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 (!scs_is_enabled()) 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 unsigned long sdei_arch_get_entry_point(int conduit) 166 { 167 /* 168 * SDEI works between adjacent exception levels. If we booted at EL1 we 169 * assume a hypervisor is marshalling events. If we booted at EL2 and 170 * dropped to EL1 because we don't support VHE, then we can't support 171 * SDEI. 172 */ 173 if (is_hyp_nvhe()) { 174 pr_err("Not supported on this hardware/boot configuration\n"); 175 goto out_err; 176 } 177 178 if (init_sdei_stacks()) 179 goto out_err; 180 181 if (init_sdei_scs()) 182 goto out_err_free_stacks; 183 184 sdei_exit_mode = (conduit == SMCCC_CONDUIT_HVC) ? SDEI_EXIT_HVC : SDEI_EXIT_SMC; 185 186 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 187 if (arm64_kernel_unmapped_at_el0()) { 188 unsigned long offset; 189 190 offset = (unsigned long)__sdei_asm_entry_trampoline - 191 (unsigned long)__entry_tramp_text_start; 192 return TRAMP_VALIAS + offset; 193 } else 194 #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ 195 return (unsigned long)__sdei_asm_handler; 196 197 out_err_free_stacks: 198 free_sdei_stacks(); 199 out_err: 200 return 0; 201 } 202 203 /* 204 * do_sdei_event() returns one of: 205 * SDEI_EV_HANDLED - success, return to the interrupted context. 206 * SDEI_EV_FAILED - failure, return this error code to firmare. 207 * virtual-address - success, return to this address. 208 */ 209 unsigned long __kprobes do_sdei_event(struct pt_regs *regs, 210 struct sdei_registered_event *arg) 211 { 212 u32 mode; 213 int i, err = 0; 214 int clobbered_registers = 4; 215 u64 elr = read_sysreg(elr_el1); 216 u32 kernel_mode = read_sysreg(CurrentEL) | 1; /* +SPSel */ 217 unsigned long vbar = read_sysreg(vbar_el1); 218 219 if (arm64_kernel_unmapped_at_el0()) 220 clobbered_registers++; 221 222 /* Retrieve the missing registers values */ 223 for (i = 0; i < clobbered_registers; i++) { 224 /* from within the handler, this call always succeeds */ 225 sdei_api_event_context(i, ®s->regs[i]); 226 } 227 228 err = sdei_event_handler(regs, arg); 229 if (err) 230 return SDEI_EV_FAILED; 231 232 if (elr != read_sysreg(elr_el1)) { 233 /* 234 * We took a synchronous exception from the SDEI handler. 235 * This could deadlock, and if you interrupt KVM it will 236 * hyp-panic instead. 237 */ 238 pr_warn("unsafe: exception during handler\n"); 239 } 240 241 mode = regs->pstate & (PSR_MODE32_BIT | PSR_MODE_MASK); 242 243 /* 244 * If we interrupted the kernel with interrupts masked, we always go 245 * back to wherever we came from. 246 */ 247 if (mode == kernel_mode && !interrupts_enabled(regs)) 248 return SDEI_EV_HANDLED; 249 250 /* 251 * Otherwise, we pretend this was an IRQ. This lets user space tasks 252 * receive signals before we return to them, and KVM to invoke it's 253 * world switch to do the same. 254 * 255 * See DDI0487B.a Table D1-7 'Vector offsets from vector table base 256 * address'. 257 */ 258 if (mode == kernel_mode) 259 return vbar + 0x280; 260 else if (mode & PSR_MODE32_BIT) 261 return vbar + 0x680; 262 263 return vbar + 0x480; 264 } 265