[PATCH 11/13] objtool: Rewrite jump_label instructions

From: Peter Zijlstra
Date: Thu May 06 2021 - 15:42:56 EST


When a jump_entry::key has bit1 set, rewrite the instruction to be a
NOP. This allows the compiler/assembler to emit JMP (and thus decide
on which encoding to use).

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
tools/objtool/check.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1223,6 +1223,20 @@ static int handle_jump_alt(struct objtoo
return -1;
}

+ if (special_alt->key_addend & 2) {
+ struct reloc *reloc = insn_reloc(file, orig_insn);
+
+ if (reloc) {
+ reloc->type = R_NONE;
+ elf_write_reloc(file->elf, reloc);
+ }
+ elf_write_insn(file->elf, orig_insn->sec,
+ orig_insn->offset, orig_insn->len,
+ arch_nop_insn(orig_insn->len));
+ orig_insn->type = INSN_NOP;
+ return 0;
+ }
+
*new_insn = list_next_entry(orig_insn, list);
return 0;
}