From d4cc510c61b050ef38e842a12feef71c56d7cf81 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= Date: Wed, 4 Mar 2009 11:48:46 +0100 Subject: [ARM] 5418/1: restore lr before leaving mcount MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 10: e59f0034 ldr r0, [pc, #52] 14: e1a0100e mov r1, lr 18: ebfffffe bl 0 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 Cc: Steven Rostedt Cc: Ingo Molnar Signed-off-by: Uwe Kleine-König Signed-off-by: Russell King --- arch/arm/kernel/entry-common.S | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'arch/arm/kernel') diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index 49a6ba926c2..159d0416f27 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -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 */ -- cgit v1.2.3