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/export.h> |
17 | #include <linux/kallsyms.h> |
18 | #include <linux/kernel.h> |
19 | #include <linux/sched.h> |
20 | #include <linux/sched/task_stack.h> |
21 | #include <linux/stacktrace.h> |
22 | #include <linux/types.h> |
23 | #include <linux/errno.h> |
24 | #include <linux/io.h> |
25 | #include <asm/sections.h> |
26 | #include <asm/exceptions.h> |
27 | #include <asm/unwind.h> |
28 | #include <asm/switch_to.h> |
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 | */ |
63 | static inline long get_frame_size(unsigned long instr) |
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(addr: (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(pc: (unsigned long *)pc); |
135 | |
136 | if (prologue) { |
137 | long frame_size = get_frame_size(instr: *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 | const char *loglvl); |
159 | |
160 | /** |
161 | * unwind_trap - Unwind through a system trap, that stored previous state |
162 | * on the stack. |
163 | */ |
164 | static inline void unwind_trap(struct task_struct *task, unsigned long pc, |
165 | unsigned long fp, struct stack_trace *trace, |
166 | const char *loglvl) |
167 | { |
168 | /* To be implemented */ |
169 | } |
170 | |
171 | /** |
172 | * microblaze_unwind_inner - Unwind the stack from the specified point |
173 | * @task : Task whose stack we are to unwind (may be NULL) |
174 | * @pc : Program counter from which we start unwinding |
175 | * @fp : Frame (stack) pointer from which we start unwinding |
176 | * @leaf_return : Value of r15 at pc. If the function is a leaf, this is |
177 | * the caller's return address. |
178 | * @trace : Where to store stack backtrace (PC values). |
179 | * NULL == print backtrace to kernel log |
180 | * @loglvl : Used for printk log level if (trace == NULL). |
181 | */ |
182 | static void microblaze_unwind_inner(struct task_struct *task, |
183 | unsigned long pc, unsigned long fp, |
184 | unsigned long leaf_return, |
185 | struct stack_trace *trace, |
186 | const char *loglvl) |
187 | { |
188 | int ofs = 0; |
189 | |
190 | pr_debug(" Unwinding with PC=%p, FP=%p\n" , (void *)pc, (void *)fp); |
191 | if (!pc || !fp || (pc & 3) || (fp & 3)) { |
192 | pr_debug(" Invalid state for unwind, aborting\n" ); |
193 | return; |
194 | } |
195 | for (; pc != 0;) { |
196 | unsigned long next_fp, next_pc = 0; |
197 | unsigned long return_to = pc + 2 * sizeof(unsigned long); |
198 | const struct trap_handler_info *handler = |
199 | µblaze_trap_handlers; |
200 | |
201 | /* Is previous function the HW exception handler? */ |
202 | if ((return_to >= (unsigned long)&_hw_exception_handler) |
203 | &&(return_to < (unsigned long)&ex_handler_unhandled)) { |
204 | /* |
205 | * HW exception handler doesn't save all registers, |
206 | * so we open-code a special case of unwind_trap() |
207 | */ |
208 | printk("%sHW EXCEPTION\n" , loglvl); |
209 | return; |
210 | } |
211 | |
212 | /* Is previous function a trap handler? */ |
213 | for (; handler->start_addr; ++handler) { |
214 | if ((return_to >= handler->start_addr) |
215 | && (return_to <= handler->end_addr)) { |
216 | if (!trace) |
217 | printk("%s%s\n" , loglvl, handler->trap_name); |
218 | unwind_trap(task, pc, fp, trace, loglvl); |
219 | return; |
220 | } |
221 | } |
222 | pc -= ofs; |
223 | |
224 | if (trace) { |
225 | #ifdef CONFIG_STACKTRACE |
226 | if (trace->skip > 0) |
227 | trace->skip--; |
228 | else |
229 | trace->entries[trace->nr_entries++] = pc; |
230 | |
231 | if (trace->nr_entries >= trace->max_entries) |
232 | break; |
233 | #endif |
234 | } else { |
235 | /* Have we reached userland? */ |
236 | if (unlikely(pc == task_pt_regs(task)->pc)) { |
237 | printk("%s[<%p>] PID %lu [%s]\n" , |
238 | loglvl, (void *) pc, |
239 | (unsigned long) task->pid, |
240 | task->comm); |
241 | break; |
242 | } else |
243 | print_ip_sym(loglvl, ip: pc); |
244 | } |
245 | |
246 | /* Stop when we reach anything not part of the kernel */ |
247 | if (!kernel_text_address(addr: pc)) |
248 | break; |
249 | |
250 | if (lookup_prev_stack_frame(fp, pc, leaf_return, pprev_fp: &next_fp, |
251 | pprev_pc: &next_pc) == 0) { |
252 | ofs = sizeof(unsigned long); |
253 | pc = next_pc & ~3; |
254 | fp = next_fp; |
255 | leaf_return = 0; |
256 | } else { |
257 | pr_debug(" Failed to find previous stack frame\n" ); |
258 | break; |
259 | } |
260 | |
261 | pr_debug(" Next PC=%p, next FP=%p\n" , |
262 | (void *)next_pc, (void *)next_fp); |
263 | } |
264 | } |
265 | |
266 | /** |
267 | * microblaze_unwind - Stack unwinder for Microblaze (external entry point) |
268 | * @task : Task whose stack we are to unwind (NULL == current) |
269 | * @trace : Where to store stack backtrace (PC values). |
270 | * NULL == print backtrace to kernel log |
271 | * @loglvl : Used for printk log level if (trace == NULL). |
272 | */ |
273 | void microblaze_unwind(struct task_struct *task, struct stack_trace *trace, |
274 | const char *loglvl) |
275 | { |
276 | if (task) { |
277 | if (task == current) { |
278 | const struct pt_regs *regs = task_pt_regs(task); |
279 | microblaze_unwind_inner(task, pc: regs->pc, fp: regs->r1, |
280 | leaf_return: regs->r15, trace, loglvl); |
281 | } else { |
282 | struct thread_info *thread_info = |
283 | (struct thread_info *)(task->stack); |
284 | const struct cpu_context *cpu_context = |
285 | &thread_info->cpu_context; |
286 | |
287 | microblaze_unwind_inner(task, |
288 | pc: (unsigned long) &_switch_to, |
289 | fp: cpu_context->r1, |
290 | leaf_return: cpu_context->r15, |
291 | trace, loglvl); |
292 | } |
293 | } else { |
294 | unsigned long pc, fp; |
295 | |
296 | __asm__ __volatile__ ("or %0, r1, r0" : "=r" (fp)); |
297 | |
298 | __asm__ __volatile__ ( |
299 | "brlid %0, 0f;" |
300 | "nop;" |
301 | "0:" |
302 | : "=r" (pc) |
303 | ); |
304 | |
305 | /* Since we are not a leaf function, use leaf_return = 0 */ |
306 | microblaze_unwind_inner(current, pc, fp, leaf_return: 0, trace, loglvl); |
307 | } |
308 | } |
309 | |
310 | |