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commit 190a2e306c199e3b30e54d9e7b3630c690f86df0 Author: Ville Juven <[email protected]> AuthorDate: Thu Oct 3 11:52:42 2024 +0300 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. --- arch/risc-v/include/irq.h | 3 + arch/risc-v/include/syscall.h | 26 ++------ arch/risc-v/src/common/riscv_exception_common.S | 36 ++++++++++ arch/risc-v/src/common/riscv_initialstate.c | 4 ++ arch/risc-v/src/common/riscv_internal.h | 4 ++ arch/risc-v/src/common/riscv_pthread_start.c | 24 +++++-- arch/risc-v/src/common/riscv_swint.c | 87 ------------------------- arch/risc-v/src/common/riscv_task_start.c | 30 +++++++-- 8 files changed, 98 insertions(+), 116 deletions(-) diff --git a/arch/risc-v/include/irq.h b/arch/risc-v/include/irq.h index cd2665cd88..40f6275fd9 100644 --- a/arch/risc-v/include/irq.h +++ b/arch/risc-v/include/irq.h @@ -612,6 +612,9 @@ struct xcptcontext /* Integer register save area */ uintreg_t *regs; +#ifndef CONFIG_BUILD_FLAT + uintreg_t *initregs; +#endif #ifdef CONFIG_LIB_SYSCALL /* User integer registers upon system call entry */ diff --git a/arch/risc-v/include/syscall.h b/arch/risc-v/include/syscall.h index 9d22006760..834b2848dd 100644 --- a/arch/risc-v/include/syscall.h +++ b/arch/risc-v/include/syscall.h @@ -50,7 +50,7 @@ */ #ifndef CONFIG_BUILD_FLAT -# define CONFIG_SYS_RESERVED 8 +# define CONFIG_SYS_RESERVED 6 #else # define CONFIG_SYS_RESERVED 4 #endif @@ -78,37 +78,21 @@ #define SYS_switch_context (2) #ifndef CONFIG_BUILD_FLAT -/* SYS call 4: - * - * void up_task_start(main_t taskentry, int argc, char *argv[]) - * noreturn_function; - */ -#define SYS_task_start (4) - -/* SYS call 5: - * - * void up_pthread_start(pthread_startroutine_t startup, - * pthread_startroutine_t entrypt, pthread_addr_t arg) - * noreturn_function - */ - -#define SYS_pthread_start (5) - -/* SYS call 6: +/* SYS call 4: * * void signal_handler(_sa_sigaction_t sighand, int signo, * siginfo_t *info, void *ucontext); */ -#define SYS_signal_handler (6) +#define SYS_signal_handler (4) -/* SYS call 7: +/* SYS call 5: * * void signal_handler_return(void); */ -#define SYS_signal_handler_return (7) +#define SYS_signal_handler_return (5) #endif /* !CONFIG_BUILD_FLAT */ /**************************************************************************** diff --git a/arch/risc-v/src/common/riscv_exception_common.S b/arch/risc-v/src/common/riscv_exception_common.S index 5035a01c7b..ec585f653a 100644 --- a/arch/risc-v/src/common/riscv_exception_common.S +++ b/arch/risc-v/src/common/riscv_exception_common.S @@ -273,6 +273,42 @@ return_from_exception: ERET +/**************************************************************************** + * Function: riscv_jump_to_user + * + * Description: + * Routine to jump to user space, called when a user process is started and + * the kernel is ready to give control to the user task in user space. + * + * riscv_jump_to_user(entry, a0, a1, a2, sp, regs) + * entry: process entry point + * a0: parameter 0 for process + * a1: parameter 1 for process + * a2: parameter 2 for process + * sp: user stack pointer + * regs: integer register save area to use + * + ****************************************************************************/ + + .section EXCEPTION_SECTION + .global riscv_jump_to_user + +riscv_jump_to_user: + + csrc CSR_STATUS, STATUS_IE + mv