diff options
| author | AKASHI Takahiro <takahiro.akashi@linaro.org> | 2014-04-30 10:54:34 +0100 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2014-05-29 09:08:33 +0100 |
| commit | bd7d38dbdf356e75eb3b1699158c9b8021fd6784 (patch) | |
| tree | edad0afa91c1774cfaba6319b319d65db244123d /arch/arm64/kernel/entry-ftrace.S | |
| parent | 819e50e25d0ce8a75f5cba815416a6a8573655c4 (diff) | |
arm64: ftrace: Add dynamic ftrace support
This patch allows "dynamic ftrace" if CONFIG_DYNAMIC_FTRACE is enabled.
Here we can turn on and off tracing dynamically per-function base.
On arm64, this is done by patching single branch instruction to _mcount()
inserted by gcc -pg option. The branch is replaced to NOP initially at
kernel start up, and later on, NOP to branch to ftrace_caller() when
enabled or branch to NOP when disabled.
Please note that ftrace_caller() is a counterpart of _mcount() in case of
'static' ftrace.
More details on architecture specific requirements are described in
Documentation/trace/ftrace-design.txt.
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel/entry-ftrace.S')
| -rw-r--r-- | arch/arm64/kernel/entry-ftrace.S | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S index b2d8c4559cd8..b051871f2965 100644 --- a/arch/arm64/kernel/entry-ftrace.S +++ b/arch/arm64/kernel/entry-ftrace.S @@ -86,6 +86,7 @@ add \reg, \reg, #8 .endm +#ifndef CONFIG_DYNAMIC_FTRACE /* * void _mcount(unsigned long return_address) * @return_address: return address to instrumented function @@ -134,6 +135,48 @@ skip_ftrace_call: #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ ENDPROC(_mcount) +#else /* CONFIG_DYNAMIC_FTRACE */ +/* + * _mcount() is used to build the kernel with -pg option, but all the branch + * instructions to _mcount() are replaced to NOP initially at kernel start up, + * and later on, NOP to branch to ftrace_caller() when enabled or branch to + * NOP when disabled per-function base. + */ +ENTRY(_mcount) + ret +ENDPROC(_mcount) + +/* + * void ftrace_caller(unsigned long return_address) + * @return_address: return address to instrumented function + * + * This function is a counterpart of _mcount() in 'static' ftrace, and + * makes calls to: + * - tracer function to probe instrumented function's entry, + * - ftrace_graph_caller to set up an exit hook + */ +ENTRY(ftrace_caller) + mcount_enter + + mcount_get_pc0 x0 // function's pc + mcount_get_lr x1 // function's lr + + .global ftrace_call +ftrace_call: // tracer(pc, lr); + nop // This will be replaced with "bl xxx" + // where xxx can be any kind of tracer. + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + .global ftrace_graph_call +ftrace_graph_call: // ftrace_graph_caller(); + nop // If enabled, this will be replaced + // "b ftrace_graph_caller" +#endif + + mcount_exit +ENDPROC(ftrace_caller) +#endif /* CONFIG_DYNAMIC_FTRACE */ + ENTRY(ftrace_stub) ret ENDPROC(ftrace_stub) |