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 /* Kernel callchain */
   8 struct stackframe {
   9         unsigned long fp;
  10         unsigned long ra;
  11 };
  12
  13 /*
  14  * Get the return address for a single stackframe and return a pointer to the
  15  * next frame tail.
  16  */
  17 static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
  18                                     unsigned long fp, unsigned long reg_ra)
  19 {
  20         struct stackframe buftail;
  21         unsigned long ra = 0;
  22         unsigned long *user_frame_tail =
  23                         (unsigned long *)(fp - sizeof(struct stackframe));
  24
  25         /* Check accessibility of one struct frame_tail beyond */
  26         if (!access_ok(user_frame_tail, sizeof(buftail)))
  27                 return 0;
  28         if (__copy_from_user_inatomic(&buftail, user_frame_tail,
  29                                       sizeof(buftail)))
  30                 return 0;
  31
  32         if (reg_ra != 0)
  33                 ra = reg_ra;
  34         else
  35                 ra = buftail.ra;
  36
  37         fp = buftail.fp;
  38         if (ra != 0)
  39                 perf_callchain_store(entry, ra);
  40         else
  41                 return 0;
  42
  43         return fp;
  44 }
  45
  46 /*
  47  * This will be called when the target is in user mode
  48  * This function will only be called when we use
  49  * "PERF_SAMPLE_CALLCHAIN" in
  50  * kernel/events/core.c:perf_prepare_sample()
  51  *
  52  * How to trigger perf_callchain_[user/kernel] :
  53  * $ perf record -e cpu-clock --call-graph fp ./program
  54  * $ perf report --call-graph
  55  *
  56  * On RISC-V platform, the program being sampled and the C library
  57  * need to be compiled with -fno-omit-frame-pointer, otherwise
  58  * the user stack will not contain function frame.
  59  */
  60 void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
  61                          struct pt_regs *regs)
  62 {
  63         struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
  64         unsigned long fp = 0;
  65
  66         /* RISC-V does not support perf in guest mode. */
  67         if (guest_cbs && guest_cbs->is_in_guest())
  68                 return;
  69
  70         fp = regs->s0;
  71         perf_callchain_store(entry, regs->sepc);
  72
  73         fp = user_backtrace(entry, fp, regs->ra);
  74         while (fp && !(fp & 0x3) && entry->nr < entry->max_stack)
  75                 fp = user_backtrace(entry, fp, 0);
  76 }
  77
  78 bool fill_callchain(unsigned long pc, void *entry)
  79 {
  80         return perf_callchain_store(entry, pc) == 0;
  81 }
  82
  83 void notrace walk_stackframe(struct task_struct *task,
  84         struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg);
  85 void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
  86                            struct pt_regs *regs)
  87 {
  88         struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
  89
  90         /* RISC-V does not support perf in guest mode. */
  91         if (guest_cbs && guest_cbs->is_in_guest()) {
  92                 pr_warn("RISC-V does not support perf in guest mode!");
  93                 return;
  94         }
  95
  96         walk_stackframe(NULL, regs, fill_callchain, entry);
  97 }