ARMv7-A: Modify up_fullcontextrestore() for CONFIG_BUILD_KERNEL. It changed CPSR while in kernel. That will crash is the new CPSR is user mode while executing in kernel space. Fixed by adding a SYS_context_restore system call. There is an alternative, simpler modification to up_fullcontextrestore() that could have been done: It might have been possible to use the SPSR instead of the CPRSR and then do an exception return from up_fullcontextrestore(). That would be more efficient, but I never tried it.
This commit is contained in:
Gregory Nutt
parent
5a96bc37e4
commit
f8170550e1
@ -37,8 +37,10 @@
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <nuttx/irq.h>
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#include "up_internal.h"
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#include "svcall.h"
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.file "arm_fullcontextrestore.S"
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@ -112,6 +114,28 @@ up_fullcontextrestore:
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vmsr fpscr, r2 /* Restore the FPCSR */
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#endif
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#ifdef CONFIG_BUILD_KERNEL
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/* For the kernel build, we need to be able to transition gracefully
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* between kernel- and user-mode tasks. We have to do that with a system
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* call; the system call will execute in kernel mode and but can return
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* to either user or kernel mode.
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*/
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/* Perform the System call with R0=SYS_context_restore, R1=restoreregs */
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mov r1, r0 /* R1: restoreregs */
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mov r0, #SYS_context_restore /* R0: SYS_context_restore syscall */
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svc #0x900001 /* Perform the system call */
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/* This call should not return */
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bx lr /* Unnecessary ... will not return */
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#else
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/* For a flat build, we can do all of this here... Just think of this as
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* a longjmp() all on steriods.
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*/
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/* Recover all registers except for r0, r1, R15, and CPSR */
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add r1, r0, #(4*REG_R2) /* Offset to REG_R2 storage */
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@ -148,4 +172,7 @@ up_fullcontextrestore:
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*/
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ldr pc, [sp], #4
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#endif
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.size up_fullcontextrestore, . - up_fullcontextrestore
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@ -58,16 +58,16 @@
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****************************************************************************/
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/* Debug ********************************************************************/
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/* Output debug info if stack dump is selected -- even if
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* debug is not selected.
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*/
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#if defined(CONFIG_DEBUG_SYSCALL) || defined(CONFIG_DEBUG_SVCALL)
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#if defined(CONFIG_DEBUG_SYSCALL)
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# define svcdbg(format, ...) lldbg(format, ##__VA_ARGS__)
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#else
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# define svcdbg(x...)
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#endif
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/* Output debug info if stack dump is selected -- even if debug is not
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* selected.
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*/
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#ifdef CONFIG_ARCH_STACKDUMP
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# undef lldbg
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# define lldbg lowsyslog
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@ -229,6 +229,30 @@ uint32_t *arm_syscall(uint32_t *regs)
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}
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break;
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/* R0=SYS_context_restore: Restore task context
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*
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* void up_fullcontextrestore(uint32_t *restoreregs) noreturn_function;
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*
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* At this point, the following values are saved in context:
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*
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* R0 = SYS_context_restore
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* R1 = restoreregs
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*/
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#ifdef CONFIG_BUILD_KERNEL
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case SYS_context_restore:
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{
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/* Replace 'regs' with the pointer to the register set in
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* regs[REG_R1]. On return from the system call, that register
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* set will determine the restored context.
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*/
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regs = (uint32_t *)regs[REG_R1];
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DEBUGASSERT(regs);
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}
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break;
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#endif
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/* R0=SYS_task_start: This a user task start
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*
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* void up_task_start(main_t taskentry, int argc, FAR char *argv[]) noreturn_function;
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@ -427,9 +451,9 @@ uint32_t *arm_syscall(uint32_t *regs)
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svcdbg("CPSR: %08x\n", regs[REG_CPSR]);
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#endif
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/* Return the last value of curent_regs. This supports context switchs
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* on return from the exception. That capability is not used here,
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* however.
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/* Return the last value of curent_regs. This supports context switches
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* on return from the exception. That capability is only used with the
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* SYS_context_switch system call.
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*/
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return regs;
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@ -101,7 +101,7 @@ static void sig_trampoline(void)
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" blx ip\n" /* Call the signal handler */
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" pop {r2}\n" /* Recover LR in R2 */
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" mov lr, r2\n" /* Restore LR */
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" mov r0, #4\n" /* SYS_signal_handler_return */
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" mov r0, #5\n" /* SYS_signal_handler_return */
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" svc #0x900001\n" /* Return from the signal handler */
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);
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}
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@ -60,9 +60,9 @@
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#ifdef CONFIG_BUILD_KERNEL
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# ifndef CONFIG_SYS_RESERVED
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# error "CONFIG_SYS_RESERVED must be defined to have the value 5"
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# elif CONFIG_SYS_RESERVED != 5
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# error "CONFIG_SYS_RESERVED must have the value 5"
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# error "CONFIG_SYS_RESERVED must be defined to have the value 6"
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# elif CONFIG_SYS_RESERVED != 6
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# error "CONFIG_SYS_RESERVED must have the value 6"
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# endif
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#else
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# ifndef CONFIG_SYS_RESERVED
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@ -83,35 +83,42 @@
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#ifdef CONFIG_BUILD_KERNEL
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/* SYS call 1:
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*
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* void up_fullcontextrestore(uint32_t *restoreregs) noreturn_function;
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*/
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#define SYS_context_restore (1)
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/* SYS call 2:
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*
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* void up_task_start(main_t taskentry, int argc, FAR char *argv[])
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* noreturn_function;
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*/
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#define SYS_task_start (1)
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#define SYS_task_start (2)
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/* SYS call 2:
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/* SYS call 3:
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*
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* void up_pthread_start(pthread_startroutine_t entrypt, pthread_addr_t arg)
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* noreturn_function
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*/
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#define SYS_pthread_start (2)
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#define SYS_pthread_start (3)
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/* SYS call 3:
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/* SYS call 4:
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*
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* void signal_handler(_sa_sigaction_t sighand, int signo, FAR siginfo_t *info,
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* FAR void *ucontext);
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*/
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#define SYS_signal_handler (3)
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#define SYS_signal_handler (4)
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/* SYS call 4:
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/* SYS call 5:
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*
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* void signal_handler_return(void);
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*/
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#define SYS_signal_handler_return (4)
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#define SYS_signal_handler_return (5)
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#endif /* CONFIG_BUILD_KERNEL */
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@ -455,7 +455,7 @@ CONFIG_USERMAIN_STACKSIZE=2048
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CONFIG_PTHREAD_STACK_MIN=256
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CONFIG_PTHREAD_STACK_DEFAULT=2048
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CONFIG_LIB_SYSCALL=y
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CONFIG_SYS_RESERVED=5
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CONFIG_SYS_RESERVED=6
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CONFIG_SYS_NNEST=2
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#
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@ -438,7 +438,7 @@ CONFIG_USERMAIN_STACKSIZE=2048
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CONFIG_PTHREAD_STACK_MIN=256
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CONFIG_PTHREAD_STACK_DEFAULT=2048
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CONFIG_LIB_SYSCALL=y
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CONFIG_SYS_RESERVED=5
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CONFIG_SYS_RESERVED=6
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CONFIG_SYS_NNEST=2
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#
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