GCC generates an invalid stack frame usage sequence in a function epilogue.
Function prologue with comments:
.align 2
.global rtems_bdbuf_read
.code 16
.thumb_func
.type rtems_bdbuf_read, %function
rtems_bdbuf_read:
push {r4, r5, r6, r7, lr}
sub sp, sp, #60
add r7, sp, #8
/*
* We have now reserved a stack frame in a two step process. The
* non-volatile register r7 will be use as an local variable anchor.
*/
str r3, [r7, #4]
mov r3, #0
str r3, [r7, #48]
str r3, [r7, #44]
str r3, [r7, #40]
mov r3, r7
add r3, r3, #44
str r3, [sp]
sub r3, r3, #4
str r3, [sp, #4]
add r3, r3, #8
bl rtems_bdbuf_obtain_disk
str r0, [r7, #12]
cmp r0, #0
beq .LCB3661
b .L520 @long jump
.LCB3661:
Function epilogue with comments:
.L520:
mov sp, r7
add sp, sp, #52
/*
* Here we released the second part of our stack frame which contains
* local variables.
*/
ldr r0, [r7, #12]
/*
* Here we used the second part of our stack frame which contains local
* variables. We read a status variable from the stack frame that will
* be returned now. That means we use a part of the frame that we
* already released. In case an interrupt happens between these two
* instructions (add and ldr) we may have a big problem. These two
* instructions are in the wrong order, the reverse order is correct.
*/
@ sp needed for prologue
pop {r4, r5, r6, r7, pc}
Attached files follow.
--
Summary: [ARM/Thumb] Invalid stack frame usage at -Os
Product: gcc
Version: 4.4.4
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: sebastian dot huber at embedded-brains dot de
GCC build triplet: x86_64-unknown-linux-gnu
GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: arm-rtems4.10
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44091
