| Message ID | 14455987.OWjnZpEEup@wuerfel (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Dec 2, 2016 at 2:55 AM, Arnd Bergmann <arnd@arndb.de> wrote: > > Yes, it's always been just the assembly symbols that broke, these were > the ones that Al's original patch changed and that ended up with > no version information. Ok, and the reason is because even if we have a weak symbol from C, it would always have a value. Good to know what the heck the problem was. > I have managed to bisect the link failure to a specific binutils > commit by Alan Modra now: Thanks. And I committed your "set to zero" patch, so we can hopefully leave this all behind us. I marked it for stable (not because older kernels need it, but because it's the right thing to do and if we ever backport anything that causes this we don't want to forget this). And I'll keep the workaround in kernel/module.c just because it's really late in the rc series, and I'd rather have both belt and suspenders for this all right now. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Dec 02, 2016 at 11:55:58AM +0100, Arnd Bergmann wrote: > I have managed to bisect the link failure to a specific binutils > commit by Alan Modra now: > > d983c8c ("Strip undefined symbols from .symtab") > > went into binutils-2_26 and was reverted in > > a82e3ef ("Revert "Strip undefined symbols from .symtab"") > > after the release branch for 2.26 was started, so that version > ended up being fine. However, the 2.27 version never saw the revert > and causes loadable kernel modules to become unusable when they refer > to a weak symbol in vmlinux. This works with 2.26 and lower: See https://sourceware.org/ml/binutils/2016-01/msg00118.html thread for discussion on why the patch was reverted for 2.26. At the time I believed that only the ppc64 kernel was affected, by a weak undefined "__crc_TOC." disappearing. Am I correct in thinking that remained true up until Linus' merge commit 84d69848c9 2016-10-14? As far as reverting the binutils commit goes, I'm quite willing to do that if necessary. You can see how important I think the fix was by viewing https://sourceware.org/bugzilla/show_bug.cgi?id=4317 and noticing that the bug was reported in 2007 and didn't see any action for 8 years..
On Sat, Dec 3, 2016 at 11:44 PM, Alan Modra <amodra@gmail.com> wrote: > > As far as reverting the binutils commit goes, I'm quite willing to do > that if necessary I think we have the proper fix in the kernel now, witht he "mark weak asm symbols with value 0". Or if not "proper", then at least acceptable. So I think the ship has sailed on the binutils change, and there's no point in reverting it any more. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/bfd/elflink.c b/bfd/elflink.c index 5f87f87..57c4d42 100644 --- a/bfd/elflink.c +++ b/bfd/elflink.c @@ -9354,9 +9354,8 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data) a regular file, or that we have been told to strip. However, if h->indx is set to -2, the symbol is used by a reloc and we must output it. */ - strip = FALSE; if (h->indx == -2) - ; + strip = FALSE; else if ((h->def_dynamic || h->ref_dynamic || h->root.type == bfd_link_hash_new) @@ -9382,13 +9381,14 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data) && h->root.u.undef.abfd != NULL && (h->root.u.undef.abfd->flags & BFD_PLUGIN) != 0) strip = TRUE; + else + strip = FALSE; type = h->type; /* If we're stripping it, and it's not a dynamic symbol, there's - nothing else to do. However, if it is a forced local symbol or - an ifunc symbol we need to give the backend finish_dynamic_symbol - function a chance to make it dynamic. */ + nothing else to do unless it is a forced local symbol or a + STT_GNU_IFUNC symbol. */ if (strip && h->dynindx == -1 && type != STT_GNU_IFUNC @@ -9691,18 +9691,9 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data) } } - /* If the symbol is undefined, and we didn't output it to .dynsym, - strip it from .symtab too. Obviously we can't do this for - relocatable output or when needed for --emit-relocs. */ - else if (input_sec == bfd_und_section_ptr - && h->indx != -2 - && !bfd_link_relocatable (flinfo->info)) - return TRUE; - /* Also strip others that we couldn't earlier due to dynamic symbol - processing. */ - if (strip) - return TRUE; - if ((input_sec->flags & SEC_EXCLUDE) != 0) + /* If we're stripping it, then it was just a dynamic symbol, and + there's nothing else to do. */ + if (strip || (input_sec->flags & SEC_EXCLUDE) != 0) return TRUE; /* Output a FILE symbol so that following locals are not associated @@ -9952,9 +9943,8 @@ elf_link_input_bfd (struct elf_final_link_info *flinfo, bfd *input_bfd) *ppsection = isec; - /* Don't output the first, undefined, symbol. In fact, don't - output any undefined local symbol. */ - if (isec == bfd_und_section_ptr) + /* Don't output the first, undefined, symbol. */ + if (ppsection == flinfo->sections) continue; if (ELF_ST_TYPE (isym->st_info) == STT_SECTION)