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| author | Steven Rostedt (Red Hat) <rostedt@goodmis.org> | 2014-11-24 17:43:39 +0100 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2014-12-01 20:07:27 +0100 |
| commit | 05df710ec343cf351475e86bfaf89938e5114d69 (patch) | |
| tree | e070c61b5cec0613c37140f664c085cca50c662f /arch/x86/kernel/mcount_64.S | |
| parent | ftrace/x86: Move MCOUNT_SAVE_FRAME out of header file (diff) | |
| download | linux-05df710ec343cf351475e86bfaf89938e5114d69.tar.xz linux-05df710ec343cf351475e86bfaf89938e5114d69.zip | |
ftrace/x86: Rename MCOUNT_SAVE_FRAME and add more detailed comments
The name MCOUNT_SAVE_FRAME is rather confusing as it really isn't a
function frame that is saved, but just the required mcount registers
that are needed to be saved before C code may be called. The word
"frame" confuses it as being a function frame which it is not.
Rename MCOUNT_SAVE_FRAME and MCOUNT_RESTORE_FRAME to save_mcount_regs
and restore_mcount_regs respectively. Noticed the lower case, which
keeps it from screaming at the reviewers.
Link: http://lkml.kernel.org/r/CA+55aFwF+qCGSKdGaEgW4p6N65GZ5_XTV=1NbtWDvxnd5yYLiw@mail.gmail.com
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1411262304010.3961@nanos
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to '')
| -rw-r--r-- | arch/x86/kernel/mcount_64.S | 32 |
1 files changed, 24 insertions, 8 deletions
diff --git a/arch/x86/kernel/mcount_64.S b/arch/x86/kernel/mcount_64.S index 94fe46725fe0..0a693d011980 100644 --- a/arch/x86/kernel/mcount_64.S +++ b/arch/x86/kernel/mcount_64.S @@ -21,8 +21,24 @@ # define function_hook mcount #endif +/* + * gcc -pg option adds a call to 'mcount' in most functions. + * When -mfentry is used, the call is to 'fentry' and not 'mcount' + * and is done before the function's stack frame is set up. + * They both require a set of regs to be saved before calling + * any C code and restored before returning back to the function. + * + * On boot up, all these calls are converted into nops. When tracing + * is enabled, the call can jump to either ftrace_caller or + * ftrace_regs_caller. Callbacks (tracing functions) that require + * ftrace_regs_caller (like kprobes) need to have pt_regs passed to + * it. For this reason, the size of the pt_regs structure will be + * allocated on the stack and the required mcount registers will + * be saved in the locations that pt_regs has them in. + */ + /* skip is set if the stack was already partially adjusted */ -.macro MCOUNT_SAVE_FRAME skip=0 +.macro save_mcount_regs skip=0 /* * We add enough stack to save all regs. */ @@ -39,7 +55,7 @@ movq %rdx, RIP(%rsp) .endm -.macro MCOUNT_RESTORE_FRAME skip=0 +.macro restore_mcount_regs skip=0 movq R9(%rsp), %r9 movq R8(%rsp), %r8 movq RDI(%rsp), %rdi @@ -52,7 +68,7 @@ /* skip is set if stack has been adjusted */ .macro ftrace_caller_setup trace_label skip=0 - MCOUNT_SAVE_FRAME \skip + save_mcount_regs \skip /* Save this location */ GLOBAL(\trace_label) @@ -121,7 +137,7 @@ GLOBAL(ftrace_call) restore_frame - MCOUNT_RESTORE_FRAME + restore_mcount_regs /* * The copied trampoline must call ftrace_return as it @@ -196,7 +212,7 @@ GLOBAL(ftrace_regs_call) movq RBX(%rsp), %rbx /* skip=8 to skip flags saved in SS */ - MCOUNT_RESTORE_FRAME 8 + restore_mcount_regs 8 /* Restore flags */ popfq @@ -240,7 +256,7 @@ trace: call *ftrace_trace_function - MCOUNT_RESTORE_FRAME + restore_mcount_regs jmp fgraph_trace END(function_hook) @@ -249,7 +265,7 @@ END(function_hook) #ifdef CONFIG_FUNCTION_GRAPH_TRACER ENTRY(ftrace_graph_caller) - MCOUNT_SAVE_FRAME + save_mcount_regs #ifdef CC_USING_FENTRY leaq SS+16(%rsp), %rdi @@ -263,7 +279,7 @@ ENTRY(ftrace_graph_caller) call prepare_ftrace_return - MCOUNT_RESTORE_FRAME + restore_mcount_regs retq END(ftrace_graph_caller) |