arch/x86/kernel/perf_regs.c

   1 #include <linux/errno.h>
   2 #include <linux/kernel.h>
   3 #include <linux/sched.h>
   4 #include <linux/perf_event.h>
   5 #include <linux/bug.h>
   6 #include <linux/stddef.h>
   7 #include <asm/perf_regs.h>
   8 #include <asm/ptrace.h>
   9
  10 #ifdef CONFIG_X86_32
  11 #define PERF_REG_X86_MAX PERF_REG_X86_32_MAX
  12 #else
  13 #define PERF_REG_X86_MAX PERF_REG_X86_64_MAX
  14 #endif
  15
  16 #define PT_REGS_OFFSET(id, r) [id] = offsetof(struct pt_regs, r)
  17
  18 static unsigned int pt_regs_offset[PERF_REG_X86_MAX] = {
  19         PT_REGS_OFFSET(PERF_REG_X86_AX, ax),
  20         PT_REGS_OFFSET(PERF_REG_X86_BX, bx),
  21         PT_REGS_OFFSET(PERF_REG_X86_CX, cx),
  22         PT_REGS_OFFSET(PERF_REG_X86_DX, dx),
  23         PT_REGS_OFFSET(PERF_REG_X86_SI, si),
  24         PT_REGS_OFFSET(PERF_REG_X86_DI, di),
  25         PT_REGS_OFFSET(PERF_REG_X86_BP, bp),
  26         PT_REGS_OFFSET(PERF_REG_X86_SP, sp),
  27         PT_REGS_OFFSET(PERF_REG_X86_IP, ip),
  28         PT_REGS_OFFSET(PERF_REG_X86_FLAGS, flags),
  29         PT_REGS_OFFSET(PERF_REG_X86_CS, cs),
  30         PT_REGS_OFFSET(PERF_REG_X86_SS, ss),
  31 #ifdef CONFIG_X86_32
  32         PT_REGS_OFFSET(PERF_REG_X86_DS, ds),
  33         PT_REGS_OFFSET(PERF_REG_X86_ES, es),
  34         PT_REGS_OFFSET(PERF_REG_X86_FS, fs),
  35         PT_REGS_OFFSET(PERF_REG_X86_GS, gs),
  36 #else
  37         /*
  38          * The pt_regs struct does not store
  39          * ds, es, fs, gs in 64 bit mode.
  40          */
  41         (unsigned int) -1,
  42         (unsigned int) -1,
  43         (unsigned int) -1,
  44         (unsigned int) -1,
  45 #endif
  46 #ifdef CONFIG_X86_64
  47         PT_REGS_OFFSET(PERF_REG_X86_R8, r8),
  48         PT_REGS_OFFSET(PERF_REG_X86_R9, r9),
  49         PT_REGS_OFFSET(PERF_REG_X86_R10, r10),
  50         PT_REGS_OFFSET(PERF_REG_X86_R11, r11),
  51         PT_REGS_OFFSET(PERF_REG_X86_R12, r12),
  52         PT_REGS_OFFSET(PERF_REG_X86_R13, r13),
  53         PT_REGS_OFFSET(PERF_REG_X86_R14, r14),
  54         PT_REGS_OFFSET(PERF_REG_X86_R15, r15),
  55 #endif
  56 };
  57
  58 u64 perf_reg_value(struct pt_regs *regs, int idx)
  59 {
  60         if (WARN_ON_ONCE(idx >= ARRAY_SIZE(pt_regs_offset)))
  61                 return 0;
  62
  63         return regs_get_register(regs, pt_regs_offset[idx]);
  64 }
  65
  66 #define REG_RESERVED (~((1ULL << PERF_REG_X86_MAX) - 1ULL))
  67
  68 #ifdef CONFIG_X86_32
  69 int perf_reg_validate(u64 mask)
  70 {
  71         if (!mask || mask & REG_RESERVED)
  72                 return -EINVAL;
  73
  74         return 0;
  75 }
  76
  77 u64 perf_reg_abi(struct task_struct *task)
  78 {
  79         return PERF_SAMPLE_REGS_ABI_32;
  80 }
  81
  82 void perf_get_regs_user(struct perf_regs *regs_user,
  83                         struct pt_regs *regs,
  84                         struct pt_regs *regs_user_copy)
  85 {
  86         regs_user->regs = task_pt_regs(current);
  87         regs_user->abi = perf_reg_abi(current);
  88 }
  89 #else /* CONFIG_X86_64 */
  90 #define REG_NOSUPPORT ((1ULL << PERF_REG_X86_DS) | \
  91                        (1ULL << PERF_REG_X86_ES) | \
  92                        (1ULL << PERF_REG_X86_FS) | \
  93                        (1ULL << PERF_REG_X86_GS))
  94
  95 int perf_reg_validate(u64 mask)
  96 {
  97         if (!mask || mask & REG_RESERVED)
  98                 return -EINVAL;
  99
 100         if (mask & REG_NOSUPPORT)
 101                 return -EINVAL;
 102
 103         return 0;
 104 }
 105
 106 u64 perf_reg_abi(struct task_struct *task)
 107 {
 108         if (test_tsk_thread_flag(task, TIF_IA32))
 109                 return PERF_SAMPLE_REGS_ABI_32;
 110         else
 111                 return PERF_SAMPLE_REGS_ABI_64;
 112 }
 113
 114 void perf_get_regs_user(struct perf_regs *regs_user,
 115                         struct pt_regs *regs,
 116                         struct pt_regs *regs_user_copy)
 117 {
 118         struct pt_regs *user_regs = task_pt_regs(current);
 119
 120         /*
 121          * If we're in an NMI that interrupted task_pt_regs setup, then
 122          * we can't sample user regs at all.  This check isn't really
 123          * sufficient, though, as we could be in an NMI inside an interrupt
 124          * that happened during task_pt_regs setup.
