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:
<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.
Link: http://lkml.kernel.org/r/20120807194100.130477900@goodmis.org
Acked-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt
Steven Rostedt
parent
781d062482
commit
d57c5d51a3
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@ -36,6 +36,7 @@ config X86
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select HAVE_KRETPROBES
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select HAVE_OPTPROBES
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select HAVE_FTRACE_MCOUNT_RECORD
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select HAVE_FENTRY if X86_64
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select HAVE_C_RECORDMCOUNT
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select HAVE_DYNAMIC_FTRACE
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select HAVE_FUNCTION_TRACER
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@ -35,7 +35,11 @@
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#endif
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#ifdef CONFIG_FUNCTION_TRACER
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#define MCOUNT_ADDR ((long)(mcount))
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#ifdef CC_USING_FENTRY
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# define MCOUNT_ADDR ((long)(__fentry__))
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#else
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# define MCOUNT_ADDR ((long)(mcount))
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#endif
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#define MCOUNT_INSN_SIZE 5 /* sizeof mcount call */
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#ifdef CONFIG_DYNAMIC_FTRACE
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@ -46,6 +50,7 @@
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#ifndef __ASSEMBLY__
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extern void mcount(void);
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extern atomic_t modifying_ftrace_code;
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extern void __fentry__(void);
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static inline unsigned long ftrace_call_adjust(unsigned long addr)
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{
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@ -68,10 +68,18 @@
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.section .entry.text, "ax"
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#ifdef CONFIG_FUNCTION_TRACER
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#ifdef CC_USING_FENTRY
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# define function_hook __fentry__
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#else
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# define function_hook mcount
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#endif
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#ifdef CONFIG_DYNAMIC_FTRACE
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ENTRY(mcount)
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ENTRY(function_hook)
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retq
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END(mcount)
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END(function_hook)
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/* skip is set if stack has been adjusted */
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.macro ftrace_caller_setup skip=0
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@ -84,7 +92,11 @@ END(mcount)
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movq RIP(%rsp), %rdi
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subq $MCOUNT_INSN_SIZE, %rdi
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/* Load the parent_ip into the second parameter */
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#ifdef CC_USING_FENTRY
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movq SS+16(%rsp), %rsi
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#else
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movq 8(%rbp), %rsi
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#endif
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.endm
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ENTRY(ftrace_caller)
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@ -177,7 +189,8 @@ END(ftrace_regs_caller)
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#else /* ! CONFIG_DYNAMIC_FTRACE */
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ENTRY(mcount)
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ENTRY(function_hook)
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cmpl $0, function_trace_stop
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jne ftrace_stub
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@ -199,7 +212,11 @@ trace:
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MCOUNT_SAVE_FRAME
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movq RIP(%rsp), %rdi
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#ifdef CC_USING_FENTRY
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movq SS+16(%rsp), %rsi
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#else
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movq 8(%rbp), %rsi
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#endif
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subq $MCOUNT_INSN_SIZE, %rdi
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call *ftrace_trace_function
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@ -207,7 +224,7 @@ trace:
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MCOUNT_RESTORE_FRAME
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jmp ftrace_stub
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END(mcount)
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END(function_hook)
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#endif /* CONFIG_DYNAMIC_FTRACE */
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#endif /* CONFIG_FUNCTION_TRACER */
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@ -215,9 +232,14 @@ END(mcount)
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ENTRY(ftrace_graph_caller)
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MCOUNT_SAVE_FRAME
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#ifdef CC_USING_FENTRY
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leaq SS+16(%rsp), %rdi
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movq $0, %rdx /* No framepointers needed */
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#else
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leaq 8(%rbp), %rdi
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movq RIP(%rsp), %rsi
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movq (%rbp), %rdx
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#endif
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movq RIP(%rsp), %rsi
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subq $MCOUNT_INSN_SIZE, %rsi
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call prepare_ftrace_return
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@ -13,9 +13,13 @@
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#include <asm/ftrace.h>
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#ifdef CONFIG_FUNCTION_TRACER
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/* mcount is defined in assembly */
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/* mcount and __fentry__ are defined in assembly */
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#ifdef CC_USING_FENTRY
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EXPORT_SYMBOL(__fentry__);
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#else
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EXPORT_SYMBOL(mcount);
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#endif
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#endif
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EXPORT_SYMBOL(__get_user_1);
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EXPORT_SYMBOL(__get_user_2);
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