xref: /openbmc/linux/arch/x86/kernel/perf_regs.c (revision f7c35abe)
1 #include <linux/errno.h>
2 #include <linux/kernel.h>
3 #include <linux/sched.h>
4 #include <linux/sched/task_stack.h>
5 #include <linux/perf_event.h>
6 #include <linux/bug.h>
7 #include <linux/stddef.h>
8 #include <asm/perf_regs.h>
9 #include <asm/ptrace.h>
10 
11 #ifdef CONFIG_X86_32
12 #define PERF_REG_X86_MAX PERF_REG_X86_32_MAX
13 #else
14 #define PERF_REG_X86_MAX PERF_REG_X86_64_MAX
15 #endif
16 
17 #define PT_REGS_OFFSET(id, r) [id] = offsetof(struct pt_regs, r)
18 
19 static unsigned int pt_regs_offset[PERF_REG_X86_MAX] = {
20 	PT_REGS_OFFSET(PERF_REG_X86_AX, ax),
21 	PT_REGS_OFFSET(PERF_REG_X86_BX, bx),
22 	PT_REGS_OFFSET(PERF_REG_X86_CX, cx),
23 	PT_REGS_OFFSET(PERF_REG_X86_DX, dx),
24 	PT_REGS_OFFSET(PERF_REG_X86_SI, si),
25 	PT_REGS_OFFSET(PERF_REG_X86_DI, di),
26 	PT_REGS_OFFSET(PERF_REG_X86_BP, bp),
27 	PT_REGS_OFFSET(PERF_REG_X86_SP, sp),
28 	PT_REGS_OFFSET(PERF_REG_X86_IP, ip),
29 	PT_REGS_OFFSET(PERF_REG_X86_FLAGS, flags),
30 	PT_REGS_OFFSET(PERF_REG_X86_CS, cs),
31 	PT_REGS_OFFSET(PERF_REG_X86_SS, ss),
32 #ifdef CONFIG_X86_32
33 	PT_REGS_OFFSET(PERF_REG_X86_DS, ds),
34 	PT_REGS_OFFSET(PERF_REG_X86_ES, es),
35 	PT_REGS_OFFSET(PERF_REG_X86_FS, fs),
36 	PT_REGS_OFFSET(PERF_REG_X86_GS, gs),
37 #else
38 	/*
39 	 * The pt_regs struct does not store
40 	 * ds, es, fs, gs in 64 bit mode.
41 	 */
42 	(unsigned int) -1,
43 	(unsigned int) -1,
44 	(unsigned int) -1,
45 	(unsigned int) -1,
46 #endif
47 #ifdef CONFIG_X86_64
48 	PT_REGS_OFFSET(PERF_REG_X86_R8, r8),
49 	PT_REGS_OFFSET(PERF_REG_X86_R9, r9),
50 	PT_REGS_OFFSET(PERF_REG_X86_R10, r10),
51 	PT_REGS_OFFSET(PERF_REG_X86_R11, r11),
52 	PT_REGS_OFFSET(PERF_REG_X86_R12, r12),
53 	PT_REGS_OFFSET(PERF_REG_X86_R13, r13),
54 	PT_REGS_OFFSET(PERF_REG_X86_R14, r14),
55 	PT_REGS_OFFSET(PERF_REG_X86_R15, r15),
56 #endif
57 };
58 
59 u64 perf_reg_value(struct pt_regs *regs, int idx)
60 {
61 	if (WARN_ON_ONCE(idx >= ARRAY_SIZE(pt_regs_offset)))
62 		return 0;
63 
64 	return regs_get_register(regs, pt_regs_offset[idx]);
65 }
66 
67 #define REG_RESERVED (~((1ULL << PERF_REG_X86_MAX) - 1ULL))
68 
69 #ifdef CONFIG_X86_32
70 int perf_reg_validate(u64 mask)
71 {
72 	if (!mask || mask & REG_RESERVED)
73 		return -EINVAL;
74 
75 	return 0;
76 }
77 
78 u64 perf_reg_abi(struct task_struct *task)
79 {
80 	return PERF_SAMPLE_REGS_ABI_32;
81 }
82 
83 void perf_get_regs_user(struct perf_regs *regs_user,
84 			struct pt_regs *regs,
85 			struct pt_regs *regs_user_copy)
86 {
87 	regs_user->regs = task_pt_regs(current);
88 	regs_user->abi = perf_reg_abi(current);
89 }
90 #else /* CONFIG_X86_64 */
91 #define REG_NOSUPPORT ((1ULL << PERF_REG_X86_DS) | \
92 		       (1ULL << PERF_REG_X86_ES) | \
