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[ARM] 5418/1: restore lr before leaving mcount

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gcc seems to expect that lr isn't clobbered by mcount, because for a
function starting with:

	static int func(void)
	{
		void *ra = __builtin_return_address(0);

		printk(KERN_EMERG "__builtin_return_address(0) = %pS\n", ra)

		...

the following assembler is generated by gcc 4.3.2:

	   0:   e1a0c00d        mov     ip, sp
	   4:   e92dd810        push    {r4, fp, ip, lr, pc}
	   8:   e24cb004        sub     fp, ip, #4      ; 0x4
	   c:   ebfffffe        bl      0 <mcount>
	  10:   e59f0034        ldr     r0, [pc, #52]
	  14:   e1a0100e        mov     r1, lr
	  18:   ebfffffe        bl      0 <printk>

Without this patch obviously __builtin_return_address(0) yields
func+0x10 instead of the return address of the caller.

Note this patch fixes a similar issue for the routines used with dynamic
ftrace even though this isn't currently selectable for ARM.

Cc: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Uwe Kleine-König 2009-03-04 11:48:46 +01:00 committed by Russell King
parent 843e22b056
commit d4cc510c61
1 changed files with 4 additions and 0 deletions
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4
arch/arm/kernel/entry-common.S
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@ -111,6 +111,7 @@ ENTRY(mcount)
.globl mcount_call
mcount_call:
bl ftrace_stub
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
ENTRY(ftrace_caller)
@ -122,6 +123,7 @@ ENTRY(ftrace_caller)
.globl ftrace_call
ftrace_call:
bl ftrace_stub
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
#else
@ -133,6 +135,7 @@ ENTRY(mcount)
adr r0, ftrace_stub
cmp r0, r2
bne trace
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
trace:
@ -141,6 +144,7 @@ trace:
sub r0, r0, #MCOUNT_INSN_SIZE
mov lr, pc
mov pc, r2
mov lr, r1 @ restore lr
ldmia sp!, {r0-r3, pc}
#endif /* CONFIG_DYNAMIC_FTRACE */