1 // SPDX-License-Identifier: GPL-2.0 2 // Copyright (C) 2017 Arm Ltd. 3 #define pr_fmt(fmt) "sdei: " fmt 4 5 #include <linux/arm-smccc.h> 6 #include <linux/arm_sdei.h> 7 #include <linux/hardirq.h> 8 #include <linux/irqflags.h> 9 #include <linux/sched/task_stack.h> 10 #include <linux/uaccess.h> 11 12 #include <asm/alternative.h> 13 #include <asm/exception.h> 14 #include <asm/kprobes.h> 15 #include <asm/mmu.h> 16 #include <asm/ptrace.h> 17 #include <asm/sections.h> 18 #include <asm/stacktrace.h> 19 #include <asm/sysreg.h> 20 #include <asm/vmap_stack.h> 21 22 unsigned long sdei_exit_mode; 23 24 /* 25 * VMAP'd stacks checking for stack overflow on exception using sp as a scratch 26 * register, meaning SDEI has to switch to its own stack. We need two stacks as 27 * a critical event may interrupt a normal event that has just taken a 28 * synchronous exception, and is using sp as scratch register. For a critical 29 * event interrupting a normal event, we can't reliably tell if we were on the 30 * sdei stack. 31 * For now, we allocate stacks when the driver is probed. 32 */ 33 DECLARE_PER_CPU(unsigned long *, sdei_stack_normal_ptr); 34 DECLARE_PER_CPU(unsigned long *, sdei_stack_critical_ptr); 35 36 #ifdef CONFIG_VMAP_STACK 37 DEFINE_PER_CPU(unsigned long *, sdei_stack_normal_ptr); 38 DEFINE_PER_CPU(unsigned long *, sdei_stack_critical_ptr); 39 #endif 40 41 static void _free_sdei_stack(unsigned long * __percpu *ptr, int cpu) 42 { 43 unsigned long *p; 44 45 p = per_cpu(*ptr, cpu); 46 if (p) { 47 per_cpu(*ptr, cpu) = NULL; 48 vfree(p); 49 } 50 } 51 52 static void free_sdei_stacks(void) 53 { 54 int cpu; 55 56 for_each_possible_cpu(cpu) { 57 _free_sdei_stack(&sdei_stack_normal_ptr, cpu); 58 _free_sdei_stack(&sdei_stack_critical_ptr, cpu); 59 } 60 } 61 62 static int _init_sdei_stack(unsigned long * __percpu *ptr, int cpu) 63 { 64 unsigned long *p; 65 66 p = arch_alloc_vmap_stack(SDEI_STACK_SIZE, cpu_to_node(cpu)); 67 if (!p) 68 return -ENOMEM; 69 per_cpu(*ptr, cpu) = p; 70 71 return 0; 72 } 73 74 static int init_sdei_stacks(void) 75 { 76 int cpu; 77 int err = 0; 78 79 for_each_possible_cpu(cpu) { 80 err = _init_sdei_stack(&sdei_stack_normal_ptr, cpu); 81 if (err) 82 break; 83 err = _init_sdei_stack(&sdei_stack_critical_ptr, cpu); 84 if (err) 85 break; 86 } 87 88 if (err) 89 free_sdei_stacks(); 90 91 return err; 92 } 93 94 static bool on_sdei_normal_stack(unsigned long sp, struct stack_info *info) 95 { 96 unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_normal_ptr); 97 unsigned long high = low + SDEI_STACK_SIZE; 98 99 return on_stack(sp, low, high, STACK_TYPE_SDEI_NORMAL, info); 100 } 101 102 static bool on_sdei_critical_stack(unsigned long sp, struct stack_info *info) 103 { 104 unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_critical_ptr); 105 unsigned long high = low + SDEI_STACK_SIZE; 106 107 return on_stack(sp, low, high, STACK_TYPE_SDEI_CRITICAL, info); 108 } 109 110 bool _on_sdei_stack(unsigned long sp, struct stack_info *info) 111 { 112 if (!IS_ENABLED(CONFIG_VMAP_STACK)) 113 return false; 114 115 if (on_sdei_critical_stack(sp, info)) 116 return true; 117 118 if (on_sdei_normal_stack(sp, info)) 119 return true; 120 121 return false; 122 } 123 124 unsigned long sdei_arch_get_entry_point(int conduit) 125 { 126 /* 127 * SDEI works between adjacent