Commit 0f42c1ad authored by Borislav Petkov's avatar Borislav Petkov
Browse files

x86/ftrace: Get rid of function_hook 



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: default avatarBorislav Petkov <bp@suse.de>
Acked-by: default avatarJiri 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
parent 13fbe784

Documentation/asm-annotations.rst

+2 −2
Original line number Diff line number Diff line
@@ -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.

arch/x86/kernel/ftrace_32.S

+3 −5
Original line number Diff line number Diff line
@@ -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)

arch/x86/kernel/ftrace_64.S

+6 −7
Original line number Diff line number Diff line
@@ -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

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