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
22static 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
31const char *stack_type_name(enum stack_type type)
32{
33	BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
34
35	if (type == STACK_TYPE_TASK)
36		return "TASK";
37
38	if (type == STACK_TYPE_IRQ)
39		return "IRQ";
40
41	if (type == STACK_TYPE_SOFTIRQ)
42		return "SOFTIRQ";
43
44	if (type == STACK_TYPE_ENTRY) {
45		/*
46		 * On 64-bit, we have a generic entry stack that we
47		 * use for all the kernel entry points, including
48		 * SYSENTER.
49		 */
50		return "ENTRY_TRAMPOLINE";
51	}
52
53	if (type >= STACK_TYPE_EXCEPTION && type <= STACK_TYPE_EXCEPTION_LAST)
54		return exception_stack_names[type - STACK_TYPE_EXCEPTION];
55
56	return NULL;
57}
58
59/**
60 * struct estack_pages - Page descriptor for exception stacks
61 * @offs:	Offset from the start of the exception stack area
62 * @size:	Size of the exception stack
63 * @type:	Type to store in the stack_info struct
64 */
65struct estack_pages {
66	u32	offs;
67	u16	size;
68	u16	type;
69};
70
71#define EPAGERANGE(st)							\
72	[PFN_DOWN(CEA_ESTACK_OFFS(st)) ...				\
73	 PFN_DOWN(CEA_ESTACK_OFFS(st) + CEA_ESTACK_SIZE(st) - 1)] = {	\
74		.offs	= CEA_ESTACK_OFFS(st),				\
75		.size	= CEA_ESTACK_SIZE(st),				\
76		.type	= STACK_TYPE_EXCEPTION + ESTACK_ ##st, }
77
78/*
79 * Array of exception stack page descriptors. If the stack is larger than
80 * PAGE_SIZE, all pages covering a particular stack will have the same
81 * info. The guard pages including the not mapped DB2 stack are zeroed
82 * out.
83 */
84static const
85struct estack_pages estack_pages[CEA_ESTACK_PAGES] ____cacheline_aligned = {
86	EPAGERANGE(DF),
87	EPAGERANGE(NMI),
88	EPAGERANGE(DB),
89	EPAGERANGE(MCE),
90	EPAGERANGE(VC),
91	EPAGERANGE(VC2),
92};
93
94static __always_inline bool in_exception_stack(unsigned long *stack, struct stack_info *info)
95{
96	unsigned long begin, end, stk = (unsigned long)stack;
97	const struct estack_pages *ep;
98	struct pt_regs *regs;
99	unsigned int k;
100
101	BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
102
103	begin = (unsigned long)__this_cpu_read(cea_exception_stacks);
104	/*
105	 * Handle the case where stack trace is collected _before_
106	 * cea_exception_stacks had been initialized.
107	 */
108	if (!begin)
109		return false;
110
111	end = begin + sizeof(struct cea_exception_stacks);
112	/* Bail if @stack is outside the exception stack area. */
113	if (stk < begin || stk >= end)
114		return false;
115
116	/* Calc page offset from start of exception stacks */
117	k = (stk - begin) >> PAGE_SHIFT;
118	/* Lookup the page descriptor */
119	ep = &estack_pages[k];
120	/* Guard page? */
121	if (!ep->size)
122		return false;
123
124	begin += (unsigned long)ep->offs;
125	end = begin + (unsigned long)ep->size;
126	regs = (struct pt_regs *)end - 1;
127
128	info->type	= ep->type;
129	info->begin	= (unsigned long *)begin;
130	info->end	= (unsigned long *)end;
131	info->next_sp	= (unsigned long *)regs->sp;
132	return true;
133}
134
135static __always_inline bool in_irq_stack(unsigned long *stack, struct stack_info *info)
136{
137	unsigned long *end = (unsigned long *)this_cpu_read(pcpu_hot.hardirq_stack_ptr);
138	unsigned long *begin;
139
140	/*
141	 * @end points directly to the top most stack entry to avoid a -8
142	 * adjustment in the stack switch hotpath. Adjust it back before
143	 * calculating @begin.
144	 */
145	end++;
146	begin = end - (IRQ_STACK_SIZE / sizeof(long));
147
148	/*
149	 * Due to the switching logic RSP can never be == @end because the
150	 * final operation is 'popq %rsp' which means after that RSP points
151	 * to the original stack and not to @end.
152	 */
153	if (stack < begin || stack >= end)
154		return false;
155
156	info->type	= STACK_TYPE_IRQ;
157	info->begin	= begin;
158	info->end	= end;
159
160	/*
161	 * The next stack pointer is stored at the top of the irq stack
162	 * before switching to the irq stack. Actual stack entries are all
163	 * below that.
164	 */
165	info->next_sp = (unsigned long *)*(end - 1);
166
167	return true;
168}
169
170bool noinstr get_stack_info_noinstr(unsigned long *stack, struct task_struct *task,
171				    struct stack_info *info)
172{
173	if (in_task_stack(stack, task, info))
174		return true;
175
176	if (task != current)
177		return false;
178
179	if (in_exception_stack(stack, info))
180		return true;
181
182	if (in_irq_stack(stack, info))
183		return true;
184
185	if (in_entry_stack(stack, info))
186		return true;
187
188	return false;
189}
190
191int get_stack_info(unsigned long *stack, struct task_struct *task,
192		   struct stack_info *info, unsigned long *visit_mask)
193{
194	task = task ? : current;
195
196	if (!stack)
197		goto unknown;
198
199	if (!get_stack_info_noinstr(stack, task, info))
200		goto unknown;
201
202	/*
203	 * Make sure we don't iterate through any given stack more than once.
204	 * If it comes up a second time then there's something wrong going on:
205	 * just break out and report an unknown stack type.
206	 */
207	if (visit_mask) {
208		if (*visit_mask & (1UL << info->type)) {
209			if (task == current)
210				printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n", info->type);
211			goto unknown;
212		}
213		*visit_mask |= 1UL << info->type;
214	}
215
216	return 0;
217
218unknown:
219	info->type = STACK_TYPE_UNKNOWN;
220	return -EINVAL;
221}
222