sp, a5 + REGSTORE a0, REG_EPC(sp) + REGSTORE a1, REG_A0(sp) + REGSTORE a2, REG_A1(sp) + REGSTORE a3, REG_A2(sp) + REGSTORE a4, REG_SP(sp) + csrr a0, CSR_STATUS + li a1, ~STATUS_PPP + and a0, a0, a1 + REGSTORE a0, REG_INT_CTX(sp) + mv a0, sp + tail return_from_exception + /***************************************************************************** * Name: g_intstackalloc and g_intstacktop ****************************************************************************/ diff --git a/arch/risc-v/src/common/riscv_initialstate.c b/arch/risc-v/src/common/riscv_initialstate.c index f787ed57b7..7eb4aebcad 100644 --- a/arch/risc-v/src/common/riscv_initialstate.c +++ b/arch/risc-v/src/common/riscv_initialstate.c @@ -169,4 +169,8 @@ void up_initial_state(struct tcb_s *tcb) #ifdef CONFIG_ARCH_RISCV_INTXCPT_EXTENSIONS riscv_initial_extctx_state(tcb); #endif + +#ifndef CONFIG_BUILD_FLAT + tcb->xcp.initregs = tcb->xcp.regs; +#endif } diff --git a/arch/risc-v/src/common/riscv_internal.h b/arch/risc-v/src/common/riscv_internal.h index d9165356a9..7878d762aa 100644 --- a/arch/risc-v/src/common/riscv_internal.h +++ b/arch/risc-v/src/common/riscv_internal.h @@ -434,6 +434,10 @@ uintptr_t riscv_mhartid(void); void *riscv_perform_syscall(uintreg_t *regs); #endif +void riscv_jump_to_user(uintptr_t entry, uintreg_t a0, uintreg_t a1, + uintreg_t a2, uintreg_t sp, + uintreg_t *regs) noreturn_function; + /* Context switching via system calls ***************************************/ /* SYS call 1: diff --git a/arch/risc-v/src/common/riscv_pthread_start.c b/arch/risc-v/src/common/riscv_pthread_start.c index 8dd295a1b8..4d3056efa0 100644 --- a/arch/risc-v/src/common/riscv_pthread_start.c +++ b/arch/risc-v/src/common/riscv_pthread_start.c @@ -31,6 +31,8 @@ #include "riscv_internal.h" +#include "sched/sched.h" + #if !defined(CONFIG_BUILD_FLAT) && defined(__KERNEL__) && \ !defined(CONFIG_DISABLE_PTHREAD) @@ -66,12 +68,26 @@ void up_pthread_start(pthread_trampoline_t startup, pthread_startroutine_t entrypt, pthread_addr_t arg) { - /* Let sys_call3() do all of the work */ + struct tcb_s *rtcb = this_task(); + uintptr_t sp; + +#ifdef CONFIG_ARCH_KERNEL_STACK + sp = (uintreg_t)rtcb->xcp.ustkptr; +#else + sp = (uintptr_t)rtcb->stack_base_ptr + rtcb->adj_stack_size; +#endif - sys_call3(SYS_pthread_start, (uintptr_t)startup, (uintptr_t)entrypt, - (uintptr_t)arg); + /* Set up to return to the user-space _start function in + * unprivileged mode. We need: + * + * A0 = entrypt + * A1 = arg + * EPC = startup + * M/SPP = user mode + */ - PANIC(); + riscv_jump_to_user((uintptr_t)startup, (uintreg_t)entrypt, (uintreg_t)arg, + 0, sp, rtcb->xcp.initregs); } #endif /* !CONFIG_BUILD_FLAT && __KERNEL__ && !CONFIG_DISABLE_PTHREAD */ diff --git a/arch/risc-v/src/common/riscv_swint.c b/arch/risc-v/src/common/riscv_swint.c index ce2a2ad154..ab6fc22428 100644 --- a/arch/risc-v/src/common/riscv_swint.c +++ b/arch/risc-v/src/common/riscv_swint.c @@ -212,93 +212,6 @@ int riscv_swint(int irq, void *context, void *arg) } break; - /* R0=SYS_task_start: This a user task start - * - * void up_task_start(main_t taskentry, int argc, - * char *argv[]) noreturn_function; - * - * At this point, the following values are saved in context: - * - * A0 = SYS_task_start - * A1 = taskentry - * A2 = argc - * A3 = argv - */ - -#ifndef CONFIG_BUILD_FLAT - case SYS_task_start: - { - /* Set up to return to the user-space task start-up function in - * unprivileged mode. - */ - -#ifdef CONFIG_ARCH_KERNEL_STACK - /* Set the user stack pointer as we are about to return to user */ - - struct tcb_s *tcb = this_task(); - regs[REG_SP] = (uintptr_t)tcb->xcp.ustkptr; - tcb->xcp.ustkptr = NULL; -#endif - -#if defined (CONFIG_BUILD_PROTECTED) - /* Use the nxtask_startup trampoline function */ - - regs[REG_EPC] = (uintptr_t)USERSPACE->task_startup; - regs[REG_A0] = regs[REG_A1]; /* Task entry */ - regs[REG_A1] = regs[REG_A2]; /* argc */ - regs[REG_A2] = regs[REG_A3]; /* argv */ -#else - /* Start the user task directly */ - - regs[REG_EPC] = (uintptr_t)regs[REG_A1]; - regs[REG_A0] = regs[REG_A2]; /* argc */ - regs[REG_A1] = regs[REG_A3]; /* argv */ -#endif - regs[REG_INT_CTX] &= ~STATUS_PPP; /* User mode */ - } - break; -#endif - - /* R0=SYS_pthread_start: This a user pthread start - * - * void up_pthread_start(pthread_startroutine_t entrypt, - * pthread_addr_t arg) noreturn_function; - * - * At this point, the following values are saved in context: - * - * A0 = SYS_pthread_start - * A1 = entrypt - * A2 = arg - */ - -#if !defined(CONFIG_BUILD_FLAT) && !defined(CONFIG_DISABLE_PTHREAD) - case SYS_pthread_start: - { - /* Set up to return to the user-space pthread start-up function in - * unprivileged mode. - */ - -#ifdef CONFIG_ARCH_KERNEL_STACK - /* Set the user stack pointer as we are about to return to user */ - - struct tcb_s *tcb = this_task(); - regs[REG_SP] = (uintptr_t)tcb->xcp.ustkptr; - tcb->xcp.ustkptr = NULL; -#endif - - regs[REG_EPC] = (uintptr_t)regs[REG_A1]; /* startup */ - - /* Change the parameter ordering to match the expectation of the - * user space pthread_startup: - */ - - regs[REG_A0] = regs[REG_A2]; /* pthread entry */ - regs[REG_A1] = regs[REG_A3]; /* arg */ - regs[REG_INT_CTX] &= ~STATUS_PPP; /* User mode */ - } - break; -#endif - /* R0=SYS_signal_handler: This a user signal handler callback * * void signal_handler(_sa_sigaction_t sighand, int signo, diff --git a/arch/risc-v/src/common/riscv_task_start.c b/arch/risc-v/src/common/riscv_task_start.c index d8cc966f8a..c664392f27 100644 --- a/arch/risc-v/src/common/riscv_task_start.c +++ b/arch/risc-v/src/common/riscv_task_start.c @@ -30,6 +30,8 @@ #include "riscv_internal.h" +#include "sched/sched.h" + #ifndef CONFIG_BUILD_FLAT /**************************************************************************** @@ -63,12 +65,32 @@ void up_task_start(main_t taskentry, int argc, char *argv[]) { - /* Let sys_call3() do all of the work */ + struct tcb_s *rtcb = this_task(); + uintptr_t sp; + +#ifdef CONFIG_ARCH_KERNEL_STACK + sp = (uintreg_t)rtcb->xcp.ustkptr; +#else + sp = (uintptr_t)rtcb->stack_base_ptr + rtcb->adj_stack_size; +#endif - sys_call3(SYS_task_start, (uintptr_t)taskentry, (uintptr_t)argc, - (uintptr_t)argv); + /* Set up to return to the user-space _start function in + * unprivileged mode. We need: + * + * A0 = argc + * A1 = argv + * EPC = taskentry + * M/SPP = user mode + */ - PANIC(); +#if defined(CONFIG_BUILD_PROTECTED) + riscv_jump_to_user((uintptr_t)USERSPACE->task_startup, + (uintptr_t)taskentry, (uintreg_t)argc, (uintreg_t)argv, + sp, rtcb->xcp.initregs); +#else + riscv_jump_to_user((uintptr_t)taskentry, (uintreg_t)argc, (uintreg_t)argv, + 0, sp, rtcb->xcp.initregs); +#endif } #endif /* !CONFIG_BUILD_FLAT */
