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Linux/arch/x86/kernel/perf_regs.c

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  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 */
196 

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