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 lr; 11 }; 12 13 static 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 35 static 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 */ 47 static 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 *user_frame_tail = (unsigned long __user *)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 */ 86 void 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 } 105 106 void 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