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 */
 23struct 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 */
 33static struct frame_tail __user *
 34user_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
 62void
 63perf_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 */
 84static bool
 85callchain_trace(void *data, unsigned long pc)
 86{
 87	struct perf_callchain_entry_ctx *entry = data;
 88	perf_callchain_store(entry, pc);
 89	return true;
 90}
 91
 92void
 93perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 94{
 95	struct stackframe fr;
 96
 97	arm_get_current_stackframe(regs, &fr);
 98	walk_stackframe(&fr, callchain_trace, entry);
 99}
100
101unsigned long perf_instruction_pointer(struct pt_regs *regs)
102{
103	return instruction_pointer(regs);
104}
105
106unsigned long perf_misc_flags(struct pt_regs *regs)
107{
108	int misc = 0;
109
110	if (user_mode(regs))
111		misc |= PERF_RECORD_MISC_USER;
112	else
113		misc |= PERF_RECORD_MISC_KERNEL;
114
115	return misc;
116}