linux-kernel - Re: objtool failures with -march=atom

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Date:   Wed, 26 Jul 2017 08:55:08 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: objtool failures with -march=atom

On Wed, Jul 26, 2017 at 12:12:04PM +0200, Arnd Bergmann wrote:
> With the latest objtool failure, I get countless warnings when
> -march=atom or -mtune=atom is used,
> at least with gcc-4.9 through gcc-7 (I did not try older versions:
> 
> kernel/sched/core.o: warning: objtool:
> trace_raw_output_sched_stat_runtime()+0x9a: return with modified stack
> frame
> kernel/sched/core.o: warning: objtool: cpu_cgroup_fork()+0x7c: return
> with modified stack frame
> kernel/sched/core.o: warning: objtool: walk_tg_tree_from()+0xd3:
> return with modified stack frame
> kernel/sched/core.o: warning: objtool: ttwu_do_wakeup()+0x2a8: return
> with modified stack frame
> kernel/sched/core.o: warning: objtool: do_set_cpus_allowed()+0x1fe:
> return with modified stack frame
> kernel/sched/core.o: warning: objtool: sched_ttwu_pending()+0xf2:
> return with modified stack frame
> kernel/sched/core.o: warning: objtool: sched_exec()+0xd0: return with
> modified stack frame
> kernel/sched/core.o: warning: objtool: task_sched_runtime()+0x148:
> return with modified stack frame
> kernel/sched/core.o: warning: objtool: sched_move_task()+0x176: return
> with modified stack frame
> kernel/sched/core.o: warning: objtool: sched_init()+0x6cb: return with
> modified stack frame
> 
> Can you have a look?
> 
> There are probably other failures as well, I'm trying to reproduce the
> others now with atom
> optimizations disabled.

Does this fix them all?

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index a36c2eba64e7..4559a21a8de2 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -271,7 +271,7 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 	case 0x8d:
 		if (rex == 0x48 && modrm == 0x65) {
 
-			/* lea -disp(%rbp), %rsp */
+			/* lea disp(%rbp), %rsp */
 			*type = INSN_STACK;
 			op->src.type = OP_SRC_ADD;
 			op->src.reg = CFI_BP;
@@ -281,6 +281,30 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 			break;
 		}
 
+		if (rex == 0x48 && (modrm == 0xa4 || modrm == 0x64) &&
+		    sib == 0x24) {
+
+			/* lea disp(%rsp), %rsp */
+			*type = INSN_STACK;
+			op->src.type = OP_SRC_ADD;
+			op->src.reg = CFI_SP;
+			op->src.offset = insn.displacement.value;
+			op->dest.type = OP_DEST_REG;
+			op->dest.reg = CFI_SP;
+			break;
+		}
+
+		if (rex == 0x48 && modrm == 0x2c && sib == 0x24) {
+
+			/* lea (%rsp), %rbp */
+			*type = INSN_STACK;
+			op->src.type = OP_SRC_REG;
+			op->src.reg = CFI_SP;
+			op->dest.type = OP_DEST_REG;
+			op->dest.reg = CFI_BP;
+			break;
+		}
+
 		if (rex == 0x4c && modrm == 0x54 && sib == 0x24 &&
 		    insn.displacement.value == 8) {