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/scs.h> 11 #include <linux/uaccess.h> 12 13 #include <asm/alternative.h> 14 #include <asm/exception.h> 15 #include <asm/kprobes.h> 16 #include <asm/mmu.h> 17 #include <asm/ptrace.h> 18 #include <asm/sections.h> 19 #include <asm/stacktrace.h> 20 #include <asm/sysreg.h> 21 #include <asm/vmap_stack.h> 22 23 unsigned long sdei_exit_mode; 24 25 /* 26 * VMAP'd stacks checking for stack overflow on exception using sp as a scratch 27 * register, meaning SDEI has to switch to its own stack. We need two stacks as 28 * a critical event may interrupt a normal event that has just taken a 29 * synchronous exception, and is using sp as scratch register. For a critical 30 * event interrupting a normal event, we can't reliably tell if we were on the 31 * sdei stack. 32 * For now, we allocate stacks when the driver is probed. 33 */ 34 DECLARE_PER_CPU(unsigned long *, sdei_stack_normal_ptr); 35 DECLARE_PER_CPU(unsigned long *, sdei_stack_critical_ptr); 36 37 #ifdef CONFIG_VMAP_STACK 38 DEFINE_PER_CPU(unsigned long *, sdei_stack_normal_ptr); 39 DEFINE_PER_CPU(unsigned long *, sdei_stack_critical_ptr); 40 #endif 41 42 DECLARE_PER_CPU(unsigned long *, sdei_shadow_call_stack_normal_ptr); 43 DECLARE_PER_CPU(unsigned long *, sdei_shadow_call_stack_critical_ptr); 44 45 #ifdef CONFIG_SHADOW_CALL_STACK 46 DEFINE_PER_CPU(unsigned long *, sdei_shadow_call_stack_normal_ptr); 47 DEFINE_PER_CPU(unsigned long *, sdei_shadow_call_stack_critical_ptr); 48 #endif 49 50 static void _free_sdei_stack(unsigned long * __percpu *ptr, int cpu) 51 { 52 unsigned long *p; 53 54 p = per_cpu(*ptr, cpu); 55 if (p) { 56 per_cpu(*ptr, cpu) = NULL; 57 vfree(p); 58 } 59 } 60 61 static void free_sdei_stacks(void) 62 { 63 int cpu; 64 65 if (!IS_ENABLED(CONFIG_VMAP_STACK)) 66 return; 67 68 for_each_possible_cpu(cpu) { 69 _free_sdei_stack(&sdei_stack_normal_ptr, cpu); 70 _free_sdei_stack(&sdei_stack_critical_ptr, cpu); 71 } 72 } 73 74 static int _init_sdei_stack(unsigned long * __percpu *ptr, int cpu) 75 { 76 unsigned long *p; 77 78 p = arch_alloc_vmap_stack(SDEI_STACK_SIZE, cpu_to_node(cpu)); 79 if (!p) 80 return -ENOMEM; 81 per_cpu(*ptr, cpu) = p; 82 83 return 0; 84 } 85 86 static int init_sdei_stacks(void) 87 { 88 int cpu; 89 int err = 0; 90 91 if (!IS_ENABLED(CONFIG_VMAP_STACK)) 92 return 0; 93 94 for_each_possible_cpu(cpu) { 95 err = _init_sdei_stack(&sdei_stack_normal_ptr, cpu); 96 if (err) 97 break; 98 err = _init_sdei_stack(&sdei_stack_critical_ptr, cpu); 99 if (err) 100 break; 101 } 102 103 if (err) 104 free_sdei_stacks(); 105 106 return err; 107 } 108 109 static void _free_sdei_scs(unsigned long * __percpu *ptr, int cpu) 110 { 111 void *s; 112 113 s = per_cpu(*ptr, cpu); 114 if (s) { 115 per_cpu(*ptr, cpu) = NULL; 116 scs_free(s); 117 } 118 } 119 120 static void free_sdei_scs(void) 121 { 122 int cpu; 123 124 for_each_possible_cpu(cpu) { 125 _free_sdei_scs(&sdei_shadow_call_stack_normal_ptr, cpu); 126 _free_sdei_scs(&sdei_shadow_call_stack_critical_ptr, cpu); 127 } 128 } 129 130 static int _init_sdei_scs(unsigned long * __percpu *ptr, int cpu) 131 { 132 void *s; 133 134 s = scs_alloc(cpu_to_node(cpu)); 135 if (!s) 136 return -ENOMEM; 137 per_cpu(*ptr, cpu) = s; 138 139 return 0; 140 } 141 142 static int init_sdei_scs(void) 143 { 144 int cpu; 145 int err = 0; 146 147 if (!IS_ENABLED(CONFIG_SHADOW_CALL_STACK)) 148 return 0; 149 150 for_each_possible_cpu(cpu) { 151 err = _init_sdei_scs(&sdei_shadow_call_stack_normal_ptr, cpu); 152 if (err) 153 break; 154 err = _init_sdei_scs(&sdei_shadow_call_stack_critical_ptr, cpu); 155 if (err) 156 break; 157 } 158 159 if (err) 160 free_sdei_scs(); 161 162 return err; 163 } 164 165 static bool on_sdei_normal_stack(unsigned long sp, unsigned long size, 166 struct stack_info *info) 167 { 168 unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_normal_ptr); 