path: root/arch/s390/kernel/kprobes.c
diff options
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/kprobes.c
parentftrace: let notrace function attribute disable hotpatching if necessary (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/kprobes.c')
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index 1e4c710dfb92..f516edc1fbe3 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -69,7 +69,8 @@ static void copy_instruction(struct kprobe *p)
* If kprobes patches the instruction that is morphed by
* ftrace make sure that kprobes always sees the branch
- * "jg .+24" that skips the mcount block
+ * "jg .+24" that skips the mcount block or the "brcl 0,0"
+ * in case of hotpatch.
ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
p->ainsn.is_ftrace_insn = 1;