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From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Anton Blanchard <anton@samba.org>,
	linuxppc-dev@lists.ozlabs.org
Subject: [PATCH 3/8] powerpc/ftrace: Remove redundant saving of LR in ftrace[_graph]_caller
Date: Thu,  4 May 2017 10:06:16 +0530	[thread overview]
Message-ID: <96ba8e287a76fe6051215474d5a1ebecf2fd92c7.1493831558.git.naveen.n.rao@linux.vnet.ibm.com> (raw)
In-Reply-To: <cover.1493831558.git.naveen.n.rao@linux.vnet.ibm.com>
In-Reply-To: <cover.1493831558.git.naveen.n.rao@linux.vnet.ibm.com>

For -mprofile-kernel, there is no need to save LR into the ABI save
location on entry into ftrace_caller(). It is sufficient to have the
(possibly updated) return address in LR (and r0?). On return from
ftrace, this value is stored in the ABI save location if necessary.

Furthermore, we can also remove the redundant saving of LR in
ftrace_graph_caller() for similar reasons. It is sufficient to ensure
LR and r0 point to the new return address.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/trace/ftrace_64_mprofile.S | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
index fa0921410fa4..d8d75f4eb853 100644
--- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
+++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
@@ -38,9 +38,6 @@
  * and then arrange for the ftrace function to be called.
  */
 _GLOBAL(ftrace_caller)
-	/* Save the original return address in A's stack frame */
-	std	r0,LRSAVE(r1)
-
 	/* Create our stack frame + pt_regs */
 	stdu	r1,-SWITCH_FRAME_SIZE(r1)
 
@@ -271,6 +268,5 @@ _GLOBAL(ftrace_graph_caller)
 
 	addi	r1, r1, 112
 	mflr	r0
-	std	r0, LRSAVE(r1)
 	bctr
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
-- 
2.12.2

  parent reply	other threads:[~2017-05-04  4:37 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-04  4:36 [PATCH 0/8] powerpc: Various fixes and enhancements for kprobes and ftrace Naveen N. Rao
2017-05-04  4:36 ` [PATCH 1/8] powerpc/kprobes: Pause function_graph tracing during jprobes handling Naveen N. Rao
     [not found]   ` <20170503155819.0cbd04e5@gandalf.local.home>
2017-05-04  4:35     ` Naveen N. Rao
2017-05-04  4:36 ` [PATCH 2/8] powerpc/ftrace: Pass the correct stack pointer for DYNAMIC_FTRACE_WITH_REGS Naveen N. Rao
2017-05-04  4:36 ` Naveen N. Rao [this message]
2017-05-04  4:36 ` [PATCH 4/8] powerpc/kprobes_on_ftrace: Skip livepatch_handler() for jprobes Naveen N. Rao
2017-05-04  4:36 ` [PATCH 5/8] powerpc/ftrace: Eliminate duplicate stack setup for ftrace_graph_caller() Naveen N. Rao
2017-05-04  4:36 ` [PATCH 6/8] powerpc/ftrace: Add support for HAVE_FUNCTION_GRAPH_FP_TEST for -mprofile-kernel Naveen N. Rao
2017-05-04  4:36 ` [PATCH 7/8] powerpc/livepatch: Clarify location of mcount call site Naveen N. Rao
2017-05-04  4:36 ` [PATCH 8/8] powerpc/xmon: Disable function_graph tracing while in xmon Naveen N. Rao

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