exception levels. If we booted at EL1 we 128 * assume a hypervisor is marshalling events. If we booted at EL2 and 129 * dropped to EL1 because we don't support VHE, then we can't support 130 * SDEI. 131 */ 132 if (is_hyp_mode_available() && !is_kernel_in_hyp_mode()) { 133 pr_err("Not supported on this hardware/boot configuration\n"); 134 return 0; 135 } 136 137 if (IS_ENABLED(CONFIG_VMAP_STACK)) { 138 if (init_sdei_stacks()) 139 return 0; 140 } 141 142 sdei_exit_mode = (conduit == SMCCC_CONDUIT_HVC) ? SDEI_EXIT_HVC : SDEI_EXIT_SMC; 143 144 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 145 if (arm64_kernel_unmapped_at_el0()) { 146 unsigned long offset; 147 148 offset = (unsigned long)__sdei_asm_entry_trampoline - 149 (unsigned long)__entry_tramp_text_start; 150 return TRAMP_VALIAS + offset; 151 } else 152 #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ 153 return (unsigned long)__sdei_asm_handler; 154 155 } 156 157 /* 158 * __sdei_handler() returns one of: 159 * SDEI_EV_HANDLED - success, return to the interrupted context. 160 * SDEI_EV_FAILED - failure, return this error code to firmare. 161 * virtual-address - success, return to this address. 162 */ 163 static __kprobes unsigned long _sdei_handler(struct pt_regs *regs, 164 struct sdei_registered_event *arg) 165 { 166 u32 mode; 167 int i, err = 0; 168 int clobbered_registers = 4; 169 u64 elr = read_sysreg(elr_el1); 170 u32 kernel_mode = read_sysreg(CurrentEL) | 1; /* +SPSel */ 171 unsigned long vbar = read_sysreg(vbar_el1); 172 173 if (arm64_kernel_unmapped_at_el0()) 174 clobbered_registers++; 175 176 /* Retrieve the missing registers values */ 177 for (i = 0; i < clobbered_registers; i++) { 178 /* from within the handler, this call always succeeds */ 179 sdei_api_event_context(i, ®s->regs[i]); 180 } 181 182 /* 183 * We didn't take an exception to get here, set PAN. UAO will be cleared 184 * by sdei_event_handler()s force_uaccess_begin() call. 185 */ 186 __uaccess_enable_hw_pan(); 187 188 err = sdei_event_handler(regs, arg); 189 if (err) 190 return SDEI_EV_FAILED; 191 192 if (elr != read_sysreg(elr_el1)) { 193 /* 194 * We took a synchronous exception from the SDEI handler. 195 * This could deadlock, and if you interrupt KVM it will 196 * hyp-panic instead. 197 */ 198 pr_warn("unsafe: exception during handler\n"); 199 } 200 201 mode = regs->pstate & (PSR_MODE32_BIT | PSR_MODE_MASK); 202 203 /* 204 * If we interrupted the kernel with interrupts masked, we always go 205 * back to wherever we came from. 206 */ 207 if (mode == kernel_mode && !interrupts_enabled(regs)) 208 return SDEI_EV_HANDLED; 209 210 /* 211 * Otherwise, we pretend this was an IRQ. This lets user space tasks 212 * receive signals before we return to them, and KVM to invoke it's 213 * world switch to do the same. 214 * 215 * See DDI0487B.a Table D1-7 'Vector offsets from vector table base 216 * address'. 217 */ 218 if (mode == kernel_mode) 219 return vbar + 0x280; 220 else if (mode & PSR_MODE32_BIT) 221 return vbar + 0x680; 222 223 return vbar + 0x480; 224 } 225 226 227 asmlinkage noinstr unsigned long 228 __sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg) 229 { 230 unsigned long ret; 231 232 arm64_enter_nmi(regs); 233 234 ret = _sdei_handler(regs, arg); 235 236 arm64_exit_nmi(regs); 237 238 return ret; 239 } 240