169 unsigned long high = low + SDEI_STACK_SIZE; 170 171 return on_stack(sp, size, low, high, STACK_TYPE_SDEI_NORMAL, info); 172 } 173 174 static bool on_sdei_critical_stack(unsigned long sp, unsigned long size, 175 struct stack_info *info) 176 { 177 unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_critical_ptr); 178 unsigned long high = low + SDEI_STACK_SIZE; 179 180 return on_stack(sp, size, low, high, STACK_TYPE_SDEI_CRITICAL, info); 181 } 182 183 bool _on_sdei_stack(unsigned long sp, unsigned long size, struct stack_info *info) 184 { 185 if (!IS_ENABLED(CONFIG_VMAP_STACK)) 186 return false; 187 188 if (on_sdei_critical_stack(sp, size, info)) 189 return true; 190 191 if (on_sdei_normal_stack(sp, size, info)) 192 return true; 193 194 return false; 195 } 196 197 unsigned long sdei_arch_get_entry_point(int conduit) 198 { 199 /* 200 * SDEI works between adjacent exception levels. If we booted at EL1 we 201 * assume a hypervisor is marshalling events. If we booted at EL2 and 202 * dropped to EL1 because we don't support VHE, then we can't support 203 * SDEI. 204 */ 205 if (is_hyp_mode_available() && !is_kernel_in_hyp_mode()) { 206 pr_err("Not supported on this hardware/boot configuration\n"); 207 goto out_err; 208 } 209 210 if (init_sdei_stacks()) 211 goto out_err; 212 213 if (init_sdei_scs()) 214 goto out_err_free_stacks; 215 216 sdei_exit_mode = (conduit == SMCCC_CONDUIT_HVC) ? SDEI_EXIT_HVC : SDEI_EXIT_SMC; 217 218 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 219 if (arm64_kernel_unmapped_at_el0()) { 220 unsigned long offset; 221 222 offset = (unsigned long)__sdei_asm_entry_trampoline - 223 (unsigned long)__entry_tramp_text_start; 224 return TRAMP_VALIAS + offset; 225 } else 226 #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ 227 return (unsigned long)__sdei_asm_handler; 228 229 out_err_free_stacks: 230 free_sdei_stacks(); 231 out_err: 232 return 0; 233 } 234 235 /* 236 * do_sdei_event() returns one of: 237 * SDEI_EV_HANDLED - success, return to the interrupted context. 238 * SDEI_EV_FAILED - failure, return this error code to firmare. 239 * virtual-address - success, return to this address. 240 */ 241 unsigned long __kprobes do_sdei_event(struct pt_regs *regs, 242 struct sdei_registered_event *arg) 243 { 244 u32 mode; 245 int i, err = 0; 246 int clobbered_registers = 4; 247 u64 elr = read_sysreg(elr_el1); 248 u32 kernel_mode = read_sysreg(CurrentEL) | 1; /* +SPSel */ 249 unsigned long vbar = read_sysreg(vbar_el1); 250 251 if (arm64_kernel_unmapped_at_el0()) 252 clobbered_registers++; 253 254 /* Retrieve the missing registers values */ 255 for (i = 0; i < clobbered_registers; i++) { 256 /* from within the handler, this call always succeeds */ 257 sdei_api_event_context(i, ®s->regs[i]); 258 } 259 260 err = sdei_event_handler(regs, arg); 261 if (err) 262 return SDEI_EV_FAILED; 263 264 if (elr != read_sysreg(elr_el1)) { 265 /* 266 * We took a synchronous exception from the SDEI handler. 267 * This could deadlock, and if you interrupt KVM it will 268 * hyp-panic instead. 269 */ 270 pr_warn("unsafe: exception during handler\n"); 271 } 272 273 mode = regs->pstate & (PSR_MODE32_BIT | PSR_MODE_MASK); 274 275 /* 276 * If we interrupted the kernel with interrupts masked, we always go 277 * back to wherever we came from. 278 */ 279 if (mode == kernel_mode && !interrupts_enabled(regs)) 280 return SDEI_EV_HANDLED; 281 282 /* 283 * Otherwise, we pretend this was an IRQ. This lets user space tasks 284 * receive signals before we return to them, and KVM to invoke it's 285 * world switch to do the same. 286 * 287 * See DDI0487B.a Table D1-7 'Vector offsets from vector table base 288 * address'. 289 */ 290 if (mode == kernel_mode) 291 return vbar + 0x280; 292 else if (mode & PSR_MODE32_BIT) 293 return vbar + 0x680; 294 295 return vbar + 0x480; 296 } 297