Attachment 13809 Details for Bug 28639 – patch for fixing issue

[patch] patch for fixing issue

0001-ignore-build-id-for-linker-inputs-if-new-requested.patch (text/plain), 4.33 KB, created by Valerii Chernous on 2021-11-30 17:00:45 UTC

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Creator: Valerii Chernous

Created: 2021-11-30 17:00:45 UTC

Size: 4.33 KB

patch

obsolete

>From 68d36578e9a840c088e0f73c41416ff9b30cb79b Mon Sep 17 00:00:00 2001
>From: Valerii Chernous <vchernou@cisco.com>
>Date: Thu, 28 Oct 2021 05:19:19 -0700
>Subject: [PATCH] ignore build-id for linker inputs if new requested
>
>Issue description:
>building of glibc 2.32 and later with option "-Wl,--build-id" produce libc.so.6
>with section ".note.gnu.build-id" that have invalid(double, 0x48) section size.
>It happens because glibc use sublibraries for linking libc.so.6
>ld produce this sublibraries with build-id section and on last
>linking stage loads this sections as input for linking.
>ld should create new(valid) ".note.gnu.build-id" into function
>ldelf_setup_build_id on last linking stage but it skip creating because
>build-id section already exists.
>As result libc.so.6 contain ".note.gnu.build-id" with build-ids from
>sublibraries and without valid build-id
>Howto solved:
>Ignoring ".note.gnu.build-id" on linker input fix this problem.
>Linker input doesn't have invalid build-id sections on ldelf_setup_build_id
>stage and create new(proper) one for output library/binary
>
>Clang have it's own fix for this issue:
>https://reviews.llvm.org/D42823
>https://bugs.llvm.org/show_bug.cgi?id=36203
>
>howto reproduce:
>yocto:
>cd GLIBC_RECIPE_WORKDIR
>export CMD_PREFIX="./recipe-sysroot-native/usr/bin/x86_64-iosxe-linux/x86_64-iosxe-linux"; export GCC="$CMD_PREFIX-gcc"; export RELF="$CMD_PREFIX-readelf"
>echo "void f1(){}" >f1.c
>echo "void f2(){}" >f2.c
>$GCC f1.c -c -o f1.o
>$GCC f2.c -c -o f2.o
>$GCC f1.o -Wl,--build-id -nostdlib -nostartfiles -r -o f1
>$GCC f2.o -Wl,--build-id -nostdlib -nostartfiles -r -o f2
>$GCC ./f1 ./f2 -shared -Wl,--build-id -nostdlib -nostartfiles -o f.so
>$RELF -S f.so | grep -E -A1 "note.gnu.bu"
>
>ubuntu:
>echo "void f1(){}" >f1.c
>echo "void f2(){}" >f2.c
>gcc f1.c -c -o f1.o
>gcc f2.c -c -o f2.o
>gcc f1.o -Wl,--build-id -nostdlib -nostartfiles -r -o f1
>gcc f2.o -Wl,--build-id -nostdlib -nostartfiles -r -o f2
>gcc ./f1 ./f2 -shared -Wl,--build-id -nostdlib -nostartfiles -o f.so
>readelf -S f.so | grep -E -A1 "note.gnu.bu"
>
>output:
>without fix
>  [ 1] .note.gnu.bu[...] NOTE             0000000000000238  00000238
>       0000000000000048  0000000000000000   A       0     0     4
>with fix
>  [ 1] .note.gnu.bu[...] NOTE             0000000000000238  00000238
>       0000000000000024  0000000000000000   A       0     0     4
>
>Signed-off-by: Valerii Chernous <vchernou@cisco.com>
>---
> bfd/bfd-in2.h | 2 ++
> bfd/elf.c     | 4 ++++
> ld/ldfile.c   | 5 +++++
> 3 files changed, 11 insertions(+)
>
>diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
>index 7b7a329cd62..5a91e14f6f9 100644
>--- a/bfd/bfd-in2.h
>+++ b/bfd/bfd-in2.h
>@@ -6851,6 +6851,8 @@ struct bfd
> 
>   /* For input BFDs, the build ID, if the object has one. */
>   const struct bfd_build_id *build_id;
>+  /* linker set this flag if create build-id requested by cmd line or default */
>+  int is_new_build_id_requested;
> };
> 
> static inline const char *
>diff --git a/bfd/elf.c b/bfd/elf.c
>index cfdb94922f3..24a1dc44731 100644
>--- a/bfd/elf.c
>+++ b/bfd/elf.c
>@@ -2100,6 +2100,10 @@ bfd_section_from_shdr (bfd *abfd, unsigned int shindex)
>     case SHT_PREINIT_ARRAY:	/* .preinit_array section.  */
>     case SHT_GNU_LIBLIST:	/* .gnu.liblist section.  */
>     case SHT_GNU_HASH:		/* .gnu.hash section.  */
>+
>+    /* skip .note.gnu.build-id section for linker input if create new one requested */
>+      if (hdr->sh_type == SHT_NOTE && abfd->is_linker_input == 1 && abfd->is_new_build_id_requested == 1 && strncmp(name, ".note.gnu.build-id", strlen(".note.gnu.build-id")) == 0 )
>+	goto success;
>       ret = _bfd_elf_make_section_from_shdr (abfd, hdr, name, shindex);
>       goto success;
> 
>diff --git a/ld/ldfile.c b/ld/ldfile.c
>index 22271fd6810..e28cf297057 100644
>--- a/ld/ldfile.c
>+++ b/ld/ldfile.c
>@@ -34,6 +34,7 @@
> #include "ldemul.h"
> #include "libiberty.h"
> #include "filenames.h"
>+#include "ldelf.h"
> #if BFD_SUPPORTS_PLUGINS
> #include "plugin-api.h"
> #include "plugin.h"
>@@ -155,6 +156,10 @@ ldfile_try_open_bfd (const char *attempt,
>     entry->the_bfd->lto_output = 1;
> #endif
> 
>+  /* if new build-id required, inform bfd/elf.c about it */
>+  if (ldelf_emit_note_gnu_build_id != NULL)
>+    entry->the_bfd->is_new_build_id_requested = 1;
>+
>   /* If we are searching for this file, see if the architecture is
>      compatible with the output file.  If it isn't, keep searching.
>      If we can't open the file as an object file, stop the search
>-- 
>2.26.2.Cisco
>

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