Messages in this thread Patch in this message | | | Date | Fri, 02 Sep 2022 15:06:53 +0200 | From | Peter Zijlstra <> | Subject | [PATCH v2 28/59] objtool: Allow !PC relative relocations |
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From: Peter Zijlstra <peterz@infradead.org>
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) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- tools/objtool/arch/x86/decode.c | 42 +++++++++++++++++++++++++++++----- tools/objtool/check.c | 6 +--- tools/objtool/include/objtool/arch.h | 6 ++-- tools/objtool/include/objtool/check.h | 17 +++++++------ 4 files changed, 51 insertions(+), 20 deletions(-)
--- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -73,6 +73,30 @@ unsigned long arch_jump_destination(stru 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; \ --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1622,7 +1620,7 @@ static int handle_group_alt(struct objto * 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", --- a/tools/objtool/include/objtool/arch.h +++ b/tools/objtool/include/objtool/arch.h @@ -93,4 +91,6 @@ 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 */
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