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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
744c193e | 2 | #include <linux/extable.h> |
7c0f6ba6 | 3 | #include <linux/uaccess.h> |
b17b0153 | 4 | #include <linux/sched/debug.h> |
42b3a4cb | 5 | #include <xen/xen.h> |
b17b0153 | 6 | |
d5c8028b | 7 | #include <asm/fpu/internal.h> |
0d0efc07 | 8 | #include <asm/traps.h> |
81c2949f | 9 | #include <asm/kdebug.h> |
6d48583b | 10 | |
548acf19 | 11 | typedef bool (*ex_handler_t)(const struct exception_table_entry *, |
81fd9c18 JH |
12 | struct pt_regs *, int, unsigned long, |
13 | unsigned long); | |
548acf19 | 14 | |
70627654 PA |
15 | static inline unsigned long |
16 | ex_fixup_addr(const struct exception_table_entry *x) | |
17 | { | |
18 | return (unsigned long)&x->fixup + x->fixup; | |
19 | } | |
548acf19 TL |
20 | static inline ex_handler_t |
21 | ex_fixup_handler(const struct exception_table_entry *x) | |
22 | { | |
23 | return (ex_handler_t)((unsigned long)&x->handler + x->handler); | |
24 | } | |
6d48583b | 25 | |
80a3e394 | 26 | __visible bool ex_handler_default(const struct exception_table_entry *fixup, |
81fd9c18 JH |
27 | struct pt_regs *regs, int trapnr, |
28 | unsigned long error_code, | |
29 | unsigned long fault_addr) | |
6d48583b | 30 | { |
548acf19 TL |
31 | regs->ip = ex_fixup_addr(fixup); |
32 | return true; | |
33 | } | |
34 | EXPORT_SYMBOL(ex_handler_default); | |
35 | ||
80a3e394 | 36 | __visible bool ex_handler_fault(const struct exception_table_entry *fixup, |
81fd9c18 JH |
37 | struct pt_regs *regs, int trapnr, |
38 | unsigned long error_code, | |
39 | unsigned long fault_addr) | |
548acf19 TL |
40 | { |
41 | regs->ip = ex_fixup_addr(fixup); | |
42 | regs->ax = trapnr; | |
43 | return true; | |
44 | } | |
45 | EXPORT_SYMBOL_GPL(ex_handler_fault); | |
46 | ||
d5c8028b EB |
47 | /* |
48 | * Handler for when we fail to restore a task's FPU state. We should never get | |
49 | * here because the FPU state of a task using the FPU (task->thread.fpu.state) | |
50 | * should always be valid. However, past bugs have allowed userspace to set | |
51 | * reserved bits in the XSAVE area using PTRACE_SETREGSET or sys_rt_sigreturn(). | |
52 | * These caused XRSTOR to fail when switching to the task, leaking the FPU | |
53 | * registers of the task previously executing on the CPU. Mitigate this class | |
54 | * of vulnerability by restoring from the initial state (essentially, zeroing | |
55 | * out all the FPU registers) if we can't restore from the task's FPU state. | |
56 | */ | |
80a3e394 | 57 | __visible bool ex_handler_fprestore(const struct exception_table_entry *fixup, |
81fd9c18 JH |
58 | struct pt_regs *regs, int trapnr, |
59 | unsigned long error_code, | |
60 | unsigned long fault_addr) | |
d5c8028b EB |
61 | { |
62 | regs->ip = ex_fixup_addr(fixup); | |
63 | ||
64 | WARN_ONCE(1, "Bad FPU state detected at %pB, reinitializing FPU registers.", | |
65 | (void *)instruction_pointer(regs)); | |
66 | ||
67 | __copy_kernel_to_fpregs(&init_fpstate, -1); | |
68 | return true; | |
69 | } | |
70 | EXPORT_SYMBOL_GPL(ex_handler_fprestore); | |
71 | ||
75045f77 | 72 | __visible bool ex_handler_uaccess(const struct exception_table_entry *fixup, |
81fd9c18 JH |
73 | struct pt_regs *regs, int trapnr, |
74 | unsigned long error_code, | |
75 | unsigned long fault_addr) | |
75045f77 | 76 | { |
00c42373 | 77 | WARN_ONCE(trapnr == X86_TRAP_GP, "General protection fault in user access. Non-canonical address?"); |
