LXR linux/arch/csky/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/* Kernel callchain */
   8struct stackframe {
   9        unsigned long fp;
  10        unsigned long lr;
  11};
  12
  13static int unwind_frame_kernel(struct stackframe *frame)
  14{
  15        unsigned long low = (unsigned long)task_stack_page(current);
  16        unsigned long high = low + THREAD_SIZE;
  17
  18        if (unlikely(frame->fp < low || frame->fp > high))
  19                return -EPERM;
  20
  21        if (kstack_end((void *)frame->fp) || frame->fp & 0x3)
  22                return -EPERM;
  23
  24        *frame = *(struct stackframe *)frame->fp;
  25
  26        if (__kernel_text_address(frame->lr)) {
  27                int graph = 0;
  28
  29                frame->lr = ftrace_graph_ret_addr(NULL, &graph, frame->lr,
  30                                NULL);
  31        }
  32        return 0;
  33}
  34
  35static void notrace walk_stackframe(struct stackframe *fr,
  36                        struct perf_callchain_entry_ctx *entry)
  37{
  38        do {
  39                perf_callchain_store(entry, fr->lr);
  40        } while (unwind_frame_kernel(fr) >= 0);
  41}
  42
  43/*
  44 * Get the return address for a single stackframe and return a pointer to the
  45 * next frame tail.
  46 */
  47static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
  48                        unsigned long fp, unsigned long reg_lr)
  49{
  50        struct stackframe buftail;
  51        unsigned long lr = 0;
  52        unsigned long *user_frame_tail = (unsigned long *)fp;
  53
  54        /* Check accessibility of one struct frame_tail beyond */
  55        if (!access_ok(user_frame_tail, sizeof(buftail)))
  56                return 0;
  57        if (__copy_from_user_inatomic(&buftail, user_frame_tail,
  58                                      sizeof(buftail)))
  59                return 0;
  60
  61        if (reg_lr != 0)
  62                lr = reg_lr;
  63        else
  64                lr = buftail.lr;
  65
  66        fp = buftail.fp;
  67        perf_callchain_store(entry, lr);
  68
  69        return fp;
  70}
  71
  72/*
  73 * This will be called when the target is in user mode
  74 * This function will only be called when we use
  75 * "PERF_SAMPLE_CALLCHAIN" in
  76 * kernel/events/core.c:perf_prepare_sample()
  77 *
  78 * How to trigger perf_callchain_[user/kernel] :
  79 * $ perf record -e cpu-clock --call-graph fp ./program
  80 * $ perf report --call-graph
  81 *
  82 * On C-SKY platform, the program being sampled and the C library
  83 * need to be compiled with * -mbacktrace, otherwise the user
  84 * stack will not contain function frame.
  85 */
  86void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
  87                         struct pt_regs *regs)
  88{
  89        unsigned long fp = 0;
  90
  91        fp = regs->regs[4];
  92        perf_callchain_store(entry, regs->pc);
  93
  94        /*
  95         * While backtrace from leaf function, lr is normally
  96         * not saved inside frame on C-SKY, so get lr from pt_regs
  97         * at the sample point. However, lr value can be incorrect if
  98         * lr is used as temp register
  99         */
 100        fp = user_backtrace(entry, fp, regs->lr);
 101
 102        while (fp && !(fp & 0x3) && entry->nr < entry->max_stack)
 103                fp = user_backtrace(entry, fp, 0);
 104}
 105
 106void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
 107                           struct pt_regs *regs)
 108{
 109        struct stackframe fr;
 110
 111        fr.fp = regs->regs[4];
 112        fr.lr = regs->lr;
 113        walk_stackframe(&fr, entry);
 114}
 115