Fix multilib error with Xtheadfmv instructions. #6
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RevySR
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Aug 6, 2024
One known missing piece in the modules implementation is merging of a streamed-in local type (class or enum) with the corresponding in-TU version of the local type. This missing piece turns out to cause a hard-to-reduce use-after-free GC issue due to the entity_ary not being marked as a GC root (deliberately), and manifests as a serialization error on stream-in as in PR99426 (see comment #6 for a reduction). It's also reproducible on trunk when running the xtreme-header tests without -fno-module-lazy. This patch implements this missing piece, making us merge such local types according to their position within the containing function's definition, analogous to how we merge FIELD_DECLs of a class according to their index in the TYPE_FIELDS list. PR c++/99426 gcc/cp/ChangeLog: * module.cc (merge_kind::MK_local_type): New enumerator. (merge_kind_name): Update. (trees_out::chained_decls): Move BLOCK-specific handling of DECL_LOCAL_DECL_P decls to ... (trees_out::core_vals) <case BLOCK>: ... here. Stream BLOCK_VARS manually. (trees_in::core_vals) <case BLOCK>: Stream BLOCK_VARS manually. Handle deduplicated local types.. (trees_out::key_local_type): Define. (trees_in::key_local_type): Define. (trees_out::get_merge_kind) <case FUNCTION_DECL>: Return MK_local_type for a local type. (trees_out::key_mergeable) <case FUNCTION_DECL>: Use key_local_type. (trees_in::key_mergeable) <case FUNCTION_DECL>: Likewise. (trees_in::is_matching_decl): Be flexible with type mismatches for local entities. (trees_in::register_duplicate): Also register the DECL_TEMPLATE_RESULT of a TEMPLATE_DECL as a duplicate. (depset_cmp): Return 0 for equal IDENTIFIER_HASH_VALUEs. gcc/testsuite/ChangeLog: * g++.dg/modules/merge-17.h: New test. * g++.dg/modules/merge-17_a.H: New test. * g++.dg/modules/merge-17_b.C: New test. * g++.dg/modules/xtreme-header-7_a.H: New test. * g++.dg/modules/xtreme-header-7_b.C: New test. Reviewed-by: Jason Merrill <[email protected]>
RevySR
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…o_debug_section [PR116614]
cat abc.C
#define A(n) struct T##n {} t##n;
#define B(n) A(n##0) A(n##1) A(n##2) A(n##3) A(n##4) A(n##5) A(n##6) A(n#XUANTIE-RV#7) A(n#XUANTIE-RV#8) A(n#XUANTIE-RV#9)
#define C(n) B(n##0) B(n##1) B(n##2) B(n##3) B(n##4) B(n##5) B(n##6) B(n#XUANTIE-RV#7) B(n#XUANTIE-RV#8) B(n#XUANTIE-RV#9)
#define D(n) C(n##0) C(n##1) C(n##2) C(n##3) C(n##4) C(n##5) C(n##6) C(n#XUANTIE-RV#7) C(n#XUANTIE-RV#8) C(n#XUANTIE-RV#9)
#define E(n) D(n##0) D(n##1) D(n##2) D(n##3) D(n##4) D(n##5) D(n##6) D(n#XUANTIE-RV#7) D(n#XUANTIE-RV#8) D(n#XUANTIE-RV#9)
E(1) E(2) E(3)
int main () { return 0; }
./xg++ -B ./ -o abc{.o,.C} -flto -flto-partition=1to1 -O2 -g -fdebug-types-section -c
./xgcc -B ./ -o abc{,.o} -flto -flto-partition=1to1 -O2
(not included in testsuite as it takes a while to compile) FAILs with
lto-wrapper: fatal error: Too many copied sections: Operation not supported
compilation terminated.
/usr/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status
The following patch fixes that. Most of the 64K+ section support for
reading and writing was already there years ago (and especially reading used
quite often already) and a further bug fixed in it in the PR104617 fix.
Yet, the fix isn't solely about removing the
if (new_i - 1 >= SHN_LORESERVE)
{
*err = ENOTSUP;
return "Too many copied sections";
}
5 lines, the missing part was that the function only handled reading of
the .symtab_shndx section but not copying/updating of it.
If the result has less than 64K-epsilon sections, that actually wasn't
needed, but e.g. with -fdebug-types-section one can exceed that pretty
easily (reported to us on WebKitGtk build on ppc64le).
Updating the section is slightly more complicated, because it basically
needs to be done in lock step with updating the .symtab section, if one
doesn't need to use SHN_XINDEX in there, the section should (or should be
updated to) contain SHN_UNDEF entry, otherwise needs to have whatever would
be overwise stored but couldn't fit. But repeating due to that all the
symtab decisions what to discard and how to rewrite it would be ugly.
So, the patch instead emits the .symtab_shndx section (or sections) last
and prepares the content during the .symtab processing and in a second
pass when going just through .symtab_shndx sections just uses the saved
content.
