1 #include <linux/sched.h> 2 #include <asm/ptrace.h> 3 #include <asm/bitops.h> 4 #include <asm/stacktrace.h> 5 #include <asm/unwind.h> 6 7 #define FRAME_HEADER_SIZE (sizeof(long) * 2) 8 9 static void unwind_dump(struct unwind_state *state, unsigned long *sp) 10 { 11 static bool dumped_before = false; 12 bool prev_zero, zero = false; 13 unsigned long word; 14 15 if (dumped_before) 16 return; 17 18 dumped_before = true; 19 20 printk_deferred("unwind stack type:%d next_sp:%p mask:%lx graph_idx:%d\n", 21 state->stack_info.type, state->stack_info.next_sp, 22 state->stack_mask, state->graph_idx); 23 24 for (sp = state->orig_sp; sp < state->stack_info.end; sp++) { 25 word = READ_ONCE_NOCHECK(*sp); 26 27 prev_zero = zero; 28 zero = word == 0; 29 30 if (zero) { 31 if (!prev_zero) 32 printk_deferred("%p: %016x ...\n", sp, 0); 33 continue; 34 } 35 36 printk_deferred("%p: %016lx (%pB)\n", sp, word, (void *)word); 37 } 38 } 39 40 unsigned long unwind_get_return_address(struct unwind_state *state) 41 { 42 unsigned long addr; 43 unsigned long *addr_p = unwind_get_return_address_ptr(state); 44 45 if (unