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ce3266c0 SM |
1 | /* |
2 | * Backtrace support for Microblaze | |
3 | * | |
4 | * Copyright (C) 2010 Digital Design Corporation | |
5 | * | |
6 | * Based on arch/sh/kernel/cpu/sh5/unwind.c code which is: | |
7 | * Copyright (C) 2004 Paul Mundt | |
8 | * Copyright (C) 2004 Richard Curnow | |
9 | * | |
10 | * This file is subject to the terms and conditions of the GNU General Public | |
11 | * License. See the file "COPYING" in the main directory of this archive | |
12 | * for more details. | |
13 | */ | |
14 | ||
15 | /* #define DEBUG 1 */ | |
16 | #include <linux/kallsyms.h> | |
17 | #include <linux/kernel.h> | |
18 | #include <linux/sched.h> | |
19 | #include <linux/stacktrace.h> | |
20 | #include <linux/types.h> | |
21 | #include <linux/errno.h> | |
22 | #include <linux/module.h> | |
23 | #include <linux/io.h> | |
24 | #include <asm/sections.h> | |
25 | #include <asm/exceptions.h> | |
26 | #include <asm/unwind.h> | |
90c0d80d | 27 | #include <asm/switch_to.h> |
ce3266c0 SM |
28 | |
29 | struct stack_trace; | |
30 | ||
31 | /* | |
32 | * On Microblaze, finding the previous stack frame is a little tricky. | |
33 | * At this writing (3/2010), Microblaze does not support CONFIG_FRAME_POINTERS, | |
34 | * and even if it did, gcc (4.1.2) does not store the frame pointer at | |
35 | * a consistent offset within each frame. To determine frame size, it is | |
36 | * necessary to search for the assembly instruction that creates or reclaims | |
37 | * the frame and extract the size from it. | |
38 | * | |
39 | * Microblaze stores the stack pointer in r1, and creates a frame via | |
40 | * | |
41 | * addik r1, r1, -FRAME_SIZE | |
42 | * | |
43 | * The frame is reclaimed via | |
44 | * | |
45 | * addik r1, r1, FRAME_SIZE | |
46 | * | |
47 | * Frame creation occurs at or near the top of a function. | |
48 | * Depending on the compiler, reclaim may occur at the end, or before | |
49 | * a mid-function return. | |
50 | * | |
51 | * A stack frame is usually not created in a leaf function. | |
52 | * | |
53 | */ | |
54 | ||
55 | /** | |
56 | * get_frame_size - Extract the stack adjustment from an | |
57 | * "addik r1, r1, adjust" instruction | |
58 | * @instr : Microblaze instruction | |
59 | * | |
60 | * Return - Number of stack bytes the instruction reserves or reclaims | |
61 | */ | |
62 | inline long get_frame_size(unsigned long instr) | |
63 | { | |
64 | return abs((s16)(instr & 0xFFFF)); | |
65 | } | |
66 | ||
67 | /** | |
68 | * find_frame_creation - Search backward to find the instruction that creates | |
69 | * the stack frame (hopefully, for the same function the | |
70 | * initial PC is in). | |
71 | * @pc : Program counter at which to begin the search | |
72 | * | |
73 | * Return - PC at which stack frame creation occurs | |
74 | * NULL if this cannot be found, i.e. a leaf function | |
75 | */ | |
76 | static unsigned long *find_frame_creation(unsigned long *pc) | |
77 | { | |
78 | int i; | |
79 | ||
80 | /* NOTE: Distance to search is arbitrary | |
81 | * 250 works well for most things, | |
82 | * 750 picks up things like tcp_recvmsg(), | |
83 | * 1000 needed for fat_fill_super() | |
84 | */ | |
85 | for (i = 0; i < 1000; i++, pc--) { | |
86 | unsigned long instr; | |
87 | s16 frame_size; | |
88 | ||
89 | if (!kernel_text_address((unsigned long) pc)) | |
90 | return NULL; | |
91 | ||
92 | instr = *pc; | |
93 | ||
94 | /* addik r1, r1, foo ? */ | |
95 | if ((instr & 0xFFFF0000) != 0x30210000) | |
96 | continue; /* No */ | |
97 | ||
98 | frame_size = get_frame_size(instr); | |
99 | if ((frame_size < 8) || (frame_size & 3)) { | |
100 | pr_debug(" Invalid frame size %d at 0x%p\n", | |
101 | frame_size, pc); | |
102 | return NULL; | |
103 | } | |
104 | ||
