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