arch/x86/kernel/perf_regs.c

   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         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
  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
  98 u64 perf_reg_abi(struct task_struct *task)
  99 {
 100         return PERF_SAMPLE_REGS_ABI_32;
 101 }
 102
 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
 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
 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
 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 */