[ARM] 5418/1: restore lr before leaving mcount
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>
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 49a6ba9..159d041 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -111,6 +111,7 @@
.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 @@
.globl ftrace_call
ftrace_call:
bl ftrace_stub
+ ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
#else
@@ -133,6 +135,7 @@
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 @@
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 */
