Commit | Line | Data |
---|---|---|
1da177e4 LT |
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 | u64 *prev_pfs_loc; /* state for WAR for old spinlock ool code */ | |
33 | } ia64_backtrace_t; | |
34 | ||
35 | #if __GNUC__ < 3 || (__GNUC__ == 3 && __GNUC_MINOR__ < 3) | |
36 | /* | |
37 | * Returns non-zero if the PC is in the spinlock contention out-of-line code | |
38 | * with non-standard calling sequence (on older compilers). | |
39 | */ | |
40 | static __inline__ int in_old_ool_spinlock_code(unsigned long pc) | |
41 | { | |
42 | extern const char ia64_spinlock_contention_pre3_4[] __attribute__ ((weak)); | |
43 | extern const char ia64_spinlock_contention_pre3_4_end[] __attribute__ ((weak)); | |
44 | unsigned long sc_start = (unsigned long)ia64_spinlock_contention_pre3_4; | |
45 | unsigned long sc_end = (unsigned long)ia64_spinlock_contention_pre3_4_end; | |
46 | return (sc_start && sc_end && pc >= sc_start && pc < sc_end); | |
47 | } | |
48 | #else | |
49 | /* Newer spinlock code does a proper br.call and works fine with the unwinder */ | |
50 | #define in_old_ool_spinlock_code(pc) 0 | |
51 | #endif | |
52 | ||
53 | /* Returns non-zero if the PC is in the Interrupt Vector Table */ | |
54 | static __inline__ int in_ivt_code(unsigned long pc) | |
55 | { | |
56 | extern char ia64_ivt[]; | |
57 | return (pc >= (u_long)ia64_ivt && pc < (u_long)ia64_ivt+32768); | |
58 | } | |
59 | ||
60 | /* | |
61 | * Unwind to next stack frame. | |
62 | */ | |
63 | static __inline__ int next_frame(ia64_backtrace_t *bt) | |
64 | { | |
65 | /* | |
66 | * Avoid unsightly console message from unw_unwind() when attempting | |
67 | * to unwind through the Interrupt Vector Table which has no unwind | |
68 | * information. | |
69 | */ | |
70 | if (in_ivt_code(bt->frame.ip)) | |
71 | return 0; | |
72 | ||
73 | /* | |
74 | * WAR for spinlock contention from leaf functions. ia64_spinlock_contention_pre3_4 | |
75 | * has ar.pfs == r0. Leaf functions do not modify ar.pfs so ar.pfs remains | |
76 | * as 0, stopping the backtrace. Record the previous ar.pfs when the current | |
77 | * IP is in ia64_spinlock_contention_pre3_4 then unwind, if pfs_loc has not changed | |
78 | * after unwind then use pt_regs.ar_pfs which is where the real ar.pfs is for | |
79 | * leaf functions. | |
80 | */ | |
81 | if (bt->prev_pfs_loc && bt->regs && bt->frame.pfs_loc == bt->prev_pfs_loc) | |
82 | bt->frame.pfs_loc = &bt->regs->ar_pfs; | |
83 | bt->prev_pfs_loc = (in_old_ool_spinlock_code(bt->frame.ip) ? bt->frame.pfs_loc : NULL); | |
84 | ||
85 | return unw_unwind(&bt->frame) == 0; | |
86 | } | |
87 | ||
88 | ||
89 | static void do_ia64_backtrace(struct unw_frame_info *info, void *vdata) | |
90 | { | |
91 | ia64_backtrace_t *bt = vdata; | |
92 | struct switch_stack *sw; | |
93 | int count = 0; | |
94 | u_long pc, sp; | |
95 | ||
96 | sw = (struct switch_stack *)(info+1); | |
97 | /* padding from unw_init_running */ | |
98 | sw = (struct switch_stack *)(((unsigned long)sw + 15) & ~15); | |
99 | ||
100 | unw_init_frame_info(&bt->frame, current, sw); | |
101 | ||
102 | /* skip over interrupt frame and oprofile calls */ | |
103 | do { | |
104 | unw_get_sp(&bt->frame, &sp); | |
105 | if (sp >= (u_long)bt->regs) | |
106 | break; | |
107 | if (!next_frame(bt)) | |
108 | return; | |
109 | } while (count++ < 200); | |
110 | ||
111 | /* finally, grab the actual sample */ | |
112 | while (bt->depth-- && next_frame(bt)) { | |
113 | unw_get_ip(&bt->frame, &pc); | |
114 | oprofile_add_trace(pc); | |
115 | if (unw_is_intr_frame(&bt->frame)) { | |
116 | /* | |
117 | * Interrupt received on kernel stack; this can | |
118 | * happen when timer interrupt fires while processing | |
119 | * a softirq from the tail end of a hardware interrupt | |
120 | * which interrupted a system call. Don't laugh, it | |
121 | * happens! Splice the backtrace into two parts to | |
122 | * avoid spurious cycles in the gprof output. | |
123 | */ | |
124 | /* TODO: split rather than drop the 2nd half */ | |
125 | break; | |
126 | } | |
127 | } | |
128 | } | |
129 | ||
130 | void | |
131 | ia64_backtrace(struct pt_regs * const regs, unsigned int depth) | |
132 | { | |
133 | ia64_backtrace_t bt; | |
134 | unsigned long flags; | |
135 | ||
136 | /* | |
137 | * On IA64 there is little hope of getting backtraces from | |
138 | * user space programs -- the problems of getting the unwind | |
139 | * information from arbitrary user programs are extreme. | |
140 | */ | |
141 | if (user_mode(regs)) | |
142 | return; | |
143 | ||
144 | bt.depth = depth; | |
145 | bt.regs = regs; | |
146 | bt.prev_pfs_loc = NULL; | |
147 | local_irq_save(flags); | |
148 | unw_init_running(do_ia64_backtrace, &bt); | |
149 | local_irq_restore(flags); | |
150 | } |