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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 */ | |
d64af918 | 16 | #include <linux/export.h> |
ce3266c0 SM |
17 | #include <linux/kallsyms.h> |
18 | #include <linux/kernel.h> | |
19 | #include <linux/sched.h> | |
68db0cf1 | 20 | #include <linux/sched/task_stack.h> |
ce3266c0 SM |
21 | #include <linux/stacktrace.h> |
22 | #include <linux/types.h> | |
23 | #include <linux/errno.h> | |
ce3266c0 SM |
24 | #include <linux/io.h> |
25 | #include <asm/sections.h> | |
26 | #include <asm/exceptions.h> | |
27 | #include <asm/unwind.h> | |
90c0d80d | 28 | #include <asm/switch_to.h> |
ce3266c0 SM |
29 | |
30 | struct stack_trace; | |
31 | ||
32 | /* | |
33 | * On Microblaze, finding the previous stack frame is a little tricky. | |
34 | * At this writing (3/2010), Microblaze does not support CONFIG_FRAME_POINTERS, | |
35 | * and even if it did, gcc (4.1.2) does not store the frame pointer at | |
36 | * a consistent offset within each frame. To determine frame size, it is | |
37 | * necessary to search for the assembly instruction that creates or reclaims | |
38 | * the frame and extract the size from it. | |
39 | * | |
40 | * Microblaze stores the stack pointer in r1, and creates a frame via | |
41 | * | |
42 | * addik r1, r1, -FRAME_SIZE | |
43 | * | |
44 | * The frame is reclaimed via | |
45 | * | |
46 | * addik r1, r1, FRAME_SIZE | |
47 | * | |
48 | * Frame creation occurs at or near the top of a function. | |
49 | * Depending on the compiler, reclaim may occur at the end, or before | |
50 | * a mid-function return. | |
51 | * | |
52 | * A stack frame is usually not created in a leaf function. | |
53 | * | |
54 | */ | |
55 | ||
56 | /** | |
57 | * get_frame_size - Extract the stack adjustment from an | |
58 | * "addik r1, r1, adjust" instruction | |
59 | * @instr : Microblaze instruction | |
60 | * | |
61 | * Return - Number of stack bytes the instruction reserves or reclaims | |
62 | */ | |
e14ebe41 | 63 | static inline long get_frame_size(unsigned long instr) |
ce3266c0 SM |
64 | { |
65 | return abs((s16)(instr & 0xFFFF)); | |
66 | } | |
67 | ||
68 | /** | |
69 | * find_frame_creation - Search backward to find the instruction that creates | |
70 | * the stack frame (hopefully, for the same function the | |
71 | * initial PC is in). | |
72 | * @pc : Program counter at which to begin the search | |
73 | * | |
74 | * Return - PC at which stack frame creation occurs | |
75 | * NULL if this cannot be found, i.e. a leaf function | |
76 | */ | |
77 | static unsigned long *find_frame_creation(unsigned long *pc) | |
78 | { | |
79 | int i; | |
80 | ||
81 | /* NOTE: Distance to search is arbitrary | |
82 | * 250 works well for most things, | |
83 | * 750 picks up things like tcp_recvmsg(), | |
84 | * 1000 needed for fat_fill_super() | |
85 | */ | |
86 | for (i = 0; i < 1000; i++, pc--) { | |
87 | unsigned long instr; | |
88 | s16 frame_size; | |
89 | ||
90 | if (!kernel_text_address((unsigned long) pc)) | |
91 | return NULL; | |
92 | ||
93 | instr = *pc; | |
94 | ||
95 | /* addik r1, r1, foo ? */ | |
96 | if ((instr & 0xFFFF0000) != 0x30210000) | |
97 | continue; /* No */ | |
98 | ||
99 | frame_size = get_frame_size(instr); | |
100 | if ((frame_size < 8) || (frame_size & 3)) { | |
101 | pr_debug(" Invalid frame size %d at 0x%p\n", | |
102 | frame_size, pc); | |
103 | return NULL; | |
104 | } | |
105 | ||
106 | pr_debug(" Found frame creation at 0x%p, size %d\n", pc, | |
107 | frame_size); | |
108 | return pc; | |
109 | } | |
110 | ||
111 | return NULL; | |
112 | } | |
113 | ||
114 | /** | |
115 | * lookup_prev_stack_frame - Find the stack frame of the previous function. | |
