Messages in this thread Patch in this message | | | Date | Tue, 07 Aug 2012 15:38:49 -0400 | From | Steven Rostedt <> | Subject | [RFC PATCH 4/4] ftrace/x86: Add support for -mfentry to x86_64 |
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From: Steven Rostedt <srostedt@redhat.com>
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:
<can_vma_merge_before>: 55 push %rbp 48 89 e5 mov %rsp,%rbp 53 push %rbx 41 51 push %r9 e8 fe 6a 39 00 callq ffffffff81483d00 <mcount> 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:
<can_vma_merge_before>: 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.
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Andi Kleen <andi@firstfloor.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- arch/x86/Kconfig | 1 + arch/x86/include/asm/ftrace.h | 7 ++++++- arch/x86/kernel/entry_64.S | 18 +++++++++++++++++- arch/x86/kernel/x8664_ksyms_64.c | 6 +++++- 4 files changed, 29 insertions(+), 3 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index c70684f..bbbf5d8 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 diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h index a6cae0c..9a25b52 100644 --- a/arch/x86/include/asm/ftrace.h +++ b/arch/x86/include/asm/ftrace.h @@ -35,7 +35,11 @@ #endif #ifdef CONFIG_FUNCTION_TRACER -#define MCOUNT_ADDR ((long)(mcount)) +#ifdef CC_USING_FENTRY +# define MCOUNT_ADDR ((long)(__fentry__)) +#else +# define MCOUNT_ADDR ((long)(mcount)) +#endif #define MCOUNT_INSN_SIZE 5 /* sizeof mcount call */ #ifdef CONFIG_DYNAMIC_FTRACE @@ -46,6 +50,7 @@ #ifndef __ASSEMBLY__ extern void mcount(void); extern atomic_t modifying_ftrace_code; +extern void __fentry__(void); static inline unsigned long ftrace_call_adjust(unsigned long addr) { diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 38308fa..2add3bb 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -69,9 +69,16 @@ #ifdef CONFIG_FUNCTION_TRACER #ifdef CONFIG_DYNAMIC_FTRACE + +#ifdef CC_USING_FENTRY +ENTRY(__fentry__) + retq +END(__fentry__) +#else ENTRY(mcount) retq END(mcount) +#endif /* skip is set if stack has been adjusted */ .macro ftrace_caller_setup skip=0 @@ -84,7 +91,11 @@ END(mcount) movq RIP(%rsp), %rdi subq $MCOUNT_INSN_SIZE, %rdi /* Load the parent_ip into the second parameter */ +#ifdef CC_USING_FENTRY + movq SS+16(%rsp), %rsi +#else movq 8(%rbp), %rsi +#endif .endm ENTRY(ftrace_caller) @@ -215,9 +226,14 @@ END(mcount) ENTRY(ftrace_graph_caller) MCOUNT_SAVE_FRAME +#ifdef CC_USING_FENTRY + leaq SS+16(%rsp), %rdi + movq $0, %rdx /* No framepointers needed */ +#else leaq 8(%rbp), %rdi - movq RIP(%rsp), %rsi movq (%rbp), %rdx +#endif + movq RIP(%rsp), %rsi subq $MCOUNT_INSN_SIZE, %rsi call prepare_ftrace_return diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c index 9796c2f..643b236 100644 --- a/arch/x86/kernel/x8664_ksyms_64.c +++ b/arch/x86/kernel/x8664_ksyms_64.c @@ -13,9 +13,13 @@ #include <asm/ftrace.h> #ifdef CONFIG_FUNCTION_TRACER -/* mcount is defined in assembly */ +/* mcount and __fentry__ are defined in assembly */ +#ifdef CC_USING_FENTRY +EXPORT_SYMBOL(__fentry__); +#else EXPORT_SYMBOL(mcount); #endif +#endif EXPORT_SYMBOL(__get_user_1); EXPORT_SYMBOL(__get_user_2); -- 1.7.10.4
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