From 73d931e560059a87d76f528fafbb4270a98746bc Mon Sep 17 00:00:00 2001
From: Nelson Chu <nelson@rivosinc.com>
Date: Wed, 20 Dec 2023 10:37:41 +0800
Subject: RISC-V: PR31179, The SET/ADD/SUB fix breaks ABI compatibility with
2.41 objects
* Problematic fix commit,
2029e13917d53d2289d3ebb390c4f40bd2112d21
RISC-V: Clarify the behaviors of SET/ADD/SUB relocations
* Bugzilla,
https://sourceware.org/bugzilla/show_bug.cgi?id=31179#c5
The addend of SUB_ULEB128 should be zero if using .uleb128, but we make it
non-zero by accident in assembler before. This causes troubles by applying
the above commit, since the calculation is changed to support .reloc *SUB*
relocations with non-zero addend.
We encourage people to rebuild their stuff to get the non-zero addend of
SUB_ULEB128, but that might need some times, so report warnings to inform
people need to rebuild their stuff if --check-uleb128 is enabled.
Since the failed .reloc cases for ADD/SET/SUB/ULEB128 are rarely to use,
it may acceptable that stop supproting them until people rebuld their stuff,
maybe half-year or a year later. Or maybe we should teach people that don't
write the .reloc R_RISCV_SUB* with non-zero constant, and then report
warnings/errors in assembler.
bfd/
* elfnn-riscv.c (perform_relocation): Ignore the non-zero addend of
R_RISCV_SUB_ULEB128.
(riscv_elf_relocate_section): Report warnings to inform people need
to rebuild their stuff if --check-uleb128 is enabled. So that can
get the right non-zero addend of R_RISCV_SUB_ULEB128.
* elfxx-riscv.h (struct riscv_elf_params): Added bool check_uleb128.
ld/
* NEWS: Updated.
* emultempl/riscvelf.em: Added linker risc-v target options,
--[no-]check-uleb128, to enable/disable checking if the addend of
uleb128 is non-zero or not. So that people will know they need to
rebuild the objects with binutils 2.42 and up, to get the right zero
addend of SUB_ULEB128 relocation, or they may get troubles if using
.reloc.
* ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp: Updated.
* ld/testsuite/ld-riscv-elf/pr31179*: New test cases.
---
bfd/elfxx-riscv.h | 2 ++
1 file changed, 2 insertions(+)
(limited to 'bfd/elfxx-riscv.h')
diff --git a/bfd/elfxx-riscv.h b/bfd/elfxx-riscv.h
index abcb409..6df2471 100644
--- a/bfd/elfxx-riscv.h
+++ b/bfd/elfxx-riscv.h
@@ -31,6 +31,8 @@ struct riscv_elf_params
{
/* Whether to relax code sequences to GP-relative addressing. */
bool relax_gp;
+ /* Whether to check if SUB_ULEB128 relocation has non-zero addend. */
+ bool check_uleb128;
};
extern void riscv_elf32_set_options (struct bfd_link_info *,
--
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