75045f77 JH |
78 | regs->ip = ex_fixup_addr(fixup); |
79 | return true; | |
80 | } | |
81 | EXPORT_SYMBOL(ex_handler_uaccess); | |
82 | ||
278b917f YS |
83 | __visible bool ex_handler_copy(const struct exception_table_entry *fixup, |
84 | struct pt_regs *regs, int trapnr, | |
85 | unsigned long error_code, | |
86 | unsigned long fault_addr) | |
87 | { | |
88 | WARN_ONCE(trapnr == X86_TRAP_GP, "General protection fault in user access. Non-canonical address?"); | |
89 | regs->ip = ex_fixup_addr(fixup); | |
90 | regs->ax = trapnr; | |
91 | return true; | |
92 | } | |
93 | EXPORT_SYMBOL(ex_handler_copy); | |
94 | ||
80a3e394 | 95 | __visible bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup, |
81fd9c18 JH |
96 | struct pt_regs *regs, int trapnr, |
97 | unsigned long error_code, | |
98 | unsigned long fault_addr) | |
fbd70437 | 99 | { |
d75f773c | 100 | if (pr_warn_once("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pS)\n", |
81c2949f BP |
101 | (unsigned int)regs->cx, regs->ip, (void *)regs->ip)) |
102 | show_stack_regs(regs); | |
fbd70437 AL |
103 | |
104 | /* Pretend that the read succeeded and returned 0. */ | |
105 | regs->ip = ex_fixup_addr(fixup); | |
106 | regs->ax = 0; | |
107 | regs->dx = 0; | |
108 | return true; | |
109 | } | |
110 | EXPORT_SYMBOL(ex_handler_rdmsr_unsafe); | |
111 | ||
80a3e394 | 112 | __visible bool ex_handler_wrmsr_unsafe(const struct exception_table_entry *fixup, |
81fd9c18 JH |
113 | struct pt_regs *regs, int trapnr, |
114 | unsigned long error_code, | |
115 | unsigned long fault_addr) | |
fbd70437 | 116 | { |
d75f773c | 117 | if (pr_warn_once("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pS)\n", |
81c2949f BP |
118 | (unsigned int)regs->cx, (unsigned int)regs->dx, |
119 | (unsigned int)regs->ax, regs->ip, (void *)regs->ip)) | |
120 | show_stack_regs(regs); | |
fbd70437 AL |
121 | |
122 | /* Pretend that the write succeeded. */ | |
123 | regs->ip = ex_fixup_addr(fixup); | |
124 | return true; | |
125 | } | |
126 | EXPORT_SYMBOL(ex_handler_wrmsr_unsafe); | |
127 | ||
80a3e394 | 128 | __visible bool ex_handler_clear_fs(const struct exception_table_entry *fixup, |
81fd9c18 JH |
129 | struct pt_regs *regs, int trapnr, |
130 | unsigned long error_code, | |
131 | unsigned long fault_addr) | |
45e876f7 AL |
132 | { |
133 | if (static_cpu_has(X86_BUG_NULL_SEG)) | |
134 | asm volatile ("mov %0, %%fs" : : "rm" (__USER_DS)); | |
135 | asm volatile ("mov %0, %%fs" : : "rm" (0)); | |
81fd9c18 | 136 | return ex_handler_default(fixup, regs, trapnr, error_code, fault_addr); |
45e876f7 AL |
137 | } |
138 | EXPORT_SYMBOL(ex_handler_clear_fs); | |
139 | ||
a05d54c4 | 140 | enum handler_type ex_get_fault_handler_type(unsigned long ip) |
548acf19 TL |
141 | { |
142 | const struct exception_table_entry *e; | |
143 | ex_handler_t handler; | |
144 | ||
145 | e = search_exception_tables(ip); | |
146 | if (!e) | |
a05d54c4 | 147 | return EX_HANDLER_NONE; |
548acf19 | 148 | handler = ex_fixup_handler(e); |
a05d54c4 TL |
149 | if (handler == ex_handler_fault) |
150 | return EX_HANDLER_FAULT; | |
278b917f | 151 | else if (handler == ex_handler_uaccess || handler == ex_handler_copy) |
a05d54c4 TL |
152 | return EX_HANDLER_UACCESS; |
153 | else | |
154 | return EX_HANDLER_OTHER; | |
548acf19 TL |
155 | } |
156 | ||
81fd9c18 JH |
157 | int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code, |
158 | unsigned long fault_addr) | |
