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Linux/arch/x86/kernel/perf_regs.c

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  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 
 60 u64 perf_reg_value(struct pt_regs *regs, int idx)
 61 {
 62         if (WARN_ON_ONCE(idx >= ARRAY_SIZE(pt_regs_offset)))
 63                 return 0;
 64 
 65         return regs_get_register(regs, pt_regs_offset[idx]);
 66 }
 67 
 68 #define REG_RESERVED (~((1ULL << PERF_REG_X86_MAX) - 1ULL))
 69 
 70 #ifdef CONFIG_X86_32
 71 int perf_reg_validate(u64 mask)
 72 {
 73         if (!mask || mask & REG_RESERVED)
 74                 return -EINVAL;
 75 
 76         return 0;
 77 }
 78 
 79 u64 perf_reg_abi(struct task_struct *task)
 80 {
 81         return PERF_SAMPLE_REGS_ABI_32;
 82 }
 83 
 84 void perf_get_regs_user(struct perf_regs *regs_user,
 85                         struct pt_regs *regs,
 86                         struct pt_regs *regs_user_copy)
 87 {
 88         regs_user->regs = task_pt_regs(current);
 89         regs_user->abi = perf_reg_abi(current);
 90 }
 91 #else /* CONFIG_X86_64 */
 92 #define REG_NOSUPPORT ((1ULL << PERF_REG_X86_DS) | \
 93                        (1ULL << PERF_REG_X86_ES) | \
 94                        (1ULL << PERF_REG_X86_FS) | \
 95                        (1ULL << PERF_REG_X86_GS))
 96 
 97 int perf_reg_validate(u64 mask)
 98 {
 99         if (!mask || mask & REG_RESERVED)
100                 return -EINVAL;
101 
102         if (mask & REG_NOSUPPORT)
103                 return -EINVAL;
104 
105         return 0;
106 }
107 
108 u64 perf_reg_abi(struct task_struct *task)
109 {
110         if (test_tsk_thread_flag(task, TIF_IA32))
111                 return PERF_SAMPLE_REGS_ABI_32;
112         else
113                 return PERF_SAMPLE_REGS_ABI_64;
114 }
115 
116 void perf_get_regs_user(struct perf_regs *regs_user,
117                         struct pt_regs *regs,
118                         struct pt_regs *regs_user_copy)
119 {
120         struct pt_regs *user_regs = task_pt_regs(current);
121 
122         /*
123          * If we're in an NMI that interrupted task_pt_regs setup, then
124          * we can't sample user regs at all.  This check isn't really
125          * sufficient, though, as we could be in an NMI inside an interrupt
126          * that happened during task_pt_regs setup.
127          */
128         if (regs->sp > (unsigned long)&user_regs->r11 &&
129             regs->sp <= (unsigned long)(user_regs + 1)) {
130                 regs_user->abi = PERF_SAMPLE_REGS_ABI_NONE;
131                 regs_user->regs = NULL;
132                 return;
133         }
134 
135         /*
136          * These registers are always saved on 64-bit syscall entry.
137          * On 32-bit entry points, they are saved too except r8..r11.
138          */
139         regs_user_copy->ip = user_regs->ip;
140         regs_user_copy->ax = user_regs->ax;
141         regs_user_copy->cx = user_regs->cx;
142         regs_user_copy->dx = user_regs->dx;
143         regs_user_copy->si = user_regs->si;
144         regs_user_copy->di = user_regs->di;
145         regs_user_copy->r8 = user_regs->r8;
146         regs_user_copy->r9 = user_regs->r9;
147         regs_user_copy->r10 = user_regs->r10;
148         regs_user_copy->r11 = user_regs->r11;
149         regs_user_copy->orig_ax = user_regs->orig_ax;
150         regs_user_copy->flags = user_regs->flags;
151         regs_user_copy->sp = user_regs->sp;
152         regs_user_copy->cs = user_regs->cs;
153         regs_user_copy->ss = user_regs->ss;
154         /*
155          * Store user space frame-pointer value on sample
156          * to facilitate stack unwinding for cases when
157          * user space executable code has such support
158          * enabled at compile time:
159          */
160         regs_user_copy->bp = user_regs->bp;
161 
162         regs_user_copy->bx = -1;
163         regs_user_copy->r12 = -1;
164         regs_user_copy->r13 = -1;
165         regs_user_copy->r14 = -1;
166         regs_user_copy->r15 = -1;
167         /*
168          * For this to be at all useful, we need a reasonable guess for
169          * the ABI.  Be careful: we're in NMI context, and we're
170          * considering current to be the current task, so we should
171          * be careful not to look at any other percpu variables that might
172          * change during context switches.
173          */
174         regs_user->abi = user_64bit_mode(user_regs) ?
175                 PERF_SAMPLE_REGS_ABI_64 : PERF_SAMPLE_REGS_ABI_32;
176 
177         regs_user->regs = regs_user_copy;
178 }
179 #endif /* CONFIG_X86_32 */
180 

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