2024-09-07 Jakub Jelinek <[email protected]>
PR lto/116614
* simple-object-elf.c (SHN_COMMON): Align comment with neighbouring
comments.
(SHN_HIRESERVE): Use uppercase hex digits instead of lowercase for
consistency.
(simple_object_elf_find_sections): Formatting fixes.
(simple_object_elf_fetch_attributes): Likewise.
(simple_object_elf_attributes_merge): Likewise.
(simple_object_elf_start_write): Likewise.
(simple_object_elf_write_ehdr): Likewise.
(simple_object_elf_write_shdr): Likewise.
(simple_object_elf_write_to_file): Likewise.
(simple_object_elf_copy_lto_debug_section): Likewise. Don't fail for
new_i - 1 >= SHN_LORESERVE, instead arrange in that case to copy
over .symtab_shndx sections, though emit those last and compute their
section content when processing associated .symtab sections. Handle
simple_object_internal_read failure even in the .symtab_shndx reading
case.
(cherry picked from commit bb8dd09)
RevySR
pushed a commit
that referenced
this pull request
Jan 1, 2025
…o_debug_section [PR116614]
cat abc.C
#define A(n) struct T##n {} t##n;
#define B(n) A(n##0) A(n##1) A(n##2) A(n##3) A(n##4) A(n##5) A(n##6) A(n#XUANTIE-RV#7) A(n#XUANTIE-RV#8) A(n#XUANTIE-RV#9)
#define C(n) B(n##0) B(n##1) B(n##2) B(n##3) B(n##4) B(n##5) B(n##6) B(n#XUANTIE-RV#7) B(n#XUANTIE-RV#8) B(n#XUANTIE-RV#9)
#define D(n) C(n##0) C(n##1) C(n##2) C(n##3) C(n##4) C(n##5) C(n##6) C(n#XUANTIE-RV#7) C(n#XUANTIE-RV#8) C(n#XUANTIE-RV#9)
#define E(n) D(n##0) D(n##1) D(n##2) D(n##3) D(n##4) D(n##5) D(n##6) D(n#XUANTIE-RV#7) D(n#XUANTIE-RV#8) D(n#XUANTIE-RV#9)
E(1) E(2) E(3)
int main () { return 0; }
./xg++ -B ./ -o abc{.o,.C} -flto -flto-partition=1to1 -O2 -g -fdebug-types-section -c
./xgcc -B ./ -o abc{,.o} -flto -flto-partition=1to1 -O2
(not included in testsuite as it takes a while to compile) FAILs with
lto-wrapper: fatal error: Too many copied sections: Operation not supported
compilation terminated.
/usr/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status
The following patch fixes that. Most of the 64K+ section support for
reading and writing was already there years ago (and especially reading used
quite often already) and a further bug fixed in it in the PR104617 fix.
Yet, the fix isn't solely about removing the
if (new_i - 1 >= SHN_LORESERVE)
{
*err = ENOTSUP;
return "Too many copied sections";
}
5 lines, the missing part was that the function only handled reading of
the .symtab_shndx section but not copying/updating of it.
If the result has less than 64K-epsilon sections, that actually wasn't
needed, but e.g. with -fdebug-types-section one can exceed that pretty
easily (reported to us on WebKitGtk build on ppc64le).
Updating the section is slightly more complicated, because it basically
needs to be done in lock step with updating the .symtab section, if one
doesn't need to use SHN_XINDEX in there, the section should (or should be
updated to) contain SHN_UNDEF entry, otherwise needs to have whatever would
be overwise stored but couldn't fit. But repeating due to that all the
symtab decisions what to discard and how to rewrite it would be ugly.
So, the patch instead emits the .symtab_shndx section (or sections) last
and prepares the content during the .symtab processing and in a second
pass when going just through .symtab_shndx sections just uses the saved
content.
2024-09-07 Jakub Jelinek <[email protected]>
PR lto/116614
* simple-object-elf.c (SHN_COMMON): Align comment with neighbouring
comments.
(SHN_HIRESERVE): Use uppercase hex digits instead of lowercase for
consistency.
(simple_object_elf_find_sections): Formatting fixes.
(simple_object_elf_fetch_attributes): Likewise.
(simple_object_elf_attributes_merge): Likewise.
(simple_object_elf_start_write): Likewise.
(simple_object_elf_write_ehdr): Likewise.
(simple_object_elf_write_shdr): Likewise.
(simple_object_elf_write_to_file): Likewise.
(simple_object_elf_copy_lto_debug_section): Likewise. Don't fail for
new_i - 1 >= SHN_LORESERVE, instead arrange in that case to copy
over .symtab_shndx sections, though emit those last and compute their
section content when processing associated .symtab sections. Handle
simple_object_internal_read failure even in the .symtab_shndx reading
case.
(cherry picked from commit bb8dd09)
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Fix multilib error with Xtheadfmv instructions.