1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 1991, 1992 Linus Torvalds
4 * Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
5 */
6 #include <linux/sched/debug.h>
7 #include <linux/kallsyms.h>
8 #include <linux/kprobes.h>
9 #include <linux/uaccess.h>
10 #include <linux/hardirq.h>
11 #include <linux/kdebug.h>
12 #include <linux/export.h>
13 #include <linux/ptrace.h>
14 #include <linux/kexec.h>
15 #include <linux/sysfs.h>
16 #include <linux/bug.h>
17 #include <linux/nmi.h>
18
19 #include <asm/cpu_entry_area.h>
20 #include <asm/stacktrace.h>
21
22 static const char * const exception_stack_names[] = {
23 [ ESTACK_DF ] = "#DF",
24 [ ESTACK_NMI ] = "NMI",
25 [ ESTACK_DB ] = "#DB",
26 [ ESTACK_MCE ] = "#MC",
27 [ ESTACK_VC ] = "#VC",
28 [ ESTACK_VC2 ] = "#VC2",
29 };
30
stack_type_name(enum stack_type type)31 const char *stack_type_name(enum stack_type type)
32 {
33 BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
34
35 if (type == STACK_TYPE_IRQ)
36 return "IRQ";
37
38 if (type == STACK_TYPE_ENTRY) {
39 /*
40 * On 64-bit, we have a generic entry stack that we
41 * use for all the kernel entry points, including
42 * SYSENTER.
43 */
44 return "ENTRY_TRAMPOLINE";
45 }
46
47 if (type >= STACK_TYPE_EXCEPTION && type <= STACK_TYPE_EXCEPTION_LAST)
48 return exception_stack_names[type - STACK_TYPE_EXCEPTION];
49
50 return NULL;
51 }
52
53 /**
54 * struct estack_pages - Page descriptor for exception stacks
55 * @offs: Offset from the start of the exception stack area
56 * @size: Size of the exception stack
57 * @type: Type to store in the stack_info struct
58 */
59 struct estack_pages {
60 u32 offs;
61 u16 size;
62 u16 type;
63 };
64
65 #define EPAGERANGE(st) \
66 [PFN_DOWN(CEA_ESTACK_OFFS(st)) ... \
67 PFN_DOWN(CEA_ESTACK_OFFS(st) + CEA_ESTACK_SIZE(st) - 1)] = { \
68 .offs = CEA_ESTACK_OFFS(st), \
69 .size = CEA_ESTACK_SIZE(st), \
70 .type = STACK_TYPE_EXCEPTION + ESTACK_ ##st, }
71
72 /*
73 * Array of exception stack page descriptors. If the stack is larger than
74 * PAGE_SIZE, all pages covering a particular stack will have the same
75 * info. The guard pages including the not mapped DB2 stack are zeroed
76 * out.
77 */
78 static const
79 struct estack_pages estack_pages[CEA_ESTACK_PAGES] ____cacheline_aligned = {
80 EPAGERANGE(DF),
81 EPAGERANGE(NMI),
82 EPAGERANGE(DB),
83 EPAGERANGE(MCE),
84 EPAGERANGE(VC),
85 EPAGERANGE(VC2),
86 };
87
in_exception_stack(unsigned long * stack,struct stack_info * info)88 static __always_inline bool in_exception_stack(unsigned long *stack, struct stack_info *info)
89 {
90 unsigned long begin, end, stk = (unsigned long)stack;
91 const struct estack_pages *ep;
92 struct pt_regs *regs;
93 unsigned int k;
94
95 BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
96
97 begin = (unsigned long)__this_cpu_read(cea_exception_stacks);
98 /*
99 * Handle the case where stack trace is collected _before_
100 * cea_exception_stacks had been initialized.
101 */
102 if (!begin)
103 return false;
104
105 end = begin + sizeof(struct cea_exception_stacks);
106 /* Bail if @stack is outside the exception stack area. */
107 if (stk < begin || stk >= end)
108 return false;
109
110 /* Calc page offset from start of exception stacks */
111 k = (stk - begin) >> PAGE_SHIFT;
112 /* Lookup the page descriptor */
113 ep = &estack_pages[k];
114 /* Guard page? */
115 if (!ep->size)
116 return false;
117
118 begin += (unsigned long)ep->offs;
119 end = begin + (unsigned long)ep->size;
120 regs = (struct pt_regs *)end - 1;
121
122 info->type = ep->type;
123 info->begin = (unsigned long *)begin;
124 info->end = (unsigned long *)end;
125 info->next_sp = (unsigned long *)regs->sp;
126 return true;
127 }
128
in_irq_stack(unsigned long * stack,struct stack_info * info)129 static __always_inline bool in_irq_stack(unsigned long *stack, struct stack_info *info)
130 {
131 unsigned long *end = (unsigned long *)this_cpu_read(hardirq_stack_ptr);
132 unsigned long *begin;
133
134 /*
135 * @end points directly to the top most stack entry to avoid a -8
136 * adjustment in the stack switch hotpath. Adjust it back before
137 * calculating @begin.
138 */
139 end++;
140 begin = end - (IRQ_STACK_SIZE / sizeof(long));
141
142 /*
143 * Due to the switching logic RSP can never be == @end because the
144 * final operation is 'popq %rsp' which means after that RSP points
145 * to the original stack and not to @end.
146 */
147 if (stack < begin || stack >= end)
148 return false;
149
150 info->type = STACK_TYPE_IRQ;
151 info->begin = begin;
152 info->end = end;
153
154 /*
155 * The next stack pointer is stored at the top of the irq stack
156 * before switching to the irq stack. Actual stack entries are all
157 * below that.
158 */
159 info->next_sp = (unsigned long *)*(end - 1);
160
161 return true;
162 }
163
get_stack_info_noinstr(unsigned long * stack,struct task_struct * task,struct stack_info * info)164 bool noinstr get_stack_info_noinstr(unsigned long *stack, struct task_struct *task,
165 struct stack_info *info)
166 {
167 if (in_task_stack(stack, task, info))
168 return true;
169
170 if (task != current)
171 return false;
172
173 if (in_exception_stack(stack, info))
174 return true;
175
176 if (in_irq_stack(stack, info))
177 return true;
178
179 if (in_entry_stack(stack, info))
180 return true;
181
182 return false;
183 }
184
get_stack_info(unsigned long * stack,struct task_struct * task,struct stack_info * info,unsigned long * visit_mask)185 int get_stack_info(unsigned long *stack, struct task_struct *task,
186 struct stack_info *info, unsigned long *visit_mask)
187 {
188 task = task ? : current;
189
190 if (!stack)
191 goto unknown;
192
193 if (!get_stack_info_noinstr(stack, task, info))
194 goto unknown;
195
196 /*
197 * Make sure we don't iterate through any given stack more than once.
198 * If it comes up a second time then there's something wrong going on:
199 * just break out and report an unknown stack type.
200 */
201 if (visit_mask) {
202 if (*visit_mask & (1UL << info->type)) {
203 if (task == current)
204 printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n", info->type);
205 goto unknown;
206 }
207 *visit_mask |= 1UL << info->type;
208 }
209
210 return 0;
211
212 unknown:
213 info->type = STACK_TYPE_UNKNOWN;
214 return -EINVAL;
215 }
216