1 /*
2  * AVR32 specific backtracing code for oprofile
3  *
4  * Copyright 2008 Weinmann GmbH
5  *
6  * Author: Nikolaus Voss <n.voss@weinmann.de>
7  *
8  * Based on i386 oprofile backtrace code by John Levon and David Smith
9  *
10  * This program is free software; you can redistribute it and/or modify
11  * it under the terms of the GNU General Public License version 2 as
12  * published by the Free Software Foundation.
13  *
14  */
15 
16 #include <linux/oprofile.h>
17 #include <linux/sched.h>
18 #include <linux/uaccess.h>
19 
20 /* The first two words of each frame on the stack look like this if we have
21  * frame pointers */
22 struct frame_head {
23 	unsigned long lr;
24 	struct frame_head *fp;
25 };
26 
27 /* copied from arch/avr32/kernel/process.c */
valid_stack_ptr(struct thread_info * tinfo,unsigned long p)28 static inline int valid_stack_ptr(struct thread_info *tinfo, unsigned long p)
29 {
30 	return (p > (unsigned long)tinfo)
31 		&& (p < (unsigned long)tinfo + THREAD_SIZE - 3);
32 }
33 
34 /* copied from arch/x86/oprofile/backtrace.c */
dump_user_backtrace(struct frame_head * head)35 static struct frame_head *dump_user_backtrace(struct frame_head *head)
36 {
37 	struct frame_head bufhead[2];
38 
39 	/* Also check accessibility of one struct frame_head beyond */
40 	if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
41 		return NULL;
42 	if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
43 		return NULL;
44 
45 	oprofile_add_trace(bufhead[0].lr);
46 
47 	/* frame pointers should strictly progress back up the stack
48 	 * (towards higher addresses) */
49 	if (bufhead[0].fp <= head)
50 		return NULL;
51 
52 	return bufhead[0].fp;
53 }
54 
avr32_backtrace(struct pt_regs * const regs,unsigned int depth)55 void avr32_backtrace(struct pt_regs * const regs, unsigned int depth)
56 {
57 	/* Get first frame pointer */
58 	struct frame_head *head = (struct frame_head *)(regs->r7);
59 
60 	if (!user_mode(regs)) {
61 #ifdef CONFIG_FRAME_POINTER
62 		/*
63 		 * Traverse the kernel stack from frame to frame up to
64 		 * "depth" steps.
65 		 */
66 		while (depth-- && valid_stack_ptr(task_thread_info(current),
67 						  (unsigned long)head)) {
68 			oprofile_add_trace(head->lr);
69 			if (head->fp <= head)
70 				break;
71 			head = head->fp;
72 		}
73 #endif
74 	} else {
75 		/* Assume we have frame pointers in user mode process */
76 		while (depth-- && head)
77 			head = dump_user_backtrace(head);
78 	}
79 }
80 
81 
82