xref: /openbmc/linux/arch/x86/kernel/perf_regs.c (revision 375d4bfd)
1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/errno.h>
3 #include <linux/kernel.h>
4 #include <linux/sched.h>
5 #include <linux/sched/task_stack.h>
6 #include <linux/perf_event.h>
7 #include <linux/bug.h>
8 #include <linux/stddef.h>
9 #include <asm/perf_regs.h>
10 #include <asm/ptrace.h>
11 
12 #ifdef CONFIG_X86_32
13 #define PERF_REG_X86_MAX PERF_REG_X86_32_MAX
14 #else
15 #define PERF_REG_X86_MAX PERF_REG_X86_64_MAX
16 #endif
17 
18 #define PT_REGS_OFFSET(id, r) [id] = offsetof(struct pt_regs, r)
19 
20 static unsigned int pt_regs_offset[PERF_REG_X86_MAX] = {
21 	PT_REGS_OFFSET(PERF_REG_X86_AX, ax),
22 	PT_REGS_OFFSET(PERF_REG_X86_BX, bx),
23 	PT_REGS_OFFSET(PERF_REG_X86_CX, cx),
24 	PT_REGS_OFFSET(PERF_REG_X86_DX, dx),
25 	PT_REGS_OFFSET(PERF_REG_X86_SI, si),
26 	PT_REGS_OFFSET(PERF_REG_X86_DI, di),
27 	PT_REGS_OFFSET(PERF_REG_X86_BP, bp),
28 	PT_REGS_OFFSET(PERF_REG_X86_SP, sp),
29 	PT_REGS_OFFSET(PERF_REG_X86_IP, ip),
30 	PT_REGS_OFFSET(PERF_REG_X86_FLAGS, flags),
31 	PT_REGS_OFFSET(PERF_REG_X86_CS, cs),
32 	PT_REGS_OFFSET(PERF_REG_X86_SS, ss),
33 #ifdef CONFIG_X86_32
34 	PT_REGS_OFFSET(PERF_REG_X86_DS, ds),
35 	PT_REGS_OFFSET(PERF_REG_X86_ES, es),
36 	PT_REGS_OFFSET(PERF_REG_X86_FS, fs),
37 	PT_REGS_OFFSET(PERF_REG_X86_GS, gs),
38 #else
39 	/*
40 	 * The pt_regs struct does not store
41 	 * ds, es, fs, gs in 64 bit mode.
42 	 */
43 	(unsigned int) -1,
44 	(unsigned int) -1,
45 	(unsigned int) -1,
46 	(unsigned int) -1,
47 #endif
48 #ifdef CONFIG_X86_64
49 	PT_REGS_OFFSET(PERF_REG_X86_R8, r8),
50 	PT_REGS_OFFSET(PERF_REG_X86_R9, r9),
51 	PT_REGS_OFFSET(PERF_REG_X86_R10, r10),
52 	PT_REGS_OFFSET(PERF_REG_X86_R11, r11),
53 	PT_REGS_OFFSET(PERF_REG_X86_R12, r12),
54 	PT_REGS_OFFSET(PERF_REG_X86_R13, r13),
55 	PT_REGS_OFFSET(PERF_REG_X86_R14, r14),
56 	PT_REGS_OFFSET(PERF_REG_X86_R15, r15),
57 #endif
58 };
59 
perf_reg_value(struct pt_regs * regs,int idx)60 u64 perf_reg_value(struct pt_regs *regs, int idx)
61 {
62 	struct x86_perf_regs *perf_regs;
63 
64 	if (idx >= PERF_REG_X86_XMM0 && idx < PERF_REG_X86_XMM_MAX) {
65 		perf_regs = container_of(regs, struct x86_perf_regs, regs);
66 		if (!perf_regs->xmm_regs)
67 			return 0;
68 		return perf_regs->xmm_regs[idx - PERF_REG_X86_XMM0];
69 	}
70 
71 	if (WARN_ON_ONCE(idx >= ARRAY_SIZE(pt_regs_offset)))
72 		return 0;
73 
74 	return regs_get_register(regs, pt_regs_offset[idx]);
75 }
76 
77 #define PERF_REG_X86_RESERVED	(((1ULL << PERF_REG_X86_XMM0) - 1) & \
78 				 ~((1ULL << PERF_REG_X86_MAX) - 1))
79 
80 #ifdef CONFIG_X86_32
81 #define REG_NOSUPPORT ((1ULL << PERF_REG_X86_R8) | \
82 		       (1ULL << PERF_REG_X86_R9) | \
83 		       (1ULL << PERF_REG_X86_R10) | \
84 		       (1ULL << PERF_REG_X86_R11) | \
85 		       (1ULL << PERF_REG_X86_R12) | \
86 		       (1ULL << PERF_REG_X86_R13) | \
87 		       (1ULL << PERF_REG_X86_R14) | \
88 		       (1ULL << PERF_REG_X86_R15))
89 
perf_reg_validate(u64 mask)90 int perf_reg_validate(u64 mask)
91 {
92 	if (!mask || (mask & (REG_NOSUPPORT | PERF_REG_X86_RESERVED)))
93 		return -EINVAL;
94 
95 	return 0;
96 }
97 
perf_reg_abi(struct task_struct * task)98 u64 perf_reg_abi(struct task_struct *task)
99 {
100 	return PERF_SAMPLE_REGS_ABI_32;
101 }
102 
perf_get_regs_user(struct perf_regs * regs_user,struct pt_regs * regs)103 void perf_get_regs_user(struct perf_regs *regs_user,
104 			struct pt_regs *regs)
