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Code Issues Releases Wiki Activity

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>
This commit is contained in:
Steven Rostedt (Red Hat) 2014-11-24 11:43:39 -05:00 committed by Steven Rostedt
parent 4bcdf1522f
commit 05df710ec3
1 changed files with 24 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
arch/x86/kernel/mcount_64.S
View File

@ -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)