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ARM: 6314/1: ftrace: allow build without frame pointers on ARM

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With a new enough GCC, ARM function tracing can be supported without the
need for frame pointers.  This is essential for Thumb-2 support, since
frame pointers aren't available then.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Rabin Vincent
2010-08-10 19:32:37 +01:00
committed by Russell King
parent 7e9501fdec
commit 09bfafac3e
4 changed files with 22 additions and 1 deletions
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14
arch/arm/kernel/entry-common.S
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@@ -128,6 +128,13 @@ ENDPROC(ret_from_fork)
* allows it to be clobbered in subroutines and doesn't use it to hold
* parameters.)
*/
#ifndef CONFIG_OLD_MCOUNT
#if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 4))
#error Ftrace requires CONFIG_FRAME_POINTER=y with GCC older than 4.4.0.
#endif
#endif
#ifdef CONFIG_DYNAMIC_FTRACE
ENTRY(mcount)
stmdb sp!, {r0-r3, lr}
@@ -173,6 +180,12 @@ gnu_trace:
ldmia sp!, {r0-r3, ip, lr}
mov pc, ip
#ifdef CONFIG_OLD_MCOUNT
/*
* This is under an ifdef in order to force link-time errors for people trying
* to build with !FRAME_POINTER with a GCC which doesn't use the new-style
* mcount.
*/
ENTRY(mcount)
stmdb sp!, {r0-r3, lr}
ldr r0, =ftrace_trace_function
@@ -191,6 +204,7 @@ trace:
mov pc, r2
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
#endif
#endif /* CONFIG_DYNAMIC_FTRACE */