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