93 		       (1ULL << PERF_REG_X86_FS) | \
94 		       (1ULL << PERF_REG_X86_GS))
95 
96 int perf_reg_validate(u64 mask)
97 {
98 	if (!mask || mask & REG_RESERVED)
99 		return -EINVAL;
100 
101 	if (mask & REG_NOSUPPORT)
102 		return -EINVAL;
103 
104 	return 0;
105 }
106 
107 u64 perf_reg_abi(struct task_struct *task)
108 {
109 	if (test_tsk_thread_flag(task, TIF_IA32))
110 		return PERF_SAMPLE_REGS_ABI_32;
111 	else
112 		return PERF_SAMPLE_REGS_ABI_64;
113 }
114 
115 void perf_get_regs_user(struct perf_regs *regs_user,
116 			struct pt_regs *regs,
117 			struct pt_regs *regs_user_copy)
118 {
119 	struct pt_regs *user_regs = task_pt_regs(current);
120 
121 	/*
122 	 * If we're in an NMI that interrupted task_pt_regs setup, then
123 	 * we can't sample user regs at all.  This check isn't really
124 	 * sufficient, though, as we could be in an NMI inside an interrupt
125 	 * that happened during task_pt_regs setup.
126 	 */
127 	if (regs->sp > (unsigned long)&user_regs->r11 &&
128 	    regs->sp <= (unsigned long)(user_regs + 1)) {
129 		regs_user->abi = PERF_SAMPLE_REGS_ABI_NONE;
130 		regs_user->regs = NULL;
131 		return;
132 	}
133 
134 	/*
135 	 * These registers are always saved on 64-bit syscall entry.
136 	 * On 32-bit entry points, they are saved too except r8..r11.
137 	 */
138 	regs_user_copy->ip = user_regs->ip;
139 	regs_user_copy->ax = user_regs->ax;
140 	regs_user_copy->cx = user_regs->cx;
141 	regs_user_copy->dx = user_regs->dx;
142 	regs_user_copy->si = user_regs->si;
143 	regs_user_copy->di = user_regs->di;
144 	regs_user_copy->r8 = user_regs->r8;
145 	regs_user_copy->r9 = user_regs->r9;
146 	regs_user_copy->r10 = user_regs->r10;
147 	regs_user_copy->r11 = user_regs->r11;
148 	regs_user_copy->orig_ax = user_regs->orig_ax;
149 	regs_user_copy->flags = user_regs->flags;
150 	regs_user_copy->sp = user_regs->sp;
151 	regs_user_copy->cs = user_regs->cs;
152 	regs_user_copy->ss = user_regs->ss;
153 
154 	/*
155 	 * Most system calls don't save these registers, don't report them.
156 	 */
157 	regs_user_copy->bx = -1;
158 	regs_user_copy->bp = -1;
159 	regs_user_copy->r12 = -1;
160 	regs_user_copy->r13 = -1;
161 	regs_user_copy->r14 = -1;
162 	regs_user_copy->r15 = -1;
163 
164 	/*
165 	 * For this to be at all useful, we need a reasonable guess for
166 	 * the ABI.  Be careful: we're in NMI context, and we're
167 	 * considering current to be the current task, so we should
168 	 * be careful not to look at any other percpu variables that might
169 	 * change during context switches.
170 	 */
171 	regs_user->abi = user_64bit_mode(user_regs) ?
172 		PERF_SAMPLE_REGS_ABI_64 : PERF_SAMPLE_REGS_ABI_32;
173 
174 	regs_user->regs = regs_user_copy;
175 }
176 #endif /* CONFIG_X86_32 */
177