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ARM: 8678/1: ftrace: Adds support for CONFIG_DYNAMIC_FTRACE_WITH_REGS

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The DYNAMIC_FTRACE_WITH_REGS configuration makes it possible for a
ftrace operation to specify if registers need to saved/restored by
the ftrace handler. This is needed by kgraft and possibly other
ftrace-based tools, and the ARM architecture is currently lacking
this feature. It would also be the first step to support the
"Kprobes-on-ftrace" optimization on ARM.

This patch introduces a new ftrace handler that stores the registers
on the stack before calling the next stage. The registers are restored
from the stack before going back to the instrumented function.

A side-effect of this patch is to activate the support for
ftrace_modify_call() as it defines ARCH_SUPPORTS_FTRACE_OPS for the
ARM architecture.

Signed-off-by: Abel Vesa <abelvesa@linux.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Abel Vesa
2017-05-26 21:49:47 +01:00
committed by Russell King
parent 1515b186c2
commit 620176f335
4 changed files with 142 additions and 0 deletions
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4
arch/arm/include/asm/ftrace.h
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@@ -1,6 +1,10 @@
#ifndef _ASM_ARM_FTRACE
#define _ASM_ARM_FTRACE
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
#define ARCH_SUPPORTS_FTRACE_OPS 1
#endif
#ifdef CONFIG_FUNCTION_TRACER
#define MCOUNT_ADDR ((unsigned long)(__gnu_mcount_nc))
#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */