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https://github.com/apache/nuttx.git
synced 2026-05-23 14:49:22 +08:00
riscv/syscall: Simplify task/pthread_start logic
This removes 2 reserved system calls and replaces them with an ASM snippet. The result removes an unnecessary ecall from the process startup logic, as well as ensures the stacks are FULLY unwound when the user process starts. The logic is ported from ARM64.
This commit is contained in:
Ville Juven
Xiang Xiao
@@ -612,6 +612,9 @@ struct xcptcontext
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/* Integer register save area */
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uintreg_t *regs;
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#ifndef CONFIG_BUILD_FLAT
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uintreg_t *initregs;
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#endif
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#ifdef CONFIG_LIB_SYSCALL
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/* User integer registers upon system call entry */
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@@ -50,7 +50,7 @@
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*/
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#ifndef CONFIG_BUILD_FLAT
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# define CONFIG_SYS_RESERVED 8
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# define CONFIG_SYS_RESERVED 6
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#else
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# define CONFIG_SYS_RESERVED 4
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#endif
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@@ -78,37 +78,21 @@
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#define SYS_switch_context (2)
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#ifndef CONFIG_BUILD_FLAT
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/* SYS call 4:
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*
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* void up_task_start(main_t taskentry, int argc, char *argv[])
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* noreturn_function;
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*/
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#define SYS_task_start (4)
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/* SYS call 5:
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*
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* void up_pthread_start(pthread_startroutine_t startup,
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* 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 (5)
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/* SYS call 6:
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*
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* void signal_handler(_sa_sigaction_t sighand, int signo,
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* siginfo_t *info, void *ucontext);
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*/
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#define SYS_signal_handler (6)
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#define SYS_signal_handler (4)
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/* SYS call 7:
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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 (7)
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#define SYS_signal_handler_return (5)
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#endif /* !CONFIG_BUILD_FLAT */
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/****************************************************************************
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@@ -273,6 +273,42 @@ return_from_exception:
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ERET
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/****************************************************************************
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* Function: riscv_jump_to_user
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*
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* Description:
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* Routine to jump to user space, called when a user process is started and
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* the kernel is ready to give control to the user task in user space.
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*
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* riscv_jump_to_user(entry, a0, a1, a2, sp, regs)
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* entry: process entry point
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* a0: parameter 0 for process
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* a1: parameter 1 for process
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* a2: parameter 2 for process
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* sp: user stack pointer
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* regs: integer register save area to use
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*
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****************************************************************************/
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.section EXCEPTION_SECTION
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.global riscv_jump_to_user
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riscv_jump_to_user:
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csrc CSR_STATUS, STATUS_IE
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mv sp, a5
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REGSTORE a0, REG_EPC(sp)
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REGSTORE a1, REG_A0(sp)
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REGSTORE a2, REG_A1(sp)
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REGSTORE a3, REG_A2(sp)
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REGSTORE a4, REG_SP(sp)
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csrr a0, CSR_STATUS
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li a1, ~STATUS_PPP
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and a0, a0, a1
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REGSTORE a0, REG_INT_CTX(sp)
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mv a0, sp
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tail return_from_exception
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/*****************************************************************************
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* Name: g_intstackalloc and g_intstacktop
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****************************************************************************/
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@@ -169,4 +169,8 @@ void up_initial_state(struct tcb_s *tcb)
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#ifdef CONFIG_ARCH_RISCV_INTXCPT_EXTENSIONS
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riscv_initial_extctx_state(tcb);
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#endif
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#ifndef CONFIG_BUILD_FLAT
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tcb->xcp.initregs = tcb->xcp.regs;
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#endif
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}
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@@ -434,6 +434,10 @@ uintptr_t riscv_mhartid(void);
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void *riscv_perform_syscall(uintreg_t *regs);
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#endif
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void riscv_jump_to_user(uintptr_t entry, uintreg_t a0, uintreg_t a1,
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uintreg_t a2, uintreg_t sp,
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uintreg_t *regs) noreturn_function;
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/* Context switching via system calls ***************************************/
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/* SYS call 1:
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@@ -31,6 +31,8 @@
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#include "riscv_internal.h"
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#include "sched/sched.h"
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#if !defined(CONFIG_BUILD_FLAT) && defined(__KERNEL__) && \
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!defined(CONFIG_DISABLE_PTHREAD)
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@@ -66,12 +68,26 @@
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void up_pthread_start(pthread_trampoline_t startup,
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pthread_startroutine_t entrypt, pthread_addr_t arg)
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{
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/* Let sys_call3() do all of the work */
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struct tcb_s *rtcb = this_task();
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uintptr_t sp;
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sys_call3(SYS_pthread_start, (uintptr_t)startup, (uintptr_t)entrypt,
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(uintptr_t)arg);
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#ifdef CONFIG_ARCH_KERNEL_STACK
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sp = (uintreg_t)rtcb->xcp.ustkptr;
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#else
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sp = (uintptr_t)rtcb->stack_base_ptr + rtcb->adj_stack_size;
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#endif
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PANIC();
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/* Set up to return to the user-space _start function in
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* unprivileged mode. We need:
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*
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* A0 = entrypt
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* A1 = arg
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* EPC = startup
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* M/SPP = user mode
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*/
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riscv_jump_to_user((uintptr_t)startup, (uintreg_t)entrypt, (uintreg_t)arg,
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0, sp, rtcb->xcp.initregs);
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}
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#endif /* !CONFIG_BUILD_FLAT && __KERNEL__ && !CONFIG_DISABLE_PTHREAD */
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@@ -212,93 +212,6 @@ int riscv_swint(int irq, void *context, void *arg)
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}
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break;
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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,
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* char *argv[]) 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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* A0 = SYS_task_start
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* A1 = taskentry
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* A2 = argc
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* A3 = argv
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*/
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#ifndef CONFIG_BUILD_FLAT
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case SYS_task_start:
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{
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/* Set up to return to the user-space task start-up function in
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* unprivileged mode.
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*/
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#ifdef CONFIG_ARCH_KERNEL_STACK
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/* Set the user stack pointer as we are about to return to user */
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struct tcb_s *tcb = this_task();
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regs[REG_SP] = (uintptr_t)tcb->xcp.ustkptr;
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tcb->xcp.ustkptr = NULL;
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#endif
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#if defined (CONFIG_BUILD_PROTECTED)
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/* Use the nxtask_startup trampoline function */
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regs[REG_EPC] = (uintptr_t)USERSPACE->task_startup;
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regs[REG_A0] = regs[REG_A1]; /* Task entry */
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regs[REG_A1] = regs[REG_A2]; /* argc */
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regs[REG_A2] = regs[REG_A3]; /* argv */
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#else
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/* Start the user task directly */
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regs[REG_EPC] = (uintptr_t)regs[REG_A1];
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regs[REG_A0] = regs[REG_A2]; /* argc */
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regs[REG_A1] = regs[REG_A3]; /* argv */
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#endif
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regs[REG_INT_CTX] &= ~STATUS_PPP; /* User mode */
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}
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break;
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#endif
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/* R0=SYS_pthread_start: This a user pthread start
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*
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* void up_pthread_start(pthread_startroutine_t entrypt,
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* pthread_addr_t arg) 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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* A0 = SYS_pthread_start
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* A1 = entrypt
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* A2 = arg
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*/
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#if !defined(CONFIG_BUILD_FLAT) && !defined(CONFIG_DISABLE_PTHREAD)
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case SYS_pthread_start:
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{
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/* Set up to return to the user-space pthread start-up function in
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* unprivileged mode.
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*/
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#ifdef CONFIG_ARCH_KERNEL_STACK
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/* Set the user stack pointer as we are about to return to user */
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struct tcb_s *tcb = this_task();
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regs[REG_SP] = (uintptr_t)tcb->xcp.ustkptr;
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tcb->xcp.ustkptr = NULL;
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#endif
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regs[REG_EPC] = (uintptr_t)regs[REG_A1]; /* startup */
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/* Change the parameter ordering to match the expectation of the
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* user space pthread_startup:
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*/
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regs[REG_A0] = regs[REG_A2]; /* pthread entry */
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regs[REG_A1] = regs[REG_A3]; /* arg */
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regs[REG_INT_CTX] &= ~STATUS_PPP; /* User mode */
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}
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break;
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#endif
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/* R0=SYS_signal_handler: This a user signal handler callback
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*
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* void signal_handler(_sa_sigaction_t sighand, int signo,
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@@ -30,6 +30,8 @@
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#include "riscv_internal.h"
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#include "sched/sched.h"
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#ifndef CONFIG_BUILD_FLAT
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/****************************************************************************
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@@ -63,12 +65,32 @@
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void up_task_start(main_t taskentry, int argc, char *argv[])
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{
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/* Let sys_call3() do all of the work */
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struct tcb_s *rtcb = this_task();
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uintptr_t sp;
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sys_call3(SYS_task_start, (uintptr_t)taskentry, (uintptr_t)argc,
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(uintptr_t)argv);
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#ifdef CONFIG_ARCH_KERNEL_STACK
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sp = (uintreg_t)rtcb->xcp.ustkptr;
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#else
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sp = (uintptr_t)rtcb->stack_base_ptr + rtcb->adj_stack_size;
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#endif
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PANIC();
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/* Set up to return to the user-space _start function in
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* unprivileged mode. We need:
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*
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* A0 = argc
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* A1 = argv
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* EPC = taskentry
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* M/SPP = user mode
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*/
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#if defined(CONFIG_BUILD_PROTECTED)
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riscv_jump_to_user((uintptr_t)USERSPACE->task_startup,
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(uintptr_t)taskentry, (uintreg_t)argc, (uintreg_t)argv,
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sp, rtcb->xcp.initregs);
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#else
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riscv_jump_to_user((uintptr_t)taskentry, (uintreg_t)argc, (uintreg_t)argv,
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0, sp, rtcb->xcp.initregs);
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#endif
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}
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#endif /* !CONFIG_BUILD_FLAT */
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