548acf19 TL |
159 | { |
160 | const struct exception_table_entry *e; | |
161 | ex_handler_t handler; | |
6d48583b HH |
162 | |
163 | #ifdef CONFIG_PNPBIOS | |
164 | if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) { | |
165 | extern u32 pnp_bios_fault_eip, pnp_bios_fault_esp; | |
166 | extern u32 pnp_bios_is_utter_crap; | |
167 | pnp_bios_is_utter_crap = 1; | |
168 | printk(KERN_CRIT "PNPBIOS fault.. attempting recovery.\n"); | |
169 | __asm__ volatile( | |
170 | "movl %0, %%esp\n\t" | |
171 | "jmp *%1\n\t" | |
172 | : : "g" (pnp_bios_fault_esp), "g" (pnp_bios_fault_eip)); | |
173 | panic("do_trap: can't hit this"); | |
174 | } | |
175 | #endif | |
176 | ||
548acf19 TL |
177 | e = search_exception_tables(regs->ip); |
178 | if (!e) | |
179 | return 0; | |
6d48583b | 180 | |
548acf19 | 181 | handler = ex_fixup_handler(e); |
81fd9c18 | 182 | return handler(e, regs, trapnr, error_code, fault_addr); |
6d48583b | 183 | } |
6a1ea279 | 184 | |
0e861fbb AL |
185 | extern unsigned int early_recursion_flag; |
186 | ||
6a1ea279 | 187 | /* Restricted version used during very early boot */ |
0e861fbb | 188 | void __init early_fixup_exception(struct pt_regs *regs, int trapnr) |
6a1ea279 | 189 | { |
0d0efc07 AL |
190 | /* Ignore early NMIs. */ |
191 | if (trapnr == X86_TRAP_NMI) | |
0e861fbb AL |
192 | return; |
193 | ||
194 | if (early_recursion_flag > 2) | |
195 | goto halt_loop; | |
196 | ||
fc0e81b2 AL |
197 | /* |
198 | * Old CPUs leave the high bits of CS on the stack | |
199 | * undefined. I'm not sure which CPUs do this, but at least | |
200 | * the 486 DX works this way. | |
42b3a4cb | 201 | * Xen pv domains are not using the default __KERNEL_CS. |
fc0e81b2 | 202 | */ |
42b3a4cb | 203 | if (!xen_pv_domain() && regs->cs != __KERNEL_CS) |
0e861fbb | 204 | goto fail; |
0d0efc07 | 205 | |
60a0e203 AL |
206 | /* |
207 | * The full exception fixup machinery is available as soon as | |
208 | * the early IDT is loaded. This means that it is the | |
209 | * responsibility of extable users to either function correctly | |
210 | * when handlers are invoked early or to simply avoid causing | |
211 | * exceptions before they're ready to handle them. | |
212 | * | |
213 | * This is better than filtering which handlers can be used, | |
214 | * because refusing to call a handler here is guaranteed to | |
215 | * result in a hard-to-debug panic. | |
216 | * | |
217 | * Keep in mind that not all vectors actually get here. Early | |
81fd9c18 | 218 | * page faults, for example, are special. |
60a0e203 | 219 | */ |
81fd9c18 | 220 | if (fixup_exception(regs, trapnr, regs->orig_ax, 0)) |
ae7ef45e | 221 | return; |
0e861fbb | 222 | |
15a416e8 AL |
223 | if (trapnr == X86_TRAP_UD) { |
224 | if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN) { | |
225 | /* Skip the ud2. */ | |
226 | regs->ip += LEN_UD2; | |
227 | return; | |
228 | } | |
229 | ||
230 | /* | |
231 | * If this was a BUG and report_bug returns or if this | |
232 | * was just a normal #UD, we want to continue onward and | |
233 | * crash. | |
234 | */ | |
235 | } | |
8a524f80 | 236 | |
0e861fbb AL |
237 | fail: |
238 | early_printk("PANIC: early exception 0x%02x IP %lx:%lx error %lx cr2 0x%lx\n", | |
239 | (unsigned)trapnr, (unsigned long)regs->cs, regs->ip, | |
240 | regs->orig_ax, read_cr2()); | |
241 | ||
242 | show_regs(regs); | |
243 | ||
244 | halt_loop: | |
245 | while (true) | |
246 | halt(); | |
6a1ea279 | 247 | } |