anchao commented on a change in pull request #5558:
URL: https://github.com/apache/incubator-nuttx/pull/5558#discussion_r825687031
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File path: arch/arm/src/armv7-a/arm_vectors.S
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@@ -239,15 +239,16 @@ arm_vectorirq:
cmp r2, #PSR_MODE_USR /* User mode? */
bne .Lirqleavesvc /* Branch if not user
mode */
+ add sp, sp, #XCPTCONTEXT_SIZE /* Restore SVC's sp */
+
/* ldmia with ^ will return the user mode registers (provided that r15
* is not in the register list).
*/
- mov r13, r0 /* (SVC) R13=Register
storage area */
- ldmia r13, {r0-r12} /* Restore common
R0-R12 */
- add r14, r13, #(4*REG_R13) /* (SVC) R14=address of
R13/R14 storage */
- ldmia r14, {r13, r14}^ /* Restore user mode
R13/R14 */
- add r14, r13, #(4*REG_R15) /* (SVC) R14=address of
R15 storage */
+ mov r14, r0 /* (SVC) r14=Register
storage area */
+ ldmia r14!, {r0-r12} /* Restore common
r0-r12 */
+ ldmia r14, {r13, r14}^ /* Restore user mode
r13/r14 */
Review comment:
https://developer.arm.com/documentation/dui0497/a/BABCAEDD
`The accesses happens in order of increasing register numbers, with the
lowest numbered register using the lowest memory address and the highest number
register using the highest memory address. `
`ldmia r14, {r13, r14, r15}^`
If this syntax is used, R15 will be pushed first, which will immediately
change the PC, and R13 and R14 will not be updated:
```
[ 2.380000] [ 4] [ ALERT] SYSCALL Entry: regs: 0x80202708 cmd: 4
[ 2.380000] [ 4] [ ALERT] R0: 00000004 80001939 00000001 80202018
00000000 00000000 00000000 802027d0
[ 2.380000] [ 4] [ ALERT] R8: 00000000 00000000 00000000 00000000
00000000 802027d0 1080f738 1080f738
[ 2.380000] [ 4] [ ALERT] CPSR: 00000073
[ 2.380000] [ 4] [ ALERT] SYSCALL Exit: regs: 0x80202708
[ 2.380000] [ 4] [ ALERT] R0: 1 80202018 1 80202018 0 0 0 802027d0
[ 2.380000] [ 4] [ ALERT] R8: 0 0 0 0 0 802027d0 1080f738 80001939
[ 2.380000] [ 4] [ ALERT] CPSR: 00000070
[ 2.390000] [ 4] [ EMERG] arm_dataabort: Data abort. PC: 80001938 DFAR:
fffffff8 DFSR: 00000805
[ 2.390000] [ 4] [ EMERG] up_assert: Assertion failed at
file:armv7-a/arm_dataabort.c line: 161 task: /mnt/nfs/bin/init
[ 2.390000] [ 4] [ EMERG] arm_registerdump: R0: 00000001 R1: 80202018 R2:
00000001 R3: 80202018
[ 2.390000] [ 4] [ EMERG] arm_registerdump: R4: 00000000 R5: 00000000 R6:
00000000 FP: 802027d0
[ 2.390000] [ 4] [ EMERG] arm_registerdump: R8: 00000000 SB: 00000000 SL:
00000000 R11: 00000000
[ 2.390000] [ 4] [ EMERG] arm_registerdump: IP: 00000000 SP: 00000000 LR:
00000000 PC: 80001938
```
SP/LR is NULL
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