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>
d4cc510c61