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 } 79