Messages in this thread | | | From | Nick Desaulniers <> | Date | Mon, 7 Jun 2021 13:54:37 -0700 | Subject | Re: [PATCH v3 16/16] objtool,x86: Rewrite retpoline thunk calls |
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On Mon, Jun 7, 2021 at 2:46 AM Peter Zijlstra <peterz@infradead.org> wrote: >
Thanks, the below diff resolves the linker error reported in https://github.com/ClangBuiltLinux/linux/issues/1388
Both readelf implementations seem happy with the results, too.
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Nathan, Can you please test the below diff and see if that resolves your boot issue reported in: https://github.com/ClangBuiltLinux/linux/issues/1384
> --- > tools/objtool/elf.c | 25 ++++++++++++++++++++++++- > 1 file changed, 24 insertions(+), 1 deletion(-) > > diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c > index 743c2e9d0f56..41bca1d13d8e 100644 > --- a/tools/objtool/elf.c > +++ b/tools/objtool/elf.c > @@ -717,7 +717,7 @@ static int elf_add_string(struct elf *elf, struct section *strtab, char *str) > > struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name) > { > - struct section *symtab; > + struct section *symtab, *symtab_shndx; > struct symbol *sym; > Elf_Data *data; > Elf_Scn *s; > @@ -769,6 +769,29 @@ struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name) > symtab->len += data->d_size; > symtab->changed = true; > > + symtab_shndx = find_section_by_name(elf, ".symtab_shndx"); > + if (symtab_shndx) { > + s = elf_getscn(elf->elf, symtab_shndx->idx); > + if (!s) { > + WARN_ELF("elf_getscn"); > + return NULL; > + } > + > + data = elf_newdata(s); > + if (!data) { > + WARN_ELF("elf_newdata"); > + return NULL; > + } > + > + data->d_buf = &sym->sym.st_size; /* conveniently 0 */ > + data->d_size = sizeof(Elf32_Word); > + data->d_align = 4; > + data->d_type = ELF_T_WORD; > + > + symtab_shndx->len += 4; > + symtab_shndx->changed = true; > + } > + > sym->sec = find_section_by_index(elf, 0); > > elf_add_symbol(elf, sym);
The only thing that's still different is that the `file` command still prints "no section header."
$ find . -name \*.lto.o | xargs file | rev | cut -d , -f 1 | rev | sort | uniq -c 1 no section header 8377 not stripped 1 too many section headers (33683) 1 too many section headers (50758) $ file --version file-5.39
That's drivers/gpu/drm/amd/amdgpu/amdgpu.lto.o, fs/xfs/xfs.lto.o, drivers/gpu/drm/i915/i915.lto.o, respectively. I'm not sure that's a problem, yet, and whether 9bc0bb50727c8ac69fbb33fb937431cf3518ff37 is even related yet; those might just be huge drivers and figured it was reporting somewhere in case it ever comes up again. CONFIG_LTO implies -ffunction-sections -fdata-sections, and CONFIG_LD_DEAD_CODE_DATA_ELIMINATION explicitly sets those, too. -- Thanks, ~Nick Desaulniers
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