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x86: Check MODRM for call and jmp in binutils older than 2.45

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When i386 glibc was assembled with commit:

commit 11c2852449 (HEAD)
Author: Jan Beulich <jbeulich@suse.com>
Date:   Fri Feb 21 10:24:50 2025 +0100

    x86: widen @got{,pcrel} support to PUSH and APX IMUL

    With us doing the transformation to an immediate operand for MOV and
    various ALU insns, there's little reason to then not support the same
    conversion for the other two insns which have respective immediate
    operand forms. Unfortunately for IMUL (due to the 0F opcode prefix)
    there's no suitable relocation, so the pre-APX forms cannot be marked
    for relaxation in the assembler.

"pushl main@GOT(%ebx)" in sysdeps/i386/start.S was assembled to

1c: ff b3 00 00 00 00 push 0x0(%ebx) 1e: R_386_GOT32X main

Linkers in binutils versions older than 2.45 treated it as jmp and relaxed
it to

22c: e9 cf ff ff ff   jmp    200 <main>
231: 90               nop

Update elf_i386_convert_load_reloc in binutils versions older than 2.45
to check MODRM for call and jmp to work with i386 glibc assembled with
binutils 2.45 or newer.  Do the same in elf_x86_64_convert_load_reloc.

	PR ld/32991
	* elf32-i386.c (elf_i386_convert_load_reloc): Check MODRM for
	call and jmp.
	* elf64-x86-64.c (elf_x86_64_convert_load_reloc): Likewise.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
This commit is contained in:
H.J. Lu
2025-05-22 11:29:49 +08:00
parent b1477053a9
commit 452f551115
2 changed files with 18 additions and 0 deletions
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9
bfd/elf32-i386.c
View File

@@ -1345,6 +1345,15 @@ elf_i386_convert_load_reloc (bfd *abfd, Elf_Internal_Shdr *symtab_hdr,
if (opcode == 0xff)
{
switch (modrm & 0x38)
{
case 0x10: /* CALL */
case 0x20: /* JMP */
break;
default:
return true;
}
/* We have "call/jmp *foo@GOT[(%reg)]". */
if ((h->root.type == bfd_link_hash_defined
|| h->root.type == bfd_link_hash_defweak)

9
bfd/elf64-x86-64.c
View File

@@ -1930,6 +1930,15 @@ elf_x86_64_convert_load_reloc (bfd *abfd,
/* Convert R_X86_64_GOTPCRELX and R_X86_64_REX_GOTPCRELX to
R_X86_64_PC32. */
modrm = bfd_get_8 (abfd, contents + roff - 1);
switch (modrm & 0x38)
{
case 0x10: /* CALL */
case 0x20: /* JMP */
break;
default:
return true;
}
if (modrm == 0x25)
{
/* Convert to "jmp foo nop". */