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
_free_sdei_stack(unsigned long * __percpu * ptr,int cpu)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
free_sdei_stacks(void)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
_init_sdei_stack(unsigned long * __percpu * ptr,int cpu)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
init_sdei_stacks(void)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
_free_sdei_scs(unsigned long * __percpu * ptr,int cpu)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
free_sdei_scs(void)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
_init_sdei_scs(unsigned long * __percpu * ptr,int cpu)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
init_sdei_scs(void)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
on_sdei_normal_stack(unsigned long sp,struct stack_info * info)165 static bool on_sdei_normal_stack(unsigned long sp, struct stack_info *info)
166 {
167 unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_normal_ptr);
168 unsigned long high = low + SDEI_STACK_SIZE;
169
170 return on_stack(sp, low, high, STACK_TYPE_SDEI_NORMAL, info);
171 }
172
on_sdei_critical_stack(unsigned long sp,struct stack_info * info)173 static bool on_sdei_critical_stack(unsigned long sp, struct stack_info *info)
174 {
175 unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_critical_ptr);
176 unsigned long high = low + SDEI_STACK_SIZE;
177
178 return on_stack(sp, low, high, STACK_TYPE_SDEI_CRITICAL, info);
179 }
180
_on_sdei_stack(unsigned long sp,struct stack_info * info)181 bool _on_sdei_stack(unsigned long sp, struct stack_info *info)
182 {
183 if (!IS_ENABLED(CONFIG_VMAP_STACK))
184 return false;
185
186 if (on_sdei_critical_stack(sp, info))
187 return true;
188
189 if (on_sdei_normal_stack(sp, info))
190 return true;
191
192 return false;
193 }
194
sdei_arch_get_entry_point(int conduit)195 unsigned long sdei_arch_get_entry_point(int conduit)
196 {
197 /*
198 * SDEI works between adjacent exception levels. If we booted at EL1 we
199 * assume a hypervisor is marshalling events. If we booted at EL2 and
200 * dropped to EL1 because we don't support VHE, then we can't support
201 * SDEI.
202 */
203 if (is_hyp_mode_available() && !is_kernel_in_hyp_mode()) {
204 pr_err("Not supported on this hardware/boot configuration\n");
205 goto out_err;
206 }
207
208 if (init_sdei_stacks())
209 goto out_err;
210
211 if (init_sdei_scs())
212 goto out_err_free_stacks;
213
214 sdei_exit_mode = (conduit == SMCCC_CONDUIT_HVC) ? SDEI_EXIT_HVC : SDEI_EXIT_SMC;
215
216 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
217 if (arm64_kernel_unmapped_at_el0()) {
218 unsigned long offset;
219
220 offset = (unsigned long)__sdei_asm_entry_trampoline -
221 (unsigned long)__entry_tramp_text_start;
222 return TRAMP_VALIAS + offset;
223 } else
224 #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
225 return (unsigned long)__sdei_asm_handler;
226
227 out_err_free_stacks:
228 free_sdei_stacks();
229 out_err:
230 return 0;
231 }
232
233 /*
234 * __sdei_handler() returns one of:
235 * SDEI_EV_HANDLED - success, return to the interrupted context.
236 * SDEI_EV_FAILED - failure, return this error code to firmare.
237 * virtual-address - success, return to this address.
238 */
_sdei_handler(struct pt_regs * regs,struct sdei_registered_event * arg)239 static __kprobes unsigned long _sdei_handler(struct pt_regs *regs,
240 struct sdei_registered_event *arg)
241 {
242 u32 mode;
243 int i, err = 0;
244 int clobbered_registers = 4;
245 u64 elr = read_sysreg(elr_el1);
246 u32 kernel_mode = read_sysreg(CurrentEL) | 1; /* +SPSel */
247 unsigned long vbar = read_sysreg(vbar_el1);
248
249 if (arm64_kernel_unmapped_at_el0())
250 clobbered_registers++;
251
252 /* Retrieve the missing registers values */
253 for (i = 0; i < clobbered_registers; i++) {
254 /* from within the handler, this call always succeeds */
255 sdei_api_event_context(i, ®s->regs[i]);
256 }
257
258 /*
259 * We didn't take an exception to get here, set PAN. UAO will be cleared
260 * by sdei_event_handler()s force_uaccess_begin() call.
261 */
262 __uaccess_enable_hw_pan();
263
264 err = sdei_event_handler(regs, arg);
265 if (err)
266 return SDEI_EV_FAILED;
267
268 if (elr != read_sysreg(elr_el1)) {
269 /*
270 * We took a synchronous exception from the SDEI handler.
271 * This could deadlock, and if you interrupt KVM it will
272 * hyp-panic instead.
273 */
274 pr_warn("unsafe: exception during handler\n");
275 }
276
277 mode = regs->pstate & (PSR_MODE32_BIT | PSR_MODE_MASK);
278
279 /*
280 * If we interrupted the kernel with interrupts masked, we always go
281 * back to wherever we came from.
282 */
283 if (mode == kernel_mode && !interrupts_enabled(regs))
284 return SDEI_EV_HANDLED;
285
286 /*
287 * Otherwise, we pretend this was an IRQ. This lets user space tasks
288 * receive signals before we return to them, and KVM to invoke it's
289 * world switch to do the same.
290 *
291 * See DDI0487B.a Table D1-7 'Vector offsets from vector table base
292 * address'.
293 */
294 if (mode == kernel_mode)
295 return vbar + 0x280;
296 else if (mode & PSR_MODE32_BIT)
297 return vbar + 0x680;
298
299 return vbar + 0x480;
300 }
301
302
303 asmlinkage noinstr unsigned long
__sdei_handler(struct pt_regs * regs,struct sdei_registered_event * arg)304 __sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg)
305 {
306 unsigned long ret;
307
308 arm64_enter_nmi(regs);
309
310 ret = _sdei_handler(regs, arg);
311
312 arm64_exit_nmi(regs);
313
314 return ret;
315 }
316