105 | pr_debug(" Found frame creation at 0x%p, size %d\n", pc, | |
106 | frame_size); | |
107 | return pc; | |
108 | } | |
109 | ||
110 | return NULL; | |
111 | } | |
112 | ||
113 | /** | |
114 | * lookup_prev_stack_frame - Find the stack frame of the previous function. | |
115 | * @fp : Frame (stack) pointer for current function | |
116 | * @pc : Program counter within current function | |
117 | * @leaf_return : r15 value within current function. If the current function | |
118 | * is a leaf, this is the caller's return address. | |
119 | * @pprev_fp : On exit, set to frame (stack) pointer for previous function | |
120 | * @pprev_pc : On exit, set to current function caller's return address | |
121 | * | |
122 | * Return - 0 on success, -EINVAL if the previous frame cannot be found | |
123 | */ | |
124 | static int lookup_prev_stack_frame(unsigned long fp, unsigned long pc, | |
125 | unsigned long leaf_return, | |
126 | unsigned long *pprev_fp, | |
127 | unsigned long *pprev_pc) | |
128 | { | |
129 | unsigned long *prologue = NULL; | |
130 | ||
131 | /* _switch_to is a special leaf function */ | |
132 | if (pc != (unsigned long) &_switch_to) | |
133 | prologue = find_frame_creation((unsigned long *)pc); | |
134 | ||
135 | if (prologue) { | |
136 | long frame_size = get_frame_size(*prologue); | |
137 | ||
138 | *pprev_fp = fp + frame_size; | |
139 | *pprev_pc = *(unsigned long *)fp; | |
140 | } else { | |
141 | if (!leaf_return) | |
142 | return -EINVAL; | |
143 | *pprev_pc = leaf_return; | |
144 | *pprev_fp = fp; | |
145 | } | |
146 | ||
147 | /* NOTE: don't check kernel_text_address here, to allow display | |
148 | * of userland return address | |
149 | */ | |
150 | return (!*pprev_pc || (*pprev_pc & 3)) ? -EINVAL : 0; | |
151 | } | |
152 | ||
153 | static void microblaze_unwind_inner(struct task_struct *task, | |
154 | unsigned long pc, unsigned long fp, | |
155 | unsigned long leaf_return, | |
156 | struct stack_trace *trace); | |
157 | ||
158 | /** | |
159 | * unwind_trap - Unwind through a system trap, that stored previous state | |
160 | * on the stack. | |
161 | */ | |
162 | #ifdef CONFIG_MMU | |
163 | static inline void unwind_trap(struct task_struct *task, unsigned long pc, | |
164 | unsigned long fp, struct stack_trace *trace) | |
165 | { | |
166 | /* To be implemented */ | |
167 | } | |
168 | #else | |
169 | static inline void unwind_trap(struct task_struct *task, unsigned long pc, | |
170 | unsigned long fp, struct stack_trace *trace) | |
171 | { | |
172 | const struct pt_regs *regs = (const struct pt_regs *) fp; | |
173 | microblaze_unwind_inner(task, regs->pc, regs->r1, regs->r15, trace); | |
174 | } | |
175 | #endif | |
176 | ||
177 | /** | |
178 | * microblaze_unwind_inner - Unwind the stack from the specified point | |
179 | * @task : Task whose stack we are to unwind (may be NULL) | |
180 | * @pc : Program counter from which we start unwinding | |
181 | * @fp : Frame (stack) pointer from which we start unwinding | |
182 | * @leaf_return : Value of r15 at pc. If the function is a leaf, this is | |
183 | * the caller's return address. | |
184 | * @trace : Where to store stack backtrace (PC values). | |
185 | * NULL == print backtrace to kernel log | |
186 | */ | |
419ef340 | 187 | static void microblaze_unwind_inner(struct task_struct *task, |
ce3266c0 SM |
188 | unsigned long pc, unsigned long fp, |
189 | unsigned long leaf_return, | |
190 | struct stack_trace *trace) | |
191 | { | |
192 | int ofs = 0; | |
193 | ||
194 | pr_debug(" Unwinding with PC=%p, FP=%p\n", (void *)pc, (void *)fp); | |
195 | if (!pc || !fp || (pc & 3) || (fp & 3)) { | |
196 | pr_debug(" Invalid state for unwind, aborting\n"); | |
197 | return; | |
198 | } | |
199 | for (; pc != 0;) { | |
200 | unsigned long next_fp, next_pc = 0; | |
201 | unsigned long return_to = pc + 2 * sizeof(unsigned long); | |
