Commit 05df710e authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 4bcdf152

arch/x86/kernel/mcount_64.S

+24 −8
Original line number Diff line number Diff line
@@ -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)

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