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 DEFINE_PER_CPU(struct sdei_registered_event *, sdei_active_normal_event); 51 DEFINE_PER_CPU(struct sdei_registered_event *, sdei_active_critical_event); 52 53 static void _free_sdei_stack(unsigned long * __percpu *ptr, int cpu) 54 { 55 unsigned long *p; 56 57 p = per_cpu(*ptr, cpu); 58 if (p) { 59 per_cpu(*ptr, cpu) = NULL; 60 vfree(p); 61 } 62 } 63 64 static void free_sdei_stacks(void) 65 { 66 int cpu; 67 68 if (!IS_ENABLED(CONFIG_VMAP_STACK)) 69 return; 70 71 for_each_possible_cpu(cpu) { 72 _free_sdei_stack(&sdei_stack_normal_ptr, cpu); 73 _free_sdei_stack(&sdei_stack_critical_ptr, cpu); 74 } 75 } 76 77 static int _init_sdei_stack(unsigned long * __percpu *ptr, int cpu) 78 { 79 unsigned long *p; 80 81 p = arch_alloc_vmap_stack(SDEI_STACK_SIZE, cpu_to_node(cpu)); 82 if (!p) 83 return -ENOMEM; 84 per_cpu(*ptr, cpu) = p; 85 86 return 0; 87 } 88 89 static int init_sdei_stacks(void) 90 { 91 int cpu; 92 int err = 0; 93 94 if (!IS_ENABLED(CONFIG_VMAP_STACK)) 95 return 0; 96 97 for_each_possible_cpu(cpu) { 98 err = _init_sdei_stack(&sdei_stack_normal_ptr, cpu); 99 if (err) 100 break; 101 err = _init_sdei_stack(&sdei_stack_critical_ptr, cpu); 102 if (err) 103 break; 104 } 105 106 if (err) 107 free_sdei_stacks(); 108 109 return err; 110 } 111 112 static void _free_sdei_scs(unsigned long * __percpu *ptr, int cpu) 113 { 114 void *s; 115 116 s = per_cpu(*ptr, cpu); 117 if (s) { 118 per_cpu(*ptr, cpu) = NULL; 119 scs_free(s); 120 } 121 } 122 123 static void free_sdei_scs(void) 124 { 125 int cpu; 126 127 for_each_possible_cpu(cpu) { 128 _free_sdei_scs(&sdei_shadow_call_stack_normal_ptr, cpu); 129 _free_sdei_scs(&sdei_shadow_call_stack_critical_ptr, cpu); 130 } 131 } 132 133 static int _init_sdei_scs(unsigned long * __percpu *ptr, int cpu) 134 { 135 void *s; 136 137 s = scs_alloc(cpu_to_node(cpu)); 138 if (!s) 139 return -ENOMEM; 140 per_cpu(*ptr, cpu) = s; 141 142 return 0; 143 } 144 145 static int init_sdei_scs(void) 146 { 147 int cpu; 148 int err = 0; 149 150 if (!scs_is_enabled()) 151 return 0; 152 153 for_each_possible_cpu(cpu) { 154 err = _init_sdei_scs(&sdei_shadow_call_stack_normal_ptr, cpu); 155 if (err) 156 break; 157 err = _init_sdei_scs(&sdei_shadow_call_stack_critical_ptr, cpu); 158 if (err) 159 break; 160 } 161 162 if (err) 163 free_sdei_scs(); 164 165 return err; 166 } 167 168 unsigned long sdei_arch_get_entry_point(int conduit) 169 { 170 /* 171 * SDEI works between adjacent exception levels. If we booted at EL1 we 172 * assume a hypervisor is marshalling events. If we booted at EL2 and 173 * dropped to EL1 because we don't support VHE, then we can't support 174 * SDEI. 175 */ 176 if (is_hyp_nvhe()) { 177 pr_err("Not supported on this hardware/boot configuration\n"); 178 goto out_err; 179 } 180 181 if (init_sdei_stacks()) 182 goto out_err; 183 184 if (init_sdei_scs()) 185 goto out_err_free_stacks; 186 187 sdei_exit_mode = (conduit == SMCCC_CONDUIT_HVC) ? SDEI_EXIT_HVC : SDEI_EXIT_SMC; 188 189 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 190 if (arm64_kernel_unmapped_at_el0()) { 191 unsigned long offset; 192 193 offset = (unsigned long)__sdei_asm_entry_trampoline - 194 (unsigned long)__entry_tramp_text_start; 195 return TRAMP_VALIAS + offset; 196 } else 197 #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ 198 return (unsigned long)__sdei_asm_handler; 199 200 out_err_free_stacks: 201 free_sdei_stacks(); 202 out_err: 203 return 0; 204 } 205 206 /* 207 * do_sdei_event() returns one of: 208 * SDEI_EV_HANDLED - success, return to the interrupted context. 209 * SDEI_EV_FAILED - failure, return this error code to firmare. 210 * virtual-address - success, return to this address. 211 */ 212 unsigned long __kprobes do_sdei_event(struct pt_regs *regs, 213 struct sdei_registered_event *arg) 214 { 215 u32 mode; 216 int i, err = 0; 217 int clobbered_registers = 4; 218 u64 elr = read_sysreg(elr_el1); 219 u32 kernel_mode = read_sysreg(CurrentEL) | 1; /* +SPSel */ 220 unsigned long vbar = read_sysreg(vbar_el1); 221 222 if (arm64_kernel_unmapped_at_el0()) 223 clobbered_registers++; 224 225 /* Retrieve the missing registers values */ 226 for (i = 0; i < clobbered_registers; i++) { 227 /* from within the handler, this call always succeeds */ 228 sdei_api_event_context(i, ®s->regs[i]); 229 } 230 231 err = sdei_event_handler(regs, arg); 232 if (err) 233 return SDEI_EV_FAILED; 234 235 if (elr != read_sysreg(elr_el1)) { 236 /* 237 * We took a synchronous exception from the SDEI handler. 238 * This could deadlock, and if you interrupt KVM it will 239 * hyp-panic instead. 240 */ 241 pr_warn("unsafe: exception during handler\n"); 242 } 243 244 mode = regs->pstate & (PSR_MODE32_BIT | PSR_MODE_MASK); 245 246 /* 247 * If we interrupted the kernel with interrupts masked, we always go 248 * back to wherever we came from. 249 */ 250 if (mode == kernel_mode && !interrupts_enabled(regs)) 251 return SDEI_EV_HANDLED; 252 253 /* 254 * Otherwise, we pretend this was an IRQ. This lets user space tasks 255 * receive signals before we return to them, and KVM to invoke it's 256 * world switch to do the same. 257 * 258 * See DDI0487B.a Table D1-7 'Vector offsets from vector table base 259 * address'. 260 */ 261 if (mode == kernel_mode) 262 return vbar + 0x280; 263 else if (mode & PSR_MODE32_BIT) 264 return vbar + 0x680; 265 266 return vbar + 0x480; 267 } 268