1// SPDX-License-Identifier: GPL-2.0
2#include <linux/compat.h>
3#include <linux/errno.h>
4#include <linux/kernel.h>
5#include <linux/perf_event.h>
6#include <linux/bug.h>
7#include <linux/sched/task_stack.h>
8
9#include <asm/perf_regs.h>
10#include <asm/ptrace.h>
11
12static u64 perf_ext_regs_value(int idx)
13{
14 switch (idx) {
15 case PERF_REG_ARM64_VG:
16 if (WARN_ON_ONCE(!system_supports_sve()))
17 return 0;
18
19 /*
20 * Vector granule is current length in bits of SVE registers
21 * divided by 64.
22 */
23 return (task_get_sve_vl(current) * 8) / 64;
24 default:
25 WARN_ON_ONCE(true);
26 return 0;
27 }
28}
29
30u64 perf_reg_value(struct pt_regs *regs, int idx)
31{
32 if (WARN_ON_ONCE((u32)idx >= PERF_REG_ARM64_EXTENDED_MAX))
33 return 0;
34
35 /*
36 * Our handling of compat tasks (PERF_SAMPLE_REGS_ABI_32) is weird, but
37 * we're stuck with it for ABI compatibility reasons.
38 *
39 * For a 32-bit consumer inspecting a 32-bit task, then it will look at
40 * the first 16 registers (see arch/arm/include/uapi/asm/perf_regs.h).
41 * These correspond directly to a prefix of the registers saved in our
42 * 'struct pt_regs', with the exception of the PC, so we copy that down
43 * (x15 corresponds to SP_hyp in the architecture).
44 *
45 * So far, so good.
46 *
47 * The oddity arises when a 64-bit consumer looks at a 32-bit task and
48 * asks for registers beyond PERF_REG_ARM_MAX. In this case, we return
49 * SP_usr, LR_usr and PC in the positions where the AArch64 SP, LR and
50 * PC registers would normally live. The initial idea was to allow a
51 * 64-bit unwinder to unwind a 32-bit task and, although it's not clear
52 * how well that works in practice, somebody might be relying on it.
53 *
54 * At the time we make a sample, we don't know whether the consumer is
55 * 32-bit or 64-bit, so we have to cater for both possibilities.
56 */
57 if (compat_user_mode(regs)) {
58 if ((u32)idx == PERF_REG_ARM64_SP)
59 return regs->compat_sp;
60 if ((u32)idx == PERF_REG_ARM64_LR)
61 return regs->compat_lr;
62 if (idx == 15)
63 return regs->pc;
64 }
65
66 if ((u32)idx == PERF_REG_ARM64_SP)
67 return regs->sp;
68
69 if ((u32)idx == PERF_REG_ARM64_PC)
70 return regs->pc;
71
72 if ((u32)idx >= PERF_REG_ARM64_MAX)
73 return perf_ext_regs_value(idx);
74
75 return regs->regs[idx];
76}
77
78#define REG_RESERVED (~((1ULL << PERF_REG_ARM64_MAX) - 1))
79
80int perf_reg_validate(u64 mask)
81{
82 u64 reserved_mask = REG_RESERVED;
83
84 if (system_supports_sve())
85 reserved_mask &= ~(1ULL << PERF_REG_ARM64_VG);
86
87 if (!mask || mask & reserved_mask)
88 return -EINVAL;
89
90 return 0;
91}
92
93u64 perf_reg_abi(struct task_struct *task)
94{
95 if (is_compat_thread(task_thread_info(task)))
96 return PERF_SAMPLE_REGS_ABI_32;
97 else
98 return PERF_SAMPLE_REGS_ABI_64;
99}
100
101void perf_get_regs_user(struct perf_regs *regs_user,
102 struct pt_regs *regs)
103{
104 regs_user->regs = task_pt_regs(current);
105 regs_user->abi = perf_reg_abi(current);
106}
107

source code of linux/arch/arm64/kernel/perf_regs.c