arm/armv7-a/r: set the default CPU mode to System
In SVC mode, the banked register will be inconsistent with the user mode register:
arch/arm/src/armv7-a/arm_vectors.S
276 .globl arm_syscall
277 .globl arm_vectorsvc
278 .type arm_vectorsvc, %function
279
280 arm_vectorsvc:
...
286 sub sp, sp, #XCPTCONTEXT_SIZE // < SVC mode SP
...
308 stmia r0, {r13, r14}^ // < USR mode SP/LR
...
[ 2.200000] [ 4] [ ALERT] SYSCALL Entry: regs: 0x80202708 cmd: 4
[ 2.200000] [ 4] [ ALERT] R0: 00000004 80001229 00000001 80202018 00000000 00000000 00000000 802027d0
[ 2.200000] [ 4] [ ALERT] R8: 00000000 00000000 00000000 00000000 00000000 802027d0 1080f710 1080f710
[ 2.200000] [ 4] [ ALERT] CPSR: 00000073
[ 2.200000] [ 4] [ ALERT] SYSCALL Exit: regs: 0x80202708
[ 2.200000] [ 4] [ ALERT] R0: 1 80202018 1 80202018 0 0 0 802027d0
[ 2.200000] [ 4] [ ALERT] R8: 0 0 0 0 0 802027d0 1080f710 80001229
[ 2.200000] [ 4] [ ALERT] CPSR: 00000070
SVC SP is 0x80202708
USR SP is 0x802027d0
0x802027d0 - 0x80202708 should be XCPTCONTEXT_SIZE
[ 2.200000] [ 4] [ ALERT] SYSCALL Entry: regs: 0x80202708 cmd: 51
[ 2.200000] [ 4] [ ALERT] R0: 00000033 00000000 80202780 00000000 00000000 00000000 00000000 80202710
[ 2.200000] [ 4] [ ALERT] R8: 00000000 00000000 00000000 00000000 00000000 80202710 800039d5 800039b2
[ 2.200000] [ 4] [ ALERT] CPSR: 00000070
[ 2.200000] [ 4] [ ALERT] SYSCALL Exit: regs: 0x80202708
[ 2.200000] [ 4] [ ALERT] R0: 2b 0 80202780 0 0 0 0 80202710
[ 2.200000] [ 4] [ ALERT] R8: 0 0 0 0 0 10843d80 800039d5 10801425
[ 2.200000] [ 4] [ ALERT] CPSR: 00000073
SVC SP is 0x80202708
USR SP is 0x80202710
SP overlap in SVC and USR mode
This commit change the default CPU mode to System and ensure the consistency of SP/LR in USR/SYS mode during syscall.
Signed-off-by: chao.an <anchao@xiaomi.com>
7c02432f0e