Messages in this thread Patch in this message | | | Subject | Re: [PATCH v3 16/16] objtool,x86: Rewrite retpoline thunk calls | From | Nathan Chancellor <> | Date | Tue, 8 Jun 2021 09:58:03 -0700 |
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On 6/7/2021 1:54 PM, 'Nick Desaulniers' via Clang Built Linux wrote: > 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
Unfortunately, it does not appear to resolve that issue.
$ git log -2 --decorate=no --oneline eea6a9d6d277 Peter's fix 614124bea77e Linux 5.13-rc5
$ strings /mnt/c/Users/natec/Linux/kernel-investigation | grep microsoft 5.13.0-rc5-microsoft-standard-WSL2-00001-geea6a9d6d277 (nathan@archlinux-ax161) #3 SMP Tue Jun 8 09:46:19 MST 2021
My VM still never makes it to userspace.
>> --- >> 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. >
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