From 61c6065ef7ec0447a280179d04b2d81c80c2f479 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 15 Sep 2022 13:11:07 +0200 Subject: [PATCH] objtool: Allow !PC relative relocations Objtool doesn't currently much like per-cpu usage in alternatives: arch/x86/entry/entry_64.o: warning: objtool: .altinstr_replacement+0xf: unsupported relocation in alternatives section f: 65 c7 04 25 00 00 00 00 00 00 00 80 movl $0x80000000,%gs:0x0 13: R_X86_64_32S __x86_call_depth Since the R_X86_64_32S relocation is location invariant (it's computation doesn't include P - the address of the location itself), it can be trivially allowed. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20220915111145.806607235@infradead.org --- tools/objtool/arch/x86/decode.c | 24 ++++++++++++++++++++++++ tools/objtool/check.c | 2 +- tools/objtool/include/objtool/arch.h | 2 ++ 3 files changed, 27 insertions(+), 1 deletion(-) diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index 1c253b4..f094383 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -73,6 +73,30 @@ unsigned long arch_jump_destination(struct instruction *insn) return insn->offset + insn->len + insn->immediate; } +bool arch_pc_relative_reloc(struct reloc *reloc) +{ + /* + * All relocation types where P (the address of the target) + * is included in the computation. + */ + switch (reloc->type) { + case R_X86_64_PC8: + case R_X86_64_PC16: + case R_X86_64_PC32: + case R_X86_64_PC64: + + case R_X86_64_PLT32: + case R_X86_64_GOTPC32: + case R_X86_64_GOTPCREL: + return true; + + default: + break; + } + + return false; +} + #define ADD_OP(op) \ if (!(op = calloc(1, sizeof(*op)))) \ return -1; \ diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 43ec14c..7174bba 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1645,7 +1645,7 @@ static int handle_group_alt(struct objtool_file *file, * accordingly. */ alt_reloc = insn_reloc(file, insn); - if (alt_reloc && + if (alt_reloc && arch_pc_relative_reloc(alt_reloc) && !arch_support_alt_relocation(special_alt, insn, alt_reloc)) { WARN_FUNC("unsupported relocation in alternatives section", diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/objtool/arch.h index beb2f3a..fe2ea4b 100644 --- a/tools/objtool/include/objtool/arch.h +++ b/tools/objtool/include/objtool/arch.h @@ -93,4 +93,6 @@ bool arch_is_rethunk(struct symbol *sym); int arch_rewrite_retpolines(struct objtool_file *file); +bool arch_pc_relative_reloc(struct reloc *reloc); + #endif /* _ARCH_H */ -- 2.7.4