202 | const struct trap_handler_info *handler = | |
203 | µblaze_trap_handlers; | |
204 | ||
205 | /* Is previous function the HW exception handler? */ | |
206 | if ((return_to >= (unsigned long)&_hw_exception_handler) | |
207 | &&(return_to < (unsigned long)&ex_handler_unhandled)) { | |
208 | /* | |
209 | * HW exception handler doesn't save all registers, | |
210 | * so we open-code a special case of unwind_trap() | |
211 | */ | |
212 | #ifndef CONFIG_MMU | |
213 | const struct pt_regs *regs = | |
214 | (const struct pt_regs *) fp; | |
215 | #endif | |
216 | pr_info("HW EXCEPTION\n"); | |
217 | #ifndef CONFIG_MMU | |
218 | microblaze_unwind_inner(task, regs->r17 - 4, | |
219 | fp + EX_HANDLER_STACK_SIZ, | |
220 | regs->r15, trace); | |
221 | #endif | |
222 | return; | |
223 | } | |
224 | ||
225 | /* Is previous function a trap handler? */ | |
226 | for (; handler->start_addr; ++handler) { | |
227 | if ((return_to >= handler->start_addr) | |
228 | && (return_to <= handler->end_addr)) { | |
229 | if (!trace) | |
230 | pr_info("%s\n", handler->trap_name); | |
231 | unwind_trap(task, pc, fp, trace); | |
232 | return; | |
233 | } | |
234 | } | |
235 | pc -= ofs; | |
236 | ||
237 | if (trace) { | |
238 | #ifdef CONFIG_STACKTRACE | |
239 | if (trace->skip > 0) | |
240 | trace->skip--; | |
241 | else | |
242 | trace->entries[trace->nr_entries++] = pc; | |
243 | ||
244 | if (trace->nr_entries >= trace->max_entries) | |
245 | break; | |
246 | #endif | |
247 | } else { | |
248 | /* Have we reached userland? */ | |
249 | if (unlikely(pc == task_pt_regs(task)->pc)) { | |
250 | pr_info("[<%p>] PID %lu [%s]\n", | |
251 | (void *) pc, | |
252 | (unsigned long) task->pid, | |
253 | task->comm); | |
254 | break; | |
255 | } else | |
256 | print_ip_sym(pc); | |
257 | } | |
258 | ||
259 | /* Stop when we reach anything not part of the kernel */ | |
260 | if (!kernel_text_address(pc)) | |
261 | break; | |
262 | ||
263 | if (lookup_prev_stack_frame(fp, pc, leaf_return, &next_fp, | |
264 | &next_pc) == 0) { | |
265 | ofs = sizeof(unsigned long); | |
266 | pc = next_pc & ~3; | |
267 | fp = next_fp; | |
268 | leaf_return = 0; | |
269 | } else { | |
270 | pr_debug(" Failed to find previous stack frame\n"); | |
271 | break; | |
272 | } | |
273 | ||
274 | pr_debug(" Next PC=%p, next FP=%p\n", | |
275 | (void *)next_pc, (void *)next_fp); | |
276 | } | |
277 | } | |
278 | ||
279 | /** | |
280 | * microblaze_unwind - Stack unwinder for Microblaze (external entry point) | |
281 | * @task : Task whose stack we are to unwind (NULL == current) | |
282 | * @trace : Where to store stack backtrace (PC values). | |
283 | * NULL == print backtrace to kernel log | |
284 | */ | |
285 | void microblaze_unwind(struct task_struct *task, struct stack_trace *trace) | |
286 | { | |
287 | if (task) { | |
288 | if (task == current) { | |
289 | const struct pt_regs *regs = task_pt_regs(task); | |
290 | microblaze_unwind_inner(task, regs->pc, regs->r1, | |
291 | regs->r15, trace); | |
292 | } else { | |
293 | struct thread_info *thread_info = | |
294 | (struct thread_info *)(task->stack); | |
295 | const struct cpu_context *cpu_context = | |
296 | &thread_info->cpu_context; | |
297 | ||
298 | microblaze_unwind_inner(task, | |
299 | (unsigned long) &_switch_to, | |
300 | cpu_context->r1, | |
301 | cpu_context->r15, trace); | |
302 | } | |
303 | } else { | |
304 | unsigned long pc, fp; | |
305 | ||
306 | __asm__ __volatile__ ("or %0, r1, r0" : "=r" (fp)); | |
307 | ||
308 | __asm__ __volatile__ ( | |
309 | "brlid %0, 0f;" | |
310 | "nop;" | |
311 | "0:" | |
312 | : "=r" (pc) | |
313 | ); | |
314 | ||
315 | /* Since we are not a leaf function, use leaf_return = 0 */ | |
316 | microblaze_unwind_inner(current, pc, fp, 0, trace); | |
317 | } | |
318 | } | |
319 |