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| author | Tom Hughes <tomhughes@chromium.org> | 2021-10-07 22:04:48 +0000 |
|---|---|---|
| committer | Commit Bot <commit-bot@chromium.org> | 2021-11-12 23:47:39 +0000 |
| commit | 1cdedb45fd67ec24df9ac8190ed5f202e35db5e8 (patch) | |
| tree | a3495091a8586de2c1dc8a3ae624caad17f25270 | |
| parent | e1dcf1af5c3af294ed4f69df0f335b37ee769d46 (diff) | |
| download | chrome-ec-1cdedb45fd67ec24df9ac8190ed5f202e35db5e8.tar.gz | |
core/cortex-m: Use symbolic name instead of r0
This assembly is supposed to force the compiler to use r0 for pregs and
r12 for pstack. When compiling with clang, it uses r12 for pregs and r0
for pstack, so the "stmia r0" instruction is using the wrong value.
Instead of assuming that pregs will be in r0 and pstack will be in r12,
just use the symbolic name ("pregs") with the stmia instruction. This
generates the correct behavior regardless of whether pregs or pstack use
r0 or r12.
With gcc, the generated assembly for exception_panic after this change
removes the "mov r0, r0" instruction and adds a nop at the end:
00000000 <exception_panic>:
0: 480e ldr r0, [pc, #56] ; (3c <exception_panic+0x3c>)
2: f8df c03c ldr.w ip, [pc, #60] ; 40 <exception_panic+0x40>
; No more "mov r0, r0" here
6: f3ef 8109 mrs r1, PSP
a: f3ef 8205 mrs r2, IPSR
e: 466b mov r3, sp
10: 05d6 lsls r6, r2, #23
12: bf1c itt ne
14: 2400 movne r4, #0
16: 2500 movne r5, #0
18: f04f 0600 mov.w r6, #0
1c: f04f 0700 mov.w r7, #0
20: f04f 0800 mov.w r8, #0
24: f04f 0900 mov.w r9, #0
28: f04f 0a00 mov.w sl, #0
2c: f04f 0b00 mov.w fp, #0
30: e880 4ffe stmia.w r0, {r1, r2, r3, r4, r5, r6, r7, r8, r9, sl, fp, lr}
34: 46e5 mov sp, ip
36: f7ff fffe bl 0 <exception_panic>
3a: bf00 nop ; adds nop instruction
BRANCH=none
BUG=b:172020503
TEST=CC=clang make BOARD=bloonchipper
TEST=make buildall
Signed-off-by: Tom Hughes <tomhughes@chromium.org>
Change-Id: I150d685bde701171630ae02b16e6050e1e0e77a6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3213606
Reviewed-by: Paul Fagerburg <pfagerburg@chromium.org>
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
| -rw-r--r-- | core/cortex-m/panic.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/core/cortex-m/panic.c b/core/cortex-m/panic.c index fd80061b95..d8e82a4e5d 100644 --- a/core/cortex-m/panic.c +++ b/core/cortex-m/panic.c @@ -363,7 +363,6 @@ void exception_panic(void) { /* Save registers and branch directly to panic handler */ asm volatile( - "mov r0, %[pregs]\n" "mrs r1, psp\n" "mrs r2, ipsr\n" "mov r3, sp\n" @@ -394,7 +393,7 @@ void exception_panic(void) "mov r10, #0\n" "mov r11, #0\n" #endif - "stmia r0, {r1-r11, lr}\n" + "stmia %[pregs], {r1-r11, lr}\n" "mov sp, %[pstack]\n" "bl report_panic\n" : : [pregs] "r" (pdata_ptr->cm.regs), |