diff options
Diffstat (limited to 'arch/riscv/kernel/entry.S')
| -rw-r--r-- | arch/riscv/kernel/entry.S | 132 |
1 files changed, 98 insertions, 34 deletions
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index da7aa88113c2..a1349ca64669 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -26,14 +26,14 @@ /* * If coming from userspace, preserve the user thread pointer and load - * the kernel thread pointer. If we came from the kernel, sscratch - * will contain 0, and we should continue on the current TP. + * the kernel thread pointer. If we came from the kernel, the scratch + * register will contain 0, and we should continue on the current TP. */ - csrrw tp, CSR_SSCRATCH, tp + csrrw tp, CSR_SCRATCH, tp bnez tp, _save_context _restore_kernel_tpsp: - csrr tp, CSR_SSCRATCH + csrr tp, CSR_SCRATCH REG_S sp, TASK_TI_KERNEL_SP(tp) _save_context: REG_S sp, TASK_TI_USER_SP(tp) @@ -79,16 +79,16 @@ _save_context: li t0, SR_SUM | SR_FS REG_L s0, TASK_TI_USER_SP(tp) - csrrc s1, CSR_SSTATUS, t0 - csrr s2, CSR_SEPC - csrr s3, CSR_STVAL - csrr s4, CSR_SCAUSE - csrr s5, CSR_SSCRATCH + csrrc s1, CSR_STATUS, t0 + csrr s2, CSR_EPC + csrr s3, CSR_TVAL + csrr s4, CSR_CAUSE + csrr s5, CSR_SCRATCH REG_S s0, PT_SP(sp) - REG_S s1, PT_SSTATUS(sp) - REG_S s2, PT_SEPC(sp) - REG_S s3, PT_SBADADDR(sp) - REG_S s4, PT_SCAUSE(sp) + REG_S s1, PT_STATUS(sp) + REG_S s2, PT_EPC(sp) + REG_S s3, PT_BADADDR(sp) + REG_S s4, PT_CAUSE(sp) REG_S s5, PT_TP(sp) .endm @@ -97,10 +97,29 @@ _save_context: * registers from the stack. */ .macro RESTORE_ALL - REG_L a0, PT_SSTATUS(sp) - REG_L a2, PT_SEPC(sp) - csrw CSR_SSTATUS, a0 - csrw CSR_SEPC, a2 + REG_L a0, PT_STATUS(sp) + /* + * The current load reservation is effectively part of the processor's + * state, in the sense that load reservations cannot be shared between + * different hart contexts. We can't actually save and restore a load + * reservation, so instead here we clear any existing reservation -- + * it's always legal for implementations to clear load reservations at + * any point (as long as the forward progress guarantee is kept, but + * we'll ignore that here). + * + * Dangling load reservations can be the result of taking a trap in the + * middle of an LR/SC sequence, but can also be the result of a taken + * forward branch around an SC -- which is how we implement CAS. As a + * result we need to clear reservations between the last CAS and the + * jump back to the new context. While it is unlikely the store + * completes, implementations are allowed to expand reservations to be + * arbitrarily large. + */ + REG_L a2, PT_EPC(sp) + REG_SC x0, a2, PT_EPC(sp) + + csrw CSR_STATUS, a0 + csrw CSR_EPC, a2 REG_L x1, PT_RA(sp) REG_L x3, PT_GP(sp) @@ -144,10 +163,10 @@ ENTRY(handle_exception) SAVE_ALL /* - * Set sscratch register to 0, so that if a recursive exception + * Set the scratch register to 0, so that if a recursive exception * occurs, the exception vector knows it came from the kernel */ - csrw CSR_SSCRATCH, x0 + csrw CSR_SCRATCH, x0 /* Load the global pointer */ .option push @@ -166,11 +185,13 @@ ENTRY(handle_exception) move a0, sp /* pt_regs */ tail do_IRQ 1: - /* Exceptions run with interrupts enabled or disabled - depending on the state of sstatus.SR_SPIE */ - andi t0, s1, SR_SPIE + /* + * Exceptions run with interrupts enabled or disabled depending on the + * state of SR_PIE in m/sstatus. + */ + andi t0, s1, SR_PIE beqz t0, 1f - csrs CSR_SSTATUS, SR_SIE + csrs CSR_STATUS, SR_IE 1: /* Handle syscalls */ @@ -198,7 +219,7 @@ handle_syscall: * scall instruction on sret */ addi s2, s2, 0x4 - REG_S s2, PT_SEPC(sp) + REG_S s2, PT_EPC(sp) /* Trace syscalls, but only if requested by the user. */ REG_L t0, TASK_TI_FLAGS(tp) andi t0, t0, _TIF_SYSCALL_WORK @@ -207,8 +228,25 @@ check_syscall_nr: /* Check to make sure we don't jump to a bogus syscall number. */ li t0, __NR_syscalls la s0, sys_ni_syscall - /* Syscall number held in a7 */ - bgeu a7, t0, 1f + /* + * The tracer can change syscall number to valid/invalid value. + * We use syscall_set_nr helper in syscall_trace_enter thus we + * cannot trust the current value in a7 and have to reload from + * the current task pt_regs. + */ + REG_L a7, PT_A7(sp) + /* + * Syscall number held in a7. + * If syscall number is above allowed value, redirect to ni_syscall. + */ + bge a7, t0, 1f + /* + * Check if syscall is rejected by tracer or seccomp, i.e., a7 == -1. + * If yes, we pretend it was executed. + */ + li t1, -1 + beq a7, t1, ret_from_syscall_rejected + /* Call syscall */ la s0, sys_call_table slli t0, a7, RISCV_LGPTR add s0, s0, t0 @@ -219,15 +257,27 @@ check_syscall_nr: ret_from_syscall: /* Set user a0 to kernel a0 */ REG_S a0, PT_A0(sp) + /* + * We didn't execute the actual syscall. + * Seccomp already set return value for the current task pt_regs. + * (If it was configured with SECCOMP_RET_ERRNO/TRACE) + */ +ret_from_syscall_rejected: /* Trace syscalls, but only if requested by the user. */ REG_L t0, TASK_TI_FLAGS(tp) andi t0, t0, _TIF_SYSCALL_WORK bnez t0, handle_syscall_trace_exit ret_from_exception: - REG_L s0, PT_SSTATUS(sp) - csrc CSR_SSTATUS, SR_SIE + REG_L s0, PT_STATUS(sp) + csrc CSR_STATUS, SR_IE +#ifdef CONFIG_RISCV_M_MODE + /* the MPP value is too large to be used as an immediate arg for addi */ + li t0, SR_MPP + and s0, s0, t0 +#else andi s0, s0, SR_SPP +#endif bnez s0, resume_kernel resume_userspace: @@ -241,25 +291,28 @@ resume_userspace: REG_S s0, TASK_TI_KERNEL_SP(tp) /* - * Save TP into sscratch, so we can find the kernel data structures - * again. + * Save TP into the scratch register , so we can find the kernel data + * structures again. */ - csrw CSR_SSCRATCH, tp + csrw CSR_SCRATCH, tp restore_all: RESTORE_ALL +#ifdef CONFIG_RISCV_M_MODE + mret +#else sret +#endif #if IS_ENABLED(CONFIG_PREEMPT) resume_kernel: REG_L s0, TASK_TI_PREEMPT_COUNT(tp) bnez s0, restore_all -need_resched: REG_L s0, TASK_TI_FLAGS(tp) andi s0, s0, _TIF_NEED_RESCHED beqz s0, restore_all call preempt_schedule_irq - j need_resched + j restore_all #endif work_pending: @@ -269,7 +322,7 @@ work_pending: bnez s1, work_resched work_notifysig: /* Handle pending signals and notify-resume requests */ - csrs CSR_SSTATUS, SR_SIE /* Enable interrupts for do_notify_resume() */ + csrs CSR_STATUS, SR_IE /* Enable interrupts for do_notify_resume() */ move a0, sp /* pt_regs */ move a1, s0 /* current_thread_info->flags */ tail do_notify_resume @@ -368,6 +421,10 @@ ENTRY(__switch_to) ret ENDPROC(__switch_to) +#ifndef CONFIG_MMU +#define do_page_fault do_trap_unknown +#endif + .section ".rodata" /* Exception vector table */ ENTRY(excp_vect_table) @@ -389,3 +446,10 @@ ENTRY(excp_vect_table) RISCV_PTR do_page_fault /* store page fault */ excp_vect_table_end: END(excp_vect_table) + +#ifndef CONFIG_MMU +ENTRY(__user_rt_sigreturn) + li a7, __NR_rt_sigreturn + scall +END(__user_rt_sigreturn) +#endif |