116 | * @fp : Frame (stack) pointer for current function | |
117 | * @pc : Program counter within current function | |
118 | * @leaf_return : r15 value within current function. If the current function | |
119 | * is a leaf, this is the caller's return address. | |
120 | * @pprev_fp : On exit, set to frame (stack) pointer for previous function | |
121 | * @pprev_pc : On exit, set to current function caller's return address | |
122 | * | |
123 | * Return - 0 on success, -EINVAL if the previous frame cannot be found | |
124 | */ | |
125 | static int lookup_prev_stack_frame(unsigned long fp, unsigned long pc, | |
126 | unsigned long leaf_return, | |
127 | unsigned long *pprev_fp, | |
128 | unsigned long *pprev_pc) | |
129 | { | |
130 | unsigned long *prologue = NULL; | |
131 | ||
132 | /* _switch_to is a special leaf function */ | |
133 | if (pc != (unsigned long) &_switch_to) | |
134 | prologue = find_frame_creation((unsigned long *)pc); | |
135 | ||
136 | if (prologue) { | |
137 | long frame_size = get_frame_size(*prologue); | |
138 | ||
139 | *pprev_fp = fp + frame_size; | |
140 | *pprev_pc = *(unsigned long *)fp; | |
141 | } else { | |
142 | if (!leaf_return) | |
143 | return -EINVAL; | |
144 | *pprev_pc = leaf_return; | |
145 | *pprev_fp = fp; | |
146 | } | |
147 | ||
148 | /* NOTE: don't check kernel_text_address here, to allow display | |
149 | * of userland return address | |
150 | */ | |
151 | return (!*pprev_pc || (*pprev_pc & 3)) ? -EINVAL : 0; | |
152 | } | |
153 | ||
154 | static void microblaze_unwind_inner(struct task_struct *task, | |
155 | unsigned long pc, unsigned long fp, | |
156 | unsigned long leaf_return, | |
157 | struct stack_trace *trace); | |
158 | ||
159 | /** | |
160 | * unwind_trap - Unwind through a system trap, that stored previous state | |
161 | * on the stack. | |
162 | */ | |
163 | #ifdef CONFIG_MMU | |
164 | static inline void unwind_trap(struct task_struct *task, unsigned long pc, | |
165 | unsigned long fp, struct stack_trace *trace) | |
166 | { | |
167 | /* To be implemented */ | |
168 | } | |
169 | #else | |
170 | static inline void unwind_trap(struct task_struct *task, unsigned long pc, | |
171 | unsigned long fp, struct stack_trace *trace) | |
172 | { | |
173 | const struct pt_regs *regs = (const struct pt_regs *) fp; | |
174 | microblaze_unwind_inner(task, regs->pc, regs->r1, regs->r15, trace); | |
175 | } | |
176 | #endif | |
177 | ||
178 | /** | |
179 | * microblaze_unwind_inner - Unwind the stack from the specified point | |
180 | * @task : Task whose stack we are to unwind (may be NULL) | |
181 | * @pc : Program counter from which we start unwinding | |
182 | * @fp : Frame (stack) pointer from which we start unwinding | |
183 | * @leaf_return : Value of r15 at pc. If the function is a leaf, this is | |
184 | * the caller's return address. | |
185 | * @trace : Where to store stack backtrace (PC values). | |
186 | * NULL == print backtrace to kernel log | |
187 | */ | |
419ef340 | 188 | static void microblaze_unwind_inner(struct task_struct *task, |
ce3266c0 SM |
189 | unsigned long pc, unsigned long fp, |
190 | unsigned long leaf_return, | |
191 | struct stack_trace *trace) | |
192 | { | |
193 | int ofs = 0; | |
194 | ||
195 | pr_debug(" Unwinding with PC=%p, FP=%p\n", (void *)pc, (void *)fp); | |
196 | if (!pc || !fp || (pc & 3) || (fp & 3)) { | |
197 | pr_debug(" Invalid state for unwind, aborting\n"); | |
198 | return; | |
199 | } | |
200 | for (; pc != 0;) { | |
201 | unsigned long next_fp, next_pc = 0; | |
202 | unsigned long return_to = pc + 2 * sizeof(unsigned long); | |
203 | const struct trap_handler_info *handler = | |
204 | µblaze_trap_handlers; | |
205 | ||
