http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54220
Bug #: 54220
Summary: [avr] Potential stack corruption in naked functions at
-O0
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: senthil_kumar.selva...@atmel.com
Target: AVR
Naked functions do not have a prologue and an epilogue by design, but code
emitted with -O0 for function parameters assume their presence and attempt to
copy values onto the stack. This can corrupt the caller's stack frame.
Note the stores to Y+2 and Y+1 in the example below.
[scratch]$ cat test.c
void __attribute__((naked)) func(int x)
{
__asm volatile ("ret");
}
[scratch]$ avr-gcc -O0 -S test.c
[scratch]$ cat test.s
.file "test.c"
__SREG__ = 0x3f
__SP_H__ = 0x3e
__SP_L__ = 0x3d
__CCP__ = 0x34
__tmp_reg__ = 0
__zero_reg__ = 1
.global __do_copy_data
.global __do_clear_bss
.text
.global func
.type func, @function
func:
/* prologue: naked */
/* frame size = 2 */
/* stack size = 0 */
.L__stack_usage = 0
std Y+2,r25
std Y+1,r24
/* #APP */
; 3 "test.c" 1
ret
; 0 "" 2
/* epilogue start */
/* #NOAPP */
.size func, .-func
