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Diffstat (limited to 'arch/arm64/kernel/sdei.c')
| -rw-r--r-- | arch/arm64/kernel/sdei.c | 242 |
1 files changed, 242 insertions, 0 deletions
diff --git a/arch/arm64/kernel/sdei.c b/arch/arm64/kernel/sdei.c new file mode 100644 index 000000000..0083f5afa --- /dev/null +++ b/arch/arm64/kernel/sdei.c @@ -0,0 +1,242 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (C) 2017 Arm Ltd. +#define pr_fmt(fmt) "sdei: " fmt + +#include <linux/arm-smccc.h> +#include <linux/arm_sdei.h> +#include <linux/hardirq.h> +#include <linux/irqflags.h> +#include <linux/sched/task_stack.h> +#include <linux/uaccess.h> + +#include <asm/alternative.h> +#include <asm/exception.h> +#include <asm/kprobes.h> +#include <asm/mmu.h> +#include <asm/ptrace.h> +#include <asm/sections.h> +#include <asm/stacktrace.h> +#include <asm/sysreg.h> +#include <asm/vmap_stack.h> + +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 + +DEFINE_PER_CPU(struct sdei_registered_event *, sdei_active_normal_event); +DEFINE_PER_CPU(struct sdei_registered_event *, sdei_active_critical_event); + +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; + + return on_stack(sp, low, high, STACK_TYPE_SDEI_NORMAL, info); +} + +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; + + return on_stack(sp, low, high, STACK_TYPE_SDEI_CRITICAL, info); +} + +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 == SMCCC_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 force_uaccess_begin() 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 noinstr unsigned long +__sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg) +{ + unsigned long ret; + + arm64_enter_nmi(regs); + + ret = _sdei_handler(regs, arg); + + arm64_exit_nmi(regs); + + return ret; +} |