but simple arbitrary integers and an on/off value, stored in an unspecified
manner (the one current flag, we translate into an LCTF_* flag value in the
internal ctf_dict ctf_flags word). If you pass in an invalid flag or value
you get a new ECTF_BADFLAG error, so the caller can easily tell whether
flags added in future are valid with a particular libctf or not.
We check this flag in ctf_add_enumerator, and set it around the link
(including on child per-CU dicts). The newish enumerator-iteration test is
souped up to check the semantics of the flag as well.
The fact that the flag can be set and unset at any time has curious
consequences. You can unset the flag, insert a pile of duplicates, then set
it and expect the new duplicates to be detected, not only by
ctf_add_enumerator but also by ctf_lookup_enumerator. This means we now
have to maintain the ctf_names and conflicting_enums enum-duplication
tracking as new enums are added, not purely as the dict is opened.
Move that code out of init_static_types_internal and into a new
ctf_track_enumerator function that addition can also call.
(None of this affects the file format or serialization machinery, which has
to be able to handle duplicate enumeration constants no matter what.)
include/
* ctf-api.h (CTF_ERRORS) [ECTF_BADFLAG]: New.
(ECTF_NERR): Update.
(CTF_STRICT_NO_DUP_ENUMERATORS): New flag.
(ctf_dict_set_flag): New function.
(ctf_dict_get_flag): Likewise.
libctf/
* ctf-impl.h (LCTF_STRICT_NO_DUP_ENUMERATORS): New flag.
(ctf_track_enumerator): Declare.
* ctf-dedup.c (ctf_dedup_emit_type): Set it.
* ctf-link.c (ctf_create_per_cu): Likewise.
(ctf_link_deduplicating_per_cu): Likewise.
(ctf_link): Likewise.
(ctf_link_write): Likewise.
* ctf-subr.c (ctf_dict_set_flag): New function.
(ctf_dict_get_flag): New function.
* ctf-open.c (init_static_types_internal): Move enum tracking to...
* ctf-create.c (ctf_track_enumerator): ... this new function.
(ctf_add_enumerator): Call it.
* libctf.ver: Add the new functions.
* testsuite/libctf-lookup/enumerator-iteration.c: Test them.
libctf, include: new functions for looking up enumerators
Three new functions for looking up the enum type containing a given
enumeration constant, and optionally that constant's value.
The simplest, ctf_lookup_enumerator, looks up a root-visible enumerator by
name in one dict: if the dict contains multiple such constants (which is
possible for dicts created by older versions of the libctf deduplicator),
ECTF_DUPLICATE is returned.
The next simplest, ctf_lookup_enumerator_next, is an iterator which returns
all enumerators with a given name in a given dict, whether root-visible or
not.
The most elaborate, ctf_arc_lookup_enumerator_next, finds all
enumerators with a given name across all dicts in an entire CTF archive,
whether root-visible or not, starting looking in the shared parent dict;
opened dicts are cached (as with all other ctf_arc_*lookup functions) so
that repeated use does not incur repeated opening costs.
All three of these return enumerator values as int64_t: unfortunately, API
compatibility concerns prevent us from doing the same with the other older
enum-related functions, which all return enumerator constant values as ints.
We may be forced to add symbol-versioning compatibility aliases that fix the
other functions in due course, bumping the soname for platforms that do not
support such things.
ctf_arc_lookup_enumerator_next is implemented as a nested ctf_archive_next
iterator, and inside that, a nested ctf_lookup_enumerator_next iterator
within each dict. To aid in this, add support to ctf_next_t iterators for
iterators that are implemented in terms of two simultaneous nested iterators
at once. (It has always been possible for callers to use as many nested or
semi-overlapping ctf_next_t iterators as they need, which is one of the
advantages of this style over the _iter style that calls a function for each
thing iterated over: the iterator change here permits *ctf_next_t iterators
themselves* to be implemented by iterating using multiple other iterators as
part of their internal operation, transparently to the caller.)
Also add a testcase that tests all these functions (which is fairly easy
because ctf_arc_lookup_enumerator_next is implemented in terms of
ctf_lookup_enumerator_next) in addition to enumeration addition in
ctf_open()ed dicts, ctf_add_enumerator duplicate enumerator addition, and
conflicting enumerator constant deduplication.
include/
* ctf-api.h (ctf_lookup_enumerator): New.
(ctf_lookup_enumerator_next): Likewise.
(ctf_arc_lookup_enumerator_next): Likewise.
libctf/
* libctf.ver: Add them.
* ctf-impl.h (ctf_next_t) <ctn_next_inner>: New.
* ctf-util.c (ctf_next_copy): Copy it.
(ctf_next_destroy): Destroy it.
* ctf-lookup.c (ctf_lookup_enumerator): New.
(ctf_lookup_enumerator_next): New.