105 {
106 	regs_user->regs = task_pt_regs(current);
107 	regs_user->abi = perf_reg_abi(current);
108 }
109 #else /* CONFIG_X86_64 */
110 #define REG_NOSUPPORT ((1ULL << PERF_REG_X86_DS) | \
111 		       (1ULL << PERF_REG_X86_ES) | \
112 		       (1ULL << PERF_REG_X86_FS) | \
113 		       (1ULL << PERF_REG_X86_GS))
114 
perf_reg_validate(u64 mask)115 int perf_reg_validate(u64 mask)
116 {
117 	if (!mask || (mask & (REG_NOSUPPORT | PERF_REG_X86_RESERVED)))
118 		return -EINVAL;
119 
120 	return 0;
121 }
122 
perf_reg_abi(struct task_struct * task)123 u64 perf_reg_abi(struct task_struct *task)
124 {
125 	if (!user_64bit_mode(task_pt_regs(task)))
126 		return PERF_SAMPLE_REGS_ABI_32;
127 	else
128 		return PERF_SAMPLE_REGS_ABI_64;
129 }
130 
131 static DEFINE_PER_CPU(struct pt_regs, nmi_user_regs);
132 
perf_get_regs_user(struct perf_regs * regs_user,struct pt_regs * regs)133 void perf_get_regs_user(struct perf_regs *regs_user,
134 			struct pt_regs *regs)
135 {
136 	struct pt_regs *regs_user_copy = this_cpu_ptr(&nmi_user_regs);
137 	struct pt_regs *user_regs = task_pt_regs(current);
138 
139 	if (!in_nmi()) {
140 		regs_user->regs = user_regs;
141 		regs_user->abi = perf_reg_abi(current);
142 		return;
143 	}
144 
145 	/*
146 	 * If we're in an NMI that interrupted task_pt_regs setup, then
147 	 * we can't sample user regs at all.  This check isn't really
148 	 * sufficient, though, as we could be in an NMI inside an interrupt
149 	 * that happened during task_pt_regs setup.
150 	 */
151 	if (regs->sp > (unsigned long)&user_regs->r11 &&
152 	    regs->sp <= (unsigned long)(user_regs + 1)) {
153 		regs_user->abi = PERF_SAMPLE_REGS_ABI_NONE;
154 		regs_user->regs = NULL;
155 		return;
156 	}
157 
158 	/*
159 	 * These registers are always saved on 64-bit syscall entry.
160 	 * On 32-bit entry points, they are saved too except r8..r11.
161 	 */
162 	regs_user_copy->ip = user_regs->ip;
163 	regs_user_copy->ax = user_regs->ax;
164 	regs_user_copy->cx = user_regs->cx;
165 	regs_user_copy->dx = user_regs->dx;
166 	regs_user_copy->si = user_regs->si;
167 	regs_user_copy->di = user_regs->di;
168 	regs_user_copy->r8 = user_regs->r8;
169 	regs_user_copy->r9 = user_regs->r9;
170 	regs_user_copy->r10 = user_regs->r10;
171 	regs_user_copy->r11 = user_regs->r11;
172 	regs_user_copy->orig_ax = user_regs->orig_ax;
173 	regs_user_copy->flags = user_regs->flags;
174 	regs_user_copy->sp = user_regs->sp;
175 	regs_user_copy->cs = user_regs->cs;
176 	regs_user_copy->ss = user_regs->ss;
177 	/*
178 	 * Store user space frame-pointer value on sample
179 	 * to facilitate stack unwinding for cases when
180 	 * user space executable code has such support
181 	 * enabled at compile time:
182 	 */
183 	regs_user_copy->bp = user_regs->bp;
184 
185 	regs_user_copy->bx = -1;
186 	regs_user_copy->r12 = -1;
187 	regs_user_copy->r13 = -1;
188 	regs_user_copy->r14 = -1;
189 	regs_user_copy->r15 = -1;
190 	/*
191 	 * For this to be at all useful, we need a reasonable guess for
192 	 * the ABI.  Be careful: we're in NMI context, and we're
193 	 * considering current to be the current task, so we should
194 	 * be careful not to look at any other percpu variables that might
195 	 * change during context switches.
196 	 */
197 	regs_user->abi = user_64bit_mode(user_regs) ?
198 		PERF_SAMPLE_REGS_ABI_64 : PERF_SAMPLE_REGS_ABI_32;
199 
200 	regs_user->regs = regs_user_copy;
201 }
202 #endif /* CONFIG_X86_32 */
203