1 /**
2 * @file backtrace.c
3 *
4 * @remark Copyright 2004 Silicon Graphics Inc. All Rights Reserved.
5 * @remark Read the file COPYING
6 *
7 * @author Greg Banks <gnb@melbourne.sgi.com>
8 * @author Keith Owens <kaos@melbourne.sgi.com>
9 * Based on work done for the ia64 port of the SGI kernprof patch, which is
10 * Copyright (c) 2003-2004 Silicon Graphics Inc. All Rights Reserved.
11 */
12
13 #include <linux/oprofile.h>
14 #include <linux/sched.h>
15 #include <linux/mm.h>
16 #include <asm/ptrace.h>
17 #include <asm/system.h>
18
19 /*
20 * For IA64 we need to perform a complex little dance to get both
21 * the struct pt_regs and a synthetic struct switch_stack in place
22 * to allow the unwind code to work. This dance requires our unwind
23 * using code to be called from a function called from unw_init_running().
24 * There we only get a single void* data pointer, so use this struct
25 * to hold all the data we need during the unwind.
26 */
27 typedef struct
28 {
29 unsigned int depth;
30 struct pt_regs *regs;
31 struct unw_frame_info frame;
32 unsigned long *prev_pfs_loc; /* state for WAR for old spinlock ool code */
33 } ia64_backtrace_t;
34
35 /* Returns non-zero if the PC is in the Interrupt Vector Table */
in_ivt_code(unsigned long pc)36 static __inline__ int in_ivt_code(unsigned long pc)
37 {
38 extern char ia64_ivt[];
39 return (pc >= (u_long)ia64_ivt && pc < (u_long)ia64_ivt+32768);
40 }
41
42 /*
43 * Unwind to next stack frame.
44 */
next_frame(ia64_backtrace_t * bt)45 static __inline__ int next_frame(ia64_backtrace_t *bt)
46 {
47 /*
48 * Avoid unsightly console message from unw_unwind() when attempting
49 * to unwind through the Interrupt Vector Table which has no unwind
50 * information.
51 */
52 if (in_ivt_code(bt->frame.ip))
53 return 0;
54
55 /*
56 * WAR for spinlock contention from leaf functions. ia64_spinlock_contention_pre3_4
57 * has ar.pfs == r0. Leaf functions do not modify ar.pfs so ar.pfs remains
58 * as 0, stopping the backtrace. Record the previous ar.pfs when the current
59 * IP is in ia64_spinlock_contention_pre3_4 then unwind, if pfs_loc has not changed
60 * after unwind then use pt_regs.ar_pfs which is where the real ar.pfs is for
61 * leaf functions.
62 */
63 if (bt->prev_pfs_loc && bt->regs && bt->frame.pfs_loc == bt->prev_pfs_loc)
64 bt->frame.pfs_loc = &bt->regs->ar_pfs;
65 bt->prev_pfs_loc = NULL;
66
67 return unw_unwind(&bt->frame) == 0;
68 }
69
70
do_ia64_backtrace(struct unw_frame_info * info,void * vdata)71 static void do_ia64_backtrace(struct unw_frame_info *info, void *vdata)
72 {
73 ia64_backtrace_t *bt = vdata;
74 struct switch_stack *sw;
75 int count = 0;
76 u_long pc, sp;
77
78 sw = (struct switch_stack *)(info+1);
79 /* padding from unw_init_running */
80 sw = (struct switch_stack *)(((unsigned long)sw + 15) & ~15);
81
82 unw_init_frame_info(&bt->frame, current, sw);
83
84 /* skip over interrupt frame and oprofile calls */
85 do {
86 unw_get_sp(&bt->frame, &sp);
87 if (sp >= (u_long)bt->regs)
88 break;
89 if (!next_frame(bt))
90 return;
91 } while (count++ < 200);
92
93 /* finally, grab the actual sample */
94 while (bt->depth-- && next_frame(bt)) {
95 unw_get_ip(&bt->frame, &pc);
96 oprofile_add_trace(pc);
97 if (unw_is_intr_frame(&bt->frame)) {
98 /*
99 * Interrupt received on kernel stack; this can
100 * happen when timer interrupt fires while processing
101 * a softirq from the tail end of a hardware interrupt
102 * which interrupted a system call. Don't laugh, it
103 * happens! Splice the backtrace into two parts to
104 * avoid spurious cycles in the gprof output.
105 */
106 /* TODO: split rather than drop the 2nd half */
107 break;
108 }
109 }
110 }
111
112 void
ia64_backtrace(struct pt_regs * const regs,unsigned int depth)113 ia64_backtrace(struct pt_regs * const regs, unsigned int depth)
114 {
115 ia64_backtrace_t bt;
116 unsigned long flags;
117
118 /*
119 * On IA64 there is little hope of getting backtraces from
120 * user space programs -- the problems of getting the unwind
121 * information from arbitrary user programs are extreme.
122 */
123 if (user_mode(regs))
124 return;
125
126 bt.depth = depth;
127 bt.regs = regs;
128 bt.prev_pfs_loc = NULL;
129 local_irq_save(flags);
130 unw_init_running(do_ia64_backtrace, &bt);
131 local_irq_restore(flags);
132 }
133