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| author |   Heiko Carstens <heiko.carstens@de.ibm.com> | 2015-01-09 13:08:28 +0100 |
|---|---|---|
| committer |   Martin Schwidefsky <schwidefsky@de.ibm.com> | 2015-01-29 09:19:25 +0100 |
| commit | e6d60b368b45b9be3aa068f8e5fa98c3487c9d4e (patch) | |
| tree | abe83543f72b5cd5d5de309dab8551f93c34f023 /arch/s390/kernel/mcount.S | |
| parent | ftrace: let notrace function attribute disable hotpatching if necessary (diff) | |
| download | linux-dev-e6d60b368b45b9be3aa068f8e5fa98c3487c9d4e.tar.xz linux-dev-e6d60b368b45b9be3aa068f8e5fa98c3487c9d4e.zip | |
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.S | 2 |
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) |