From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
tglx@linutronix.de, linux-kernel@vger.kernel.org, x86@kernel.org,
mhiramat@kernel.org, mbenes@suse.cz
Subject: [RFC][PATCH] x86,ftrace: Shrink ftrace_regs_caller() by one byte
Date: Tue, 31 Mar 2020 18:06:39 +0200 [thread overview]
Message-ID: <20200331160639.GV20730@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200331113136.01316614@gandalf.local.home>
On Tue, Mar 31, 2020 at 11:31:36AM -0400, Steven Rostedt wrote:
> On Tue, 31 Mar 2020 13:16:52 +0200
> Peter Zijlstra <peterz@infradead.org> wrote:
>
> > @@ -235,8 +237,8 @@ SYM_INNER_LABEL(ftrace_regs_call, SYM_L_GLOBAL)
> >
> > /* If ORIG_RAX is anything but zero, make this a call to that */
> > movq ORIG_RAX(%rsp), %rax
> > - cmpq $0, %rax
> > - je 1f
> > + testq %rax, %rax
> > + jz 1f
> >
> > /* Swap the flags with orig_rax */
> > movq MCOUNT_REG_SIZE(%rsp), %rdi
>
> Hi Peter,
>
> Can you send this change as a separate patch as it has nothing to do with
> this current change, and is a clean up patch that stands on its own.
Sure. But then I have to like write a Changelog for it... :/
---
Subject: x86,ftrace: Shrink ftrace_regs_caller() by one byte
'Optimize' ftrace_regs_caller. Instead of comparing against an
immediate, the more natural way to test for zero on x86 is: 'test
%r,%r'.
48 83 f8 00 cmp $0x0,%rax
74 49 je 226 <ftrace_regs_call+0xa3>
48 85 c0 test %rax,%rax
74 49 je 225 <ftrace_regs_call+0xa2>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/kernel/ftrace_64.S | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
index 369e61faacfe..8e71c492d623 100644
--- a/arch/x86/kernel/ftrace_64.S
+++ b/arch/x86/kernel/ftrace_64.S
@@ -235,8 +235,8 @@ SYM_INNER_LABEL(ftrace_regs_call, SYM_L_GLOBAL)
/* If ORIG_RAX is anything but zero, make this a call to that */
movq ORIG_RAX(%rsp), %rax
- cmpq $0, %rax
- je 1f
+ testq %rax, %rax
+ jz 1f
/* Swap the flags with orig_rax */
movq MCOUNT_REG_SIZE(%rsp), %rdi
next prev parent reply other threads:[~2020-03-31 16:06 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-25 17:45 [PATCH v4 00/13] objtool: vmlinux.o and moinstr validation Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 01/13] objtool: Remove CFI save/restore special case Peter Zijlstra
2020-03-26 11:30 ` Peter Zijlstra
2020-03-26 12:58 ` Peter Zijlstra
2020-03-26 13:44 ` Josh Poimboeuf
2020-03-26 15:38 ` Peter Zijlstra
2020-03-27 4:19 ` Josh Poimboeuf
2020-03-26 14:44 ` Miroslav Benes
2020-03-26 15:04 ` Miroslav Benes
2020-03-26 13:00 ` Peter Zijlstra
2020-03-26 13:56 ` Josh Poimboeuf
2020-03-26 15:49 ` Peter Zijlstra
2020-03-26 19:57 ` Peter Zijlstra
2020-03-27 1:00 ` Josh Poimboeuf
2020-03-30 17:02 ` Peter Zijlstra
2020-03-30 19:02 ` Josh Poimboeuf
2020-03-30 20:02 ` Peter Zijlstra
2020-03-30 20:29 ` Peter Zijlstra
2020-03-31 11:16 ` [RFC][PATCH] objtool,ftrace: Implement UNWIND_HINT_RET_OFFSET Peter Zijlstra
2020-03-31 15:31 ` Steven Rostedt
2020-03-31 16:06 ` Peter Zijlstra [this message]
2020-03-31 19:58 ` Peter Zijlstra
2020-03-31 20:26 ` Josh Poimboeuf
2020-03-31 20:23 ` Josh Poimboeuf
2020-03-31 20:40 ` Peter Zijlstra
2020-03-31 21:07 ` Peter Zijlstra
2020-03-31 21:17 ` Josh Poimboeuf
2020-03-31 21:20 ` Josh Poimboeuf
2020-03-31 22:27 ` [PATCH v2] " Peter Zijlstra
2020-04-01 14:14 ` Josh Poimboeuf
2020-04-01 14:22 ` Peter Zijlstra
2020-04-01 14:39 ` Josh Poimboeuf
2020-04-01 15:38 ` Peter Zijlstra
2020-04-01 15:39 ` Steven Rostedt
2020-04-01 15:43 ` Julien Thierry
2020-04-01 17:09 ` Peter Zijlstra
2020-04-01 17:33 ` Steven Rostedt
2020-04-01 17:45 ` Peter Zijlstra
2020-04-01 18:20 ` Steven Rostedt
2020-04-01 20:20 ` Peter Zijlstra
2020-04-01 17:37 ` Josh Poimboeuf
2020-04-02 6:41 ` Julien Thierry
2020-04-02 6:56 ` Julien Thierry
2020-04-02 7:50 ` Peter Zijlstra
2020-04-02 8:16 ` Julien Thierry
2020-04-02 8:17 ` Peter Zijlstra
2020-04-02 8:29 ` Julien Thierry
2020-04-02 8:58 ` Miroslav Benes
2020-03-25 17:45 ` [PATCH v4 02/13] objtool: Factor out CFI hints Peter Zijlstra
2020-03-25 18:26 ` Miroslav Benes
2020-03-25 19:41 ` Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 03/13] objtool: Rename struct cfi_state Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 04/13] objtool: Fix !CFI insn_state propagation Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 05/13] objtool: Implement noinstr validation Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 06/13] objtool: Optimize !vmlinux.o again Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 07/13] objtool: Use sec_offset_hash() for insn_hash Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 08/13] objtool: Detect loading function pointers across noinstr Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 09/13] kbuild/objtool: Add objtool-vmlinux.o pass Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 10/13] objtool: Avoid iterating !text section symbols Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 11/13] objtool: Rearrange validate_section() Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 12/13] objtool: Add STT_NOTYPE noinstr validation Peter Zijlstra
2020-03-25 17:45 ` [PATCH v4 13/13] objtool: Also consider .entry.text as noinstr Peter Zijlstra
2020-03-25 19:03 ` [PATCH v4 00/13] objtool: vmlinux.o and moinstr validation Miroslav Benes
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