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 (!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
sdei_arch_get_entry_point(int conduit)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 */
do_sdei_event(struct pt_regs * regs,struct sdei_registered_event * arg)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