LXR linux/arch/arm64/kernel/perf

   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
  12u64 perf_reg_value(struct pt_regs *regs, int idx)
  13{
  14        if (WARN_ON_ONCE((u32)idx >= PERF_REG_ARM64_MAX))
  15                return 0;
  16
  17        /*
  18         * Our handling of compat tasks (PERF_SAMPLE_REGS_ABI_32) is weird, but
  19         * we're stuck with it for ABI compatibility reasons.
  20         *
  21         * For a 32-bit consumer inspecting a 32-bit task, then it will look at
  22         * the first 16 registers (see arch/arm/include/uapi/asm/perf_regs.h).
  23         * These correspond directly to a prefix of the registers saved in our
  24         * 'struct pt_regs', with the exception of the PC, so we copy that down
  25         * (x15 corresponds to SP_hyp in the architecture).
  26         *
  27         * So far, so good.
  28         *
  29         * The oddity arises when a 64-bit consumer looks at a 32-bit task and
  30         * asks for registers beyond PERF_REG_ARM_MAX. In this case, we return
  31         * SP_usr, LR_usr and PC in the positions where the AArch64 SP, LR and
  32         * PC registers would normally live. The initial idea was to allow a
  33         * 64-bit unwinder to unwind a 32-bit task and, although it's not clear
  34         * how well that works in practice, somebody might be relying on it.
  35         *
  36         * At the time we make a sample, we don't know whether the consumer is
  37         * 32-bit or 64-bit, so we have to cater for both possibilities.
  38         */
  39        if (compat_user_mode(regs)) {
  40                if ((u32)idx == PERF_REG_ARM64_SP)
  41                        return regs->compat_sp;
  42                if ((u32)idx == PERF_REG_ARM64_LR)
  43                        return regs->compat_lr;
  44                if (idx == 15)
  45                        return regs->pc;
  46        }
  47
  48        if ((u32)idx == PERF_REG_ARM64_SP)
  49                return regs->sp;
  50
  51        if ((u32)idx == PERF_REG_ARM64_PC)
  52                return regs->pc;
  53
  54        return regs->regs[idx];
  55}
  56
  57#define REG_RESERVED (~((1ULL << PERF_REG_ARM64_MAX) - 1))
  58
  59int perf_reg_validate(u64 mask)
  60{
  61        if (!mask || mask & REG_RESERVED)
  62                return -EINVAL;
  63
  64        return 0;
  65}
  66
  67u64 perf_reg_abi(struct task_struct *task)
  68{
  69        if (is_compat_thread(task_thread_info(task)))
  70                return PERF_SAMPLE_REGS_ABI_32;
  71        else
  72                return PERF_SAMPLE_REGS_ABI_64;
  73}
  74
  75void perf_get_regs_user(struct perf_regs *regs_user,
  76                        struct pt_regs *regs)
  77{
  78        regs_user->regs = task_pt_regs(current);
  79        regs_user->abi = perf_reg_abi(current);
  80}
  81