LXR linux/arch/riscv/kernel/perf

   1// SPDX-License-Identifier: GPL-2.0
   2/* Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd. */
   3
   4#include <linux/perf_event.h>
   5#include <linux/uaccess.h>
   6
   7#include <asm/stacktrace.h>
   8
   9/*
  10 * Get the return address for a single stackframe and return a pointer to the
  11 * next frame tail.
  12 */
  13static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
  14                                    unsigned long fp, unsigned long reg_ra)
  15{
  16        struct stackframe buftail;
  17        unsigned long ra = 0;
  18        unsigned long *user_frame_tail =
  19                        (unsigned long *)(fp - sizeof(struct stackframe));
  20
  21        /* Check accessibility of one struct frame_tail beyond */
  22        if (!access_ok(user_frame_tail, sizeof(buftail)))
  23                return 0;
  24        if (__copy_from_user_inatomic(&buftail, user_frame_tail,
  25                                      sizeof(buftail)))
  26                return 0;
  27
  28        if (reg_ra != 0)
  29                ra = reg_ra;
  30        else
  31                ra = buftail.ra;
  32
  33        fp = buftail.fp;
  34        if (ra != 0)
  35                perf_callchain_store(entry, ra);
  36        else
  37                return 0;
  38
  39        return fp;
  40}
  41
  42/*
  43 * This will be called when the target is in user mode
  44 * This function will only be called when we use
  45 * "PERF_SAMPLE_CALLCHAIN" in
  46 * kernel/events/core.c:perf_prepare_sample()
  47 *
  48 * How to trigger perf_callchain_[user/kernel] :
  49 * $ perf record -e cpu-clock --call-graph fp ./program
  50 * $ perf report --call-graph
  51 *
  52 * On RISC-V platform, the program being sampled and the C library
  53 * need to be compiled with -fno-omit-frame-pointer, otherwise
  54 * the user stack will not contain function frame.
  55 */
  56void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
  57                         struct pt_regs *regs)
  58{
  59        unsigned long fp = 0;
  60
  61        /* RISC-V does not support perf in guest mode. */
  62        if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
  63                return;
  64
  65        fp = regs->s0;
  66        perf_callchain_store(entry, regs->epc);
  67
  68        fp = user_backtrace(entry, fp, regs->ra);
  69        while (fp && !(fp & 0x3) && entry->nr < entry->max_stack)
  70                fp = user_backtrace(entry, fp, 0);
  71}
  72
  73static bool fill_callchain(void *entry, unsigned long pc)
  74{
  75        return perf_callchain_store(entry, pc);
  76}
  77
  78void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
  79                           struct pt_regs *regs)
  80{
  81        /* RISC-V does not support perf in guest mode. */
  82        if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
  83                pr_warn("RISC-V does not support perf in guest mode!");
  84                return;
  85        }
  86
  87        walk_stackframe(NULL, regs, fill_callchain, entry);
  88}
  89