1 #include <linux/errno.h>
2 #include <linux/kernel.h>
3 #include <linux/perf_event.h>
4 #include <linux/bug.h>
5
6 #include <asm/compat.h>
7 #include <asm/perf_regs.h>
8 #include <asm/ptrace.h>
9
perf_reg_value(struct pt_regs * regs,int idx)10 u64 perf_reg_value(struct pt_regs *regs, int idx)
11 {
12 if (WARN_ON_ONCE((u32)idx >= PERF_REG_ARM64_MAX))
13 return 0;
14
15 /*
16 * Our handling of compat tasks (PERF_SAMPLE_REGS_ABI_32) is weird, but
17 * we're stuck with it for ABI compatability reasons.
18 *
19 * For a 32-bit consumer inspecting a 32-bit task, then it will look at
20 * the first 16 registers (see arch/arm/include/uapi/asm/perf_regs.h).
21 * These correspond directly to a prefix of the registers saved in our
22 * 'struct pt_regs', with the exception of the PC, so we copy that down
23 * (x15 corresponds to SP_hyp in the architecture).
24 *
25 * So far, so good.
26 *
27 * The oddity arises when a 64-bit consumer looks at a 32-bit task and
28 * asks for registers beyond PERF_REG_ARM_MAX. In this case, we return
29 * SP_usr, LR_usr and PC in the positions where the AArch64 SP, LR and
30 * PC registers would normally live. The initial idea was to allow a
31 * 64-bit unwinder to unwind a 32-bit task and, although it's not clear
32 * how well that works in practice, somebody might be relying on it.
33 *
34 * At the time we make a sample, we don't know whether the consumer is
35 * 32-bit or 64-bit, so we have to cater for both possibilities.
36 */
37 if (compat_user_mode(regs)) {
38 if ((u32)idx == PERF_REG_ARM64_SP)
39 return regs->compat_sp;
40 if ((u32)idx == PERF_REG_ARM64_LR)
41 return regs->compat_lr;
42 if (idx == 15)
43 return regs->pc;
44 }
45
46 if ((u32)idx == PERF_REG_ARM64_SP)
47 return regs->sp;
48
49 if ((u32)idx == PERF_REG_ARM64_PC)
50 return regs->pc;
51
52 return regs->regs[idx];
53 }
54
55 #define REG_RESERVED (~((1ULL << PERF_REG_ARM64_MAX) - 1))
56
perf_reg_validate(u64 mask)57 int perf_reg_validate(u64 mask)
58 {
59 if (!mask || mask & REG_RESERVED)
60 return -EINVAL;
61
62 return 0;
63 }
64
perf_reg_abi(struct task_struct * task)65 u64 perf_reg_abi(struct task_struct *task)
66 {
67 if (is_compat_thread(task_thread_info(task)))
68 return PERF_SAMPLE_REGS_ABI_32;
69 else
70 return PERF_SAMPLE_REGS_ABI_64;
71 }
72
perf_get_regs_user(struct perf_regs * regs_user,struct pt_regs * regs,struct pt_regs * regs_user_copy)73 void perf_get_regs_user(struct perf_regs *regs_user,
74 struct pt_regs *regs,
75 struct pt_regs *regs_user_copy)
76 {
77 regs_user->regs = task_pt_regs(current);
78 regs_user->abi = perf_reg_abi(current);
79 }
80