[PATCH v2] x86: Generate PLT32 relocation for ".long foo@PLT - .L4"

[H.J. Lu]

On Sat, Jul 25, 2026 at 10:35 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> Add BFD_RELOC_X86_64_PLT32 and use it to generate R_X86_64_PLT32 for
> directives like ".long foo@PLT - .L4" so that PLT entries are used to
> resolve the PC32 relocation against function symbols for such directives.
>
> bfd/
>
> PR gas/34423
> * elf64-x86-64.c (x86_64_reloc_map): Add BFD_RELOC_X86_64_PLT32.
> * reloc.c (bfd_reloc_code_real): Add BFD_RELOC_X86_64_PLT32.
> * bfd-in2.h: Regenerated.
> * libbfd.h: Likewise.
>
> gas/
>
> PR gas/34423
> * config/tc-i386.c (x86_cons): Return BFD_RELOC_X86_64_PLT32 for
> directives like ".long foo@PLT - .L4".
> (tc_gen_reloc): Generate R_X86_64_PLT32 for BFD_RELOC_X86_64_PLT32
> with addend computed like R_X86_64_PC32.
> * testsuite/gas/i386/reloc64.l: Updated.
> * testsuite/gas/i386/reloc64.s: Replace ".long xtrn@plt - ." with
> ".long xtrn@plt - _start".
> * testsuite/gas/i386/ilp32/reloc64.l: Updated.
> * testsuite/gas/i386/ilp32/reloc64.s: Replace ".long xtrn@plt - ."
> with ".long xtrn@plt - ptr".
> * testsuite/gas/i386/x86-64-jump-table.d: New file.
> * testsuite/gas/i386/x86-64-jump-table.d: Likewise.
> * testsuite/gas/i386/x86-64-jump-table.s: Likewise.
> * testsuite/gas/i386/x86-64.exp: Run x86-64-jump-table.
> * testsuite/gas/i386/ilp32/x86-64-jump-table.d: New file.
>
> ld/
>
> PR gas/34423
> * testsuite/ld-x86-64/pr34423.c: New file.
> * testsuite/ld-x86-64/x86-64-jump-table.s: Likewise.
> * testsuite/ld-x86-64/x86-64.exp: Run gas/34423 tests.
>

Add i386 support like LLVM assembler in the v2 patch.


-- 
H.J.
---
LLVM assembler supports directives like ".long foo@PLT - .L4" for i386
and x86-64.  Implement the same feature to generate PLT32 relocation
for directives like ".long foo@PLT - .L4" so that PLT entries are used
to resolve the PC32 relocation against function symbols.

bfd/

PR gas/34423
* elf32-i386.c (elf_i386_reloc_type_lookup): Handle
BFD_RELOC_386_PC32_TO_PLT32.
* elf64-x86-64.c (x86_64_reloc_map): Add
BFD_RELOC_X86_64_PC32_TO_PLT32.
* reloc.c (bfd_reloc_code_real): Add BFD_RELOC_386_PC32_TO_PLT32
and BFD_RELOC_X86_64_PC32_TO_PLT32.
* bfd-in2.h: Regenerated.
* libbfd.h: Likewise.

gas/

PR gas/34423
* config/tc-i386.c (x86_cons): Return
BFD_RELOC_X86_64_PC32_TO_PLT32 or BFD_RELOC_386_PC32_TO_PLT32
for directives like ".long foo@PLT - .L4".
(md_apply_fix): Compute addend for BFD_RELOC_386_PC32_TO_PLT32.
(tc_gen_reloc): Handle BFD_RELOC_X86_64_PC32_TO_PLT32 and
BFD_RELOC_386_PC32_TO_PLT32.  Compute addend like
BFD_RELOC_32_PCREL for BFD_RELOC_X86_64_PC32_TO_PLT32.
* testsuite/gas/i386/i386.exp: Run plt test.
* testsuite/gas/i386/ilp32/reloc64.l: Updated.
* testsuite/gas/i386/ilp32/reloc64.s: Replace ".long xtrn@plt - ."
with ".long xtrn@plt - ptr".
* testsuite/gas/i386/ilp32/x86-64-jump-table.d: New file.
* testsuite/gas/i386/plt.d: New file.
* testsuite/gas/i386/plt.s: Likewise.
* testsuite/gas/i386/reloc32.s: Replace ".long xtrn@plt - ."
with ".long xtrn@plt - ptr".
* testsuite/gas/i386/reloc64.l: Updated.
* testsuite/gas/i386/reloc64.s: Replace ".long xtrn@plt - ." with
".long xtrn@plt - _start".
* testsuite/gas/i386/x86-64-jump-table.d: New file.
* testsuite/gas/i386/x86-64-jump-table.d: Likewise.
* testsuite/gas/i386/x86-64-jump-table.s: Likewise.
* testsuite/gas/i386/x86-64.exp: Run x86-64-jump-table.

ld/

PR gas/34423
* testsuite/ld-x86-64/pr34423.c: New file.
* testsuite/ld-x86-64/x86-64-jump-table.s: Likewise.
* testsuite/ld-x86-64/x86-64.exp: Run gas/34423 tests.
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