objtool: Fix ORC 'signal' propagation

There have been some recently reported ORC unwinder warnings like:

  WARNING: can't access registers at entry_SYSCALL_64_after_hwframe+0x63/0xcd
  WARNING: stack going in the wrong direction? at __sys_setsockopt+0x2c6/0x5b0 net/socket.c:2271

And a KASAN warning:

  BUG: KASAN: stack-out-of-bounds in unwind_next_frame (arch/x86/include/asm/ptrace.h:136 arch/x86/kernel/unwind_orc.c:455)

It turns out the 'signal' bit isn't getting propagated from the unwind
hints to the ORC entries, making the unwinder confused at times.

Fixes: ffb1b4a4 ("x86/unwind/orc: Add 'signal' field to ORC metadata")
Reported-by: kernel test robot <oliver.sang@intel.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/97eef9db60cd86d376a9a40d49d77bb67a8f6526.1676579666.git.jpoimboe@kernel.org

tools/objtool/check.c

@@ -2330,6 +2330,7 @@ static int read_unwind_hints(struct objtool_file *file)
 
 		cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
 		cfi.type = hint->type;
+		cfi.signal = hint->signal;
 		cfi.end = hint->end;
 
 		insn->cfi = cfi_hash_find_or_add(&cfi);

tools/objtool/include/objtool/cfi.h

@@ -34,6 +34,7 @@ struct cfi_state {
 	unsigned char type;
 	bool bp_scratch;
 	bool drap;
+	bool signal;
 	bool end;
 };
 

tools/objtool/orc_gen.c

@@ -27,6 +27,7 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 	}
 
 	orc->end = cfi->end;
+	orc->signal = cfi->signal;
 
 	if (cfi->cfa.base == CFI_UNDEFINED) {
 		orc->sp_reg = ORC_REG_UNDEFINED;