1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * ARM callchain support 4 * 5 * Copyright (C) 2009 picoChip Designs, Ltd., Jamie Iles 6 * Copyright (C) 2010 ARM Ltd., Will Deacon <will.deacon@arm.com> 7 * 8 * This code is based on the ARM OProfile backtrace code. 9 */ 10 #include <linux/perf_event.h> 11 #include <linux/uaccess.h> 12 13 #include <asm/stacktrace.h> 14 15 /* 16 * The registers we're interested in are at the end of the variable 17 * length saved register structure. The fp points at the end of this 18 * structure so the address of this struct is: 19 * (struct frame_tail *)(xxx->fp)-1 20 * 21 * This code has been adapted from the ARM OProfile support. 22 */ 23 struct frame_tail { 24 struct frame_tail __user *fp; 25 unsigned long sp; 26 unsigned long lr; 27 } __attribute__((packed)); 28 29 /* 30 * Get the return address for a single stackframe and return a pointer to the 31 * next frame tail. 32 */ 33 static struct frame_tail __user * 34 user_backtrace(struct frame_tail __user *tail, 35 struct perf_callchain_entry_ctx *entry) 36 { 37 struct frame_tail buftail; 38 unsigned long err; 39 40 if (!access_ok(tail, sizeof(buftail))) 41 return NULL; 42 43 pagefault_disable(); 44 err = __copy_from_user_inatomic(&buftail, tail, sizeof(buftail)); 45 pagefault_enable(); 46 47 if (err) 48 return NULL; 49 50 perf_callchain_store(entry, buftail.lr); 51 52 /* 53 * Frame pointers should strictly progress back up the stack 54 * (towards higher addresses). 55 */ 56 if (tail + 1 >= buftail.fp) 57 return NULL; 58 59 return buftail.fp - 1; 60 } 61 62 void 63 perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs) 64 { 65 struct frame_tail __user *tail; 66 67 perf_callchain_store(entry, regs->ARM_pc); 68 69 if (!current->mm) 70 return; 71 72 tail = (struct frame_tail __user *)regs->ARM_fp - 1; 73 74 while ((entry->nr < entry->max_stack) && 75 tail && !((unsigned long)tail & 0x3)) 76 tail = user_backtrace(tail, entry); 77 } 78 79 /* 80 * Gets called by walk_stackframe() for every stackframe. This will be called 81 * whist unwinding the stackframe and is like a subroutine return so we use 82 * the PC. 83 */ 84 static int 85 callchain_trace(struct stackframe *fr, 86 void *data) 87 { 88 struct perf_callchain_entry_ctx *entry = data; 89 perf_callchain_store(entry, fr->pc); 90 return 0; 91 } 92 93 void 94 perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs) 95 { 96 struct stackframe fr; 97 98 arm_get_current_stackframe(regs, &fr); 99 walk_stackframe(&fr, callchain_trace, entry); 100 } 101 102 unsigned long perf_instruction_pointer(struct pt_regs *regs) 103 { 104 return instruction_pointer(regs); 105 } 106 107 unsigned long perf_misc_flags(struct pt_regs *regs) 108 { 109 int misc = 0; 110 111 if (user_mode(regs)) 112 misc |= PERF_RECORD_MISC_USER; 113 else 114 misc |= PERF_RECORD_MISC_KERNEL; 115 116 return misc; 117 } 118