From d57c5d51a30152f3175d2344cb6395f08bf8ee0c Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 9 Feb 2011 13:32:18 -0500 Subject: ftrace/x86: Add support for -mfentry to x86_64 If the kernel is compiled with gcc 4.6.0 which supports -mfentry, then use that instead of mcount. With mcount, frame pointers are forced with the -pg option and we get something like: : 55 push %rbp 48 89 e5 mov %rsp,%rbp 53 push %rbx 41 51 push %r9 e8 fe 6a 39 00 callq ffffffff81483d00 31 c0 xor %eax,%eax 48 89 fb mov %rdi,%rbx 48 89 d7 mov %rdx,%rdi 48 33 73 30 xor 0x30(%rbx),%rsi 48 f7 c6 ff ff ff f7 test $0xfffffffff7ffffff,%rsi With -mfentry, frame pointers are no longer forced and the call looks like this: : e8 33 af 37 00 callq ffffffff81461b40 <__fentry__> 53 push %rbx 48 89 fb mov %rdi,%rbx 31 c0 xor %eax,%eax 48 89 d7 mov %rdx,%rdi 41 51 push %r9 48 33 73 30 xor 0x30(%rbx),%rsi 48 f7 c6 ff ff ff f7 test $0xfffffffff7ffffff,%rsi This adds the ftrace hook at the beginning of the function before a frame is set up, and allows the function callbacks to be able to access parameters. As kprobes now can use function tracing (at least on x86) this speeds up the kprobe hooks that are at the beginning of the function. Link: http://lkml.kernel.org/r/20120807194100.130477900@goodmis.org Acked-by: Ingo Molnar Reviewed-by: Masami Hiramatsu Cc: Andi Kleen Signed-off-by: Steven Rostedt --- arch/x86/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/Kconfig') diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index a2d19ee750ca..28dd891a0a16 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -36,6 +36,7 @@ config X86 select HAVE_KRETPROBES select HAVE_OPTPROBES select HAVE_FTRACE_MCOUNT_RECORD + select HAVE_FENTRY if X86_64 select HAVE_C_RECORDMCOUNT select HAVE_DYNAMIC_FTRACE select HAVE_FUNCTION_TRACER -- cgit v1.2.3