Steven J. Magnani | ce3266c | 2010-04-27 12:37:54 -0500 | [diff] [blame] | 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 | */ |
Michal Simek | 419ef34 | 2011-02-07 11:51:07 +0100 | [diff] [blame] | 186 | static void microblaze_unwind_inner(struct task_struct *task, |
Steven J. Magnani | ce3266c | 2010-04-27 12:37:54 -0500 | [diff] [blame] | 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 | |