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authorHeiko Carstens <heiko.carstens@de.ibm.com>2015-01-09 13:08:28 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2015-01-29 09:19:25 +0100
commite6d60b368b45b9be3aa068f8e5fa98c3487c9d4e (patch)
treeabe83543f72b5cd5d5de309dab8551f93c34f023 /arch/s390/kernel/mcount.S
parent61f552141c9c0e88b3fdc7046265781ffd8fa68a (diff)
s390/ftrace: hotpatch support for function tracing
Make use of gcc's hotpatch support to generate better code for ftrace function tracing. The generated code now contains only a six byte nop in each function prologue instead of a 24 byte code block which will be runtime patched to support function tracing. With the new code generation the runtime overhead for supporting function tracing is close to zero, while the original code did show a significant performance impact. Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/mcount.S')
-rw-r--r--arch/s390/kernel/mcount.S2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S
index b6dfc5bfcb89..e499370fbccb 100644
--- a/arch/s390/kernel/mcount.S
+++ b/arch/s390/kernel/mcount.S
@@ -27,7 +27,9 @@ ENTRY(ftrace_caller)
.globl ftrace_regs_caller
.set ftrace_regs_caller,ftrace_caller
lgr %r1,%r15
+#ifndef CC_USING_HOTPATCH
aghi %r0,MCOUNT_RETURN_FIXUP
+#endif
aghi %r15,-STACK_FRAME_SIZE
stg %r1,__SF_BACKCHAIN(%r15)
stg %r1,(STACK_PTREGS_GPRS+15*8)(%r15)