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,unsigned long size,struct stack_info * info)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
on_sdei_critical_stack(unsigned long sp,unsigned long size,struct stack_info * info)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
_on_sdei_stack(unsigned long sp,unsigned long size,struct stack_info * info)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
sdei_arch_get_entry_point(int conduit)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_nvhe()) {
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 */
do_sdei_event(struct pt_regs * regs,struct sdei_registered_event * arg)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