 125          */
 126         if (regs->sp > (unsigned long)&user_regs->r11 &&
 127             regs->sp <= (unsigned long)(user_regs + 1)) {
 128                 regs_user->abi = PERF_SAMPLE_REGS_ABI_NONE;
 129                 regs_user->regs = NULL;
 130                 return;
 131         }
 132
 133         /*
 134          * RIP, flags, and the argument registers are usually saved.
 135          * orig_ax is probably okay, too.
 136          */
 137         regs_user_copy->ip = user_regs->ip;
 138         regs_user_copy->cx = user_regs->cx;
 139         regs_user_copy->dx = user_regs->dx;
 140         regs_user_copy->si = user_regs->si;
 141         regs_user_copy->di = user_regs->di;
 142         regs_user_copy->r8 = user_regs->r8;
 143         regs_user_copy->r9 = user_regs->r9;
 144         regs_user_copy->r10 = user_regs->r10;
 145         regs_user_copy->r11 = user_regs->r11;
 146         regs_user_copy->orig_ax = user_regs->orig_ax;
 147         regs_user_copy->flags = user_regs->flags;
 148
 149         /*
 150          * Don't even try to report the "rest" regs.
 151          */
 152         regs_user_copy->bx = -1;
 153         regs_user_copy->bp = -1;
 154         regs_user_copy->r12 = -1;
 155         regs_user_copy->r13 = -1;
 156         regs_user_copy->r14 = -1;
 157         regs_user_copy->r15 = -1;
 158
 159         /*
 160          * For this to be at all useful, we need a reasonable guess for
 161          * sp and the ABI.  Be careful: we're in NMI context, and we're
 162          * considering current to be the current task, so we should
 163          * be careful not to look at any other percpu variables that might
 164          * change during context switches.
 165          */
 166         if (IS_ENABLED(CONFIG_IA32_EMULATION) &&
 167             task_thread_info(current)->status & TS_COMPAT) {
 168                 /* Easy case: we're in a compat syscall. */
 169                 regs_user->abi = PERF_SAMPLE_REGS_ABI_32;
 170                 regs_user_copy->sp = user_regs->sp;
 171                 regs_user_copy->cs = user_regs->cs;
 172                 regs_user_copy->ss = user_regs->ss;
 173         } else if (user_regs->orig_ax != -1) {
 174                 /*
 175                  * We're probably in a 64-bit syscall.
 176                  * Warning: this code is severely racy.  At least it's better
 177                  * than just blindly copying user_regs.
 178                  */
 179                 regs_user->abi = PERF_SAMPLE_REGS_ABI_64;
 180                 regs_user_copy->sp = this_cpu_read(old_rsp);
 181                 regs_user_copy->cs = __USER_CS;
 182                 regs_user_copy->ss = __USER_DS;
 183                 regs_user_copy->cx = -1;  /* usually contains garbage */
 184         } else {
 185                 /* We're probably in an interrupt or exception. */
 186                 regs_user->abi = user_64bit_mode(user_regs) ?
 187                         PERF_SAMPLE_REGS_ABI_64 : PERF_SAMPLE_REGS_ABI_32;
 188                 regs_user_copy->sp = user_regs->sp;
 189                 regs_user_copy->cs = user_regs->cs;
 190                 regs_user_copy->ss = user_regs->ss;
 191         }
 192
 193         regs_user->regs = regs_user_copy;
 194 }
 195 #endif /* CONFIG_X86_32 */