arch/riscv/kernel/perf_callchain.c

   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  */
  13 static 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 *user_frame_tail =
  19                 (unsigned long __user *)(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  */
  56 void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
  57                          struct pt_regs *regs)
  58 {
  59         unsigned long fp = 0;
  60
  61         fp = regs->s0;
  62         perf_callchain_store(entry, regs->epc);
  63
  64         fp = user_backtrace(entry, fp, regs->ra);
  65         while (fp && !(fp & 0x3) && entry->nr < entry->max_stack)
  66                 fp = user_backtrace(entry, fp, 0);
  67 }
  68
  69 static bool fill_callchain(void *entry, unsigned long pc)
  70 {
  71         return perf_callchain_store(entry, pc) == 0;
  72 }
  73
  74 void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
  75                            struct pt_regs *regs)
  76 {
  77         walk_stackframe(NULL, regs, fill_callchain, entry);
  78 }