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x86/ftrace: Get rid of function_hook

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History lesson courtesy of Steve:

"When ftrace first was introduced to the kernel, it used gcc's
mcount profiling mechanism. The mcount mechanism would add a call to
"mcount" at the start of every function but after the stack frame was
set up. Later, in gcc 4.6, gcc introduced -mfentry, that would create a
call to "__fentry__" instead of "mcount", before the stack frame was
set up. In order to handle both cases, ftrace defined a macro
"function_hook" that would be either "mcount" or "__fentry__" depending
on which one was being used.

The Linux kernel no longer supports the "mcount" method, thus there's
no reason to keep the "function_hook" define around. Simply use
"__fentry__", as there is no ambiguity to the name anymore."

Drop it everywhere.

Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Jiri Slaby <jslaby@suse.cz>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org
Link: http://lkml.kernel.org/r/20191018124800.0a7006bb@gandalf.local.home
This commit is contained in:
Borislav Petkov 2019-10-21 17:18:23 +02:00
parent 13fbe784ef
commit 0f42c1ad44
3 changed files with 11 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
Documentation/asm-annotations.rst
View File

@ -117,9 +117,9 @@ This section covers ``SYM_FUNC_*`` and ``SYM_CODE_*`` enumerated above.
So in most cases, developers should write something like in the following
example, having some asm instructions in between the macros, of course::
SYM_FUNC_START(function_hook)
SYM_FUNC_START(memset)
... asm insns ...
SYM_FUNC_END(function_hook)
SYM_FUNC_END(memset)
In fact, this kind of annotation corresponds to the now deprecated ``ENTRY``
and ``ENDPROC`` macros.

8
arch/x86/kernel/ftrace_32.S
View File

@ -12,18 +12,16 @@
#include <asm/frame.h>
#include <asm/asm-offsets.h>
# define function_hook __fentry__
EXPORT_SYMBOL(__fentry__)
#ifdef CONFIG_FRAME_POINTER
# define MCOUNT_FRAME 1 /* using frame = true */
#else
# define MCOUNT_FRAME 0 /* using frame = false */
#endif
SYM_FUNC_START(function_hook)
SYM_FUNC_START(__fentry__)
ret
SYM_FUNC_END(function_hook)
SYM_FUNC_END(__fentry__)
EXPORT_SYMBOL(__fentry__)
SYM_CODE_START(ftrace_caller)

13
arch/x86/kernel/ftrace_64.S
View File

@ -14,9 +14,6 @@
.code64
.section .entry.text, "ax"
# define function_hook __fentry__
EXPORT_SYMBOL(__fentry__)
#ifdef CONFIG_FRAME_POINTER
/* Save parent and function stack frames (rip and rbp) */
# define MCOUNT_FRAME_SIZE (8+16*2)
@ -132,9 +129,10 @@ EXPORT_SYMBOL(__fentry__)
#ifdef CONFIG_DYNAMIC_FTRACE
SYM_FUNC_START(function_hook)
SYM_FUNC_START(__fentry__)
retq
SYM_FUNC_END(function_hook)
SYM_FUNC_END(__fentry__)
EXPORT_SYMBOL(__fentry__)
SYM_FUNC_START(ftrace_caller)
/* save_mcount_regs fills in first two parameters */
@ -248,7 +246,7 @@ SYM_FUNC_END(ftrace_regs_caller)
#else /* ! CONFIG_DYNAMIC_FTRACE */
SYM_FUNC_START(function_hook)
SYM_FUNC_START(__fentry__)
cmpq $ftrace_stub, ftrace_trace_function
jnz trace
@ -279,7 +277,8 @@ trace:
restore_mcount_regs
jmp fgraph_trace
SYM_FUNC_END(function_hook)
SYM_FUNC_END(__fentry__)
EXPORT_SYMBOL(__fentry__)
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER