// SPDX-License-Identifier: GPL-2.0 // Copyright (C) 2017 Arm Ltd. #define pr_fmt(fmt) "sdei: " fmt #include #include #include #include #include #include #include #include #include #include #include #include #include unsigned long sdei_exit_mode; /* * VMAP'd stacks checking for stack overflow on exception using sp as a scratch * register, meaning SDEI has to switch to its own stack. We need two stacks as * a critical event may interrupt a normal event that has just taken a * synchronous exception, and is using sp as scratch register. For a critical * event interrupting a normal event, we can't reliably tell if we were on the * sdei stack. * For now, we allocate stacks when the driver is probed. */ DECLARE_PER_CPU(unsigned long *, sdei_stack_normal_ptr); DECLARE_PER_CPU(unsigned long *, sdei_stack_critical_ptr); #ifdef CONFIG_VMAP_STACK DEFINE_PER_CPU(unsigned long *, sdei_stack_normal_ptr); DEFINE_PER_CPU(unsigned long *, sdei_stack_critical_ptr); #endif static void _free_sdei_stack(unsigned long * __percpu *ptr, int cpu) { unsigned long *p; p = per_cpu(*ptr, cpu); if (p) { per_cpu(*ptr, cpu) = NULL; vfree(p); } } static void free_sdei_stacks(void) { int cpu; for_each_possible_cpu(cpu) { _free_sdei_stack(&sdei_stack_normal_ptr, cpu); _free_sdei_stack(&sdei_stack_critical_ptr, cpu); } } static int _init_sdei_stack(unsigned long * __percpu *ptr, int cpu) { unsigned long *p; p = arch_alloc_vmap_stack(SDEI_STACK_SIZE, cpu_to_node(cpu)); if (!p) return -ENOMEM; per_cpu(*ptr, cpu) = p; return 0; } static int init_sdei_stacks(void) { int cpu; int err = 0; for_each_possible_cpu(cpu) { err = _init_sdei_stack(&sdei_stack_normal_ptr, cpu); if (err) break; err = _init_sdei_stack(&sdei_stack_critical_ptr, cpu); if (err) break; } if (err) free_sdei_stacks(); return err; } static bool on_sdei_normal_stack(unsigned long sp, struct stack_info *info) { unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_normal_ptr); unsigned long high = low + SDEI_STACK_SIZE; if (!low) return false; if (sp < low || sp >= high) return false; if (info) { info->low = low; info->high = high; info->type = STACK_TYPE_SDEI_NORMAL; } return true; } static bool on_sdei_critical_stack(unsigned long sp, struct stack_info *info) { unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_critical_ptr); unsigned long high = low + SDEI_STACK_SIZE; if (!low) return false; if (sp < low || sp >= high) return false; if (info) { info->low = low; info->high = high; info->type = STACK_TYPE_SDEI_CRITICAL; } return true; } bool _on_sdei_stack(unsigned long sp, struct stack_info *info) { if (!IS_ENABLED(CONFIG_VMAP_STACK)) return false; if (on_sdei_critical_stack(sp, info)) return true; if (on_sdei_normal_stack(sp, info)) return true; return false; } unsigned long sdei_arch_get_entry_point(int conduit) { /* * SDEI works between adjacent exception levels. If we booted at EL1 we * assume a hypervisor is marshalling events. If we booted at EL2 and * dropped to EL1 because we don't support VHE, then we can't support * SDEI. */ if (is_hyp_mode_available() && !is_kernel_in_hyp_mode()) { pr_err("Not supported on this hardware/boot configuration\n"); return 0; } if (IS_ENABLED(CONFIG_VMAP_STACK)) { if (init_sdei_stacks()) return 0; } sdei_exit_mode = (conduit == CONDUIT_HVC) ? SDEI_EXIT_HVC : SDEI_EXIT_SMC; #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 if (arm64_kernel_unmapped_at_el0()) { unsigned long offset; offset = (unsigned long)__sdei_asm_entry_trampoline - (unsigned long)__entry_tramp_text_start; return TRAMP_VALIAS + offset; } else #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ return (unsigned long)__sdei_asm_handler; } /* * __sdei_handler() returns one of: * SDEI_EV_HANDLED - success, return to the interrupted context. * SDEI_EV_FAILED - failure, return this error code to firmare. * virtual-address - success, return to this address. */ static __kprobes unsigned long _sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg) { u32 mode; int i, err = 0; int clobbered_registers = 4; u64 elr = read_sysreg(elr_el1); u32 kernel_mode = read_sysreg(CurrentEL) | 1; /* +SPSel */ unsigned long vbar = read_sysreg(vbar_el1); if (arm64_kernel_unmapped_at_el0()) clobbered_registers++; /* Retrieve the missing registers values */ for (i = 0; i < clobbered_registers; i++) { /* from within the handler, this call always succeeds */ sdei_api_event_context(i, ®s->regs[i]); } /* * We didn't take an exception to get here, set PAN. UAO will be cleared * by sdei_event_handler()s set_fs(USER_DS) call. */ __uaccess_enable_hw_pan(); err = sdei_event_handler(regs, arg); if (err) return SDEI_EV_FAILED; if (elr != read_sysreg(elr_el1)) { /* * We took a synchronous exception from the SDEI handler. * This could deadlock, and if you interrupt KVM it will * hyp-panic instead. */ pr_warn("unsafe: exception during handler\n"); } mode = regs->pstate & (PSR_MODE32_BIT | PSR_MODE_MASK); /* * If we interrupted the kernel with interrupts masked, we always go * back to wherever we came from. */ if (mode == kernel_mode && !interrupts_enabled(regs)) return SDEI_EV_HANDLED; /* * Otherwise, we pretend this was an IRQ. This lets user space tasks * receive signals before we return to them, and KVM to invoke it's * world switch to do the same. * * See DDI0487B.a Table D1-7 'Vector offsets from vector table base * address'. */ if (mode == kernel_mode) return vbar + 0x280; else if (mode & PSR_MODE32_BIT) return vbar + 0x680; return vbar + 0x480; } asmlinkage __kprobes notrace unsigned long __sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg) { unsigned long ret; bool do_nmi_exit = false; /* * nmi_enter() deals with printk() re-entrance and use of RCU when * RCU believed this CPU was idle. Because critical events can * interrupt normal events, we may already be in_nmi(). */ if (!in_nmi()) { nmi_enter(); do_nmi_exit = true; } ret = _sdei_handler(regs, arg); if (do_nmi_exit) nmi_exit(); return ret; }