* ctf-archive.c (ctf_arc_lookup_enumerator_next): New.
* testsuite/libctf-lookup/enumerator-iteration.*: New test.
* testsuite/libctf-lookup/enum-ctf-2.c: New test CTF, used by the
above.
libctf, include: support unnamed structure members better
libctf has no intrinsic support for the GCC unnamed structure member
extension. This principally means that you can't look up named members
inside unnamed struct or union members via ctf_member_info: you have to
tiresomely find out the type ID of the unnamed members via iteration,
then look in each of these.
This is ridiculous. Fix it by extending ctf_member_info so that it
recurses into unnamed members for you: this is still unambiguous because
GCC won't let you create ambiguously-named members even in the presence
of this extension.
For consistency, and because the release hasn't happened and we can
still do this, break the ctf_member_next API and add flags: we specify
one flag, CTF_MN_RECURSE, which if set causes ctf_member_next to
automatically recurse into unnamed members for you, returning not only
the members themselves but all their contained members, so that you can
use ctf_member_next to identify every member that it would be valid to
call ctf_member_info with.
New lookup tests are added for all of this.
include/ChangeLog
2021-01-05 Nick Alcock <nick.alcock@oracle.com>
* ctf-api.h (CTF_MN_RECURSE): New.
(ctf_member_next): Add flags argument.
libctf/ChangeLog
2021-01-05 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (struct ctf_next) <u.ctn_next>: Move to...
<ctn_next>: ... here.
* ctf-util.c (ctf_next_destroy): Unconditionally destroy it.
* ctf-lookup.c (ctf_symbol_next): Adjust accordingly.
* ctf-types.c (ctf_member_iter): Reimplement in terms of...
(ctf_member_next): ... this. Support recursive unnamed member
iteration (off by default).
(ctf_member_info): Look up members in unnamed sub-structs.
* ctf-dedup.c (ctf_dedup_rhash_type): Adjust ctf_member_next call.
(ctf_dedup_emit_struct_members): Likewise.
* testsuite/libctf-lookup/struct-iteration-ctf.c: Test empty unnamed
members, and a normal member after the end.
* testsuite/libctf-lookup/struct-iteration.c: Verify that
ctf_member_count is consistent with the number of successful returns
from a non-recursive ctf_member_next.
* testsuite/libctf-lookup/struct-iteration-*: New, test iteration
over struct members.
* testsuite/libctf-lookup/struct-lookup.c: New test.
* testsuite/libctf-lookup/struct-lookup.lk: New test.
libctf, include: support unnamed structure members better
libctf has no intrinsic support for the GCC unnamed structure member
extension. This principally means that you can't look up named members
inside unnamed struct or union members via ctf_member_info: you have to
tiresomely find out the type ID of the unnamed members via iteration,
then look in each of these.
This is ridiculous. Fix it by extending ctf_member_info so that it
recurses into unnamed members for you: this is still unambiguous because
GCC won't let you create ambiguously-named members even in the presence
of this extension.
For consistency, and because the release hasn't happened and we can
still do this, break the ctf_member_next API and add flags: we specify
one flag, CTF_MN_RECURSE, which if set causes ctf_member_next to
automatically recurse into unnamed members for you, returning not only
the members themselves but all their contained members, so that you can
use ctf_member_next to identify every member that it would be valid to
call ctf_member_info with.
New lookup tests are added for all of this.
include/ChangeLog
2021-01-05 Nick Alcock <nick.alcock@oracle.com>
* ctf-api.h (CTF_MN_RECURSE): New.
(ctf_member_next): Add flags argument.
libctf/ChangeLog
2021-01-05 Nick Alcock <nick.alcock@oracle.com>
* ctf-impl.h (struct ctf_next) <u.ctn_next>: Move to...
<ctn_next>: ... here.
* ctf-util.c (ctf_next_destroy): Unconditionally destroy it.
* ctf-lookup.c (ctf_symbol_next): Adjust accordingly.
* ctf-types.c (ctf_member_iter): Reimplement in terms of...
(ctf_member_next): ... this. Support recursive unnamed member
iteration (off by default).
(ctf_member_info): Look up members in unnamed sub-structs.
* ctf-dedup.c (ctf_dedup_rhash_type): Adjust ctf_member_next call.
(ctf_dedup_emit_struct_members): Likewise.
* testsuite/libctf-lookup/struct-iteration-ctf.c: Test empty unnamed
members, and a normal member after the end.
* testsuite/libctf-lookup/struct-iteration.c: Verify that
ctf_member_count is consistent with the number of successful returns
from a non-recursive ctf_member_next.
* testsuite/libctf-lookup/struct-iteration-*: New, test iteration
over struct members.
* testsuite/libctf-lookup/struct-lookup.c: New test.
* testsuite/libctf-lookup/struct-lookup.lk: New test.