206 | /* Is previous function the HW exception handler? */ | |
207 | if ((return_to >= (unsigned long)&_hw_exception_handler) | |
208 | &&(return_to < (unsigned long)&ex_handler_unhandled)) { | |
209 | /* | |
210 | * HW exception handler doesn't save all registers, | |
211 | * so we open-code a special case of unwind_trap() | |
212 | */ | |
213 | #ifndef CONFIG_MMU | |
214 | const struct pt_regs *regs = | |
215 | (const struct pt_regs *) fp; | |
216 | #endif | |
217 | pr_info("HW EXCEPTION\n"); | |
218 | #ifndef CONFIG_MMU | |
219 | microblaze_unwind_inner(task, regs->r17 - 4, | |
220 | fp + EX_HANDLER_STACK_SIZ, | |
221 | regs->r15, trace); | |
222 | #endif | |
223 | return; | |
224 | } | |
225 | ||
226 | /* Is previous function a trap handler? */ | |
227 | for (; handler->start_addr; ++handler) { | |
228 | if ((return_to >= handler->start_addr) | |
229 | && (return_to <= handler->end_addr)) { | |
230 | if (!trace) | |
231 | pr_info("%s\n", handler->trap_name); | |
232 | unwind_trap(task, pc, fp, trace); | |
233 | return; | |
234 | } | |
235 | } | |
236 | pc -= ofs; | |
237 | ||
238 | if (trace) { | |
239 | #ifdef CONFIG_STACKTRACE | |
240 | if (trace->skip > 0) | |
241 | trace->skip--; | |
242 | else | |
243 | trace->entries[trace->nr_entries++] = pc; | |
244 | ||
245 | if (trace->nr_entries >= trace->max_entries) | |
246 | break; | |
247 | #endif | |
248 | } else { | |
249 | /* Have we reached userland? */ | |
250 | if (unlikely(pc == task_pt_regs(task)->pc)) { | |
251 | pr_info("[<%p>] PID %lu [%s]\n", | |
252 | (void *) pc, | |
253 | (unsigned long) task->pid, | |
254 | task->comm); | |
255 | break; | |
256 | } else | |
257 | print_ip_sym(pc); | |
258 | } | |
259 | ||
260 | /* Stop when we reach anything not part of the kernel */ | |
261 | if (!kernel_text_address(pc)) | |
262 | break; | |
263 | ||
264 | if (lookup_prev_stack_frame(fp, pc, leaf_return, &next_fp, | |
265 | &next_pc) == 0) { | |
266 | ofs = sizeof(unsigned long); | |
267 | pc = next_pc & ~3; | |
268 | fp = next_fp; | |
269 | leaf_return = 0; | |
270 | } else { | |
271 | pr_debug(" Failed to find previous stack frame\n"); | |
272 | break; | |
273 | } | |
274 | ||
275 | pr_debug(" Next PC=%p, next FP=%p\n", | |
276 | (void *)next_pc, (void *)next_fp); | |
277 | } | |
278 | } | |
279 | ||
280 | /** | |
281 | * microblaze_unwind - Stack unwinder for Microblaze (external entry point) | |
282 | * @task : Task whose stack we are to unwind (NULL == current) | |
283 | * @trace : Where to store stack backtrace (PC values). | |
284 | * NULL == print backtrace to kernel log | |
285 | */ | |
286 | void microblaze_unwind(struct task_struct *task, struct stack_trace *trace) | |
287 | { | |
288 | if (task) { | |
289 | if (task == current) { | |
290 | const struct pt_regs *regs = task_pt_regs(task); | |
291 | microblaze_unwind_inner(task, regs->pc, regs->r1, | |
292 | regs->r15, trace); | |
293 | } else { | |
294 | struct thread_info *thread_info = | |
295 | (struct thread_info *)(task->stack); | |
296 | const struct cpu_context *cpu_context = | |
297 | &thread_info->cpu_context; | |
298 | ||
299 | microblaze_unwind_inner(task, | |
300 | (unsigned long) &_switch_to, | |
301 | cpu_context->r1, | |
302 | cpu_context->r15, trace); | |
303 | } | |
304 | } else { | |
305 | unsigned long pc, fp; | |
306 | ||
307 | __asm__ __volatile__ ("or %0, r1, r0" : "=r" (fp)); | |
308 | ||
309 | __asm__ __volatile__ ( | |
310 | "brlid %0, 0f;" | |
311 | "nop;" | |
312 | "0:" | |
313 | : "=r" (pc) | |
314 | ); | |
315 | ||
316 | /* Since we are not a leaf function, use leaf_return = 0 */ | |
317 | microblaze_unwind_inner(current, pc, fp, 0, trace); | |
318 | } | |
319 | } | |
320 |