From: Borislav Petkov <[email protected]> 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 <[email protected]> Acked-by: Jiri Slaby <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: [email protected] Cc: [email protected] Cc: Peter Zijlstra <[email protected]> Cc: "Steven Rostedt (VMware)" <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] --- Documentation/asm-annotations.rst | 4 ++-- arch/x86/kernel/ftrace_32.S | 8 +++----- arch/x86/kernel/ftrace_64.S | 13 ++++++------- 3 files changed, 11 insertions(+), 14 deletions(-) diff --git a/Documentation/asm-annotations.rst b/Documentation/asm-annotations.rst index 29ccd6e61fe5..f55c2bb74d00 100644 --- a/Documentation/asm-annotations.rst +++ b/Documentation/asm-annotations.rst @@ -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. diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S index 8ed1f5d371f0..e8a9f8370112 100644 --- a/arch/x86/kernel/ftrace_32.S +++ b/arch/x86/kernel/ftrace_32.S @@ -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) diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S index 69c8d1b9119e..6e8961ca3605 100644 --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -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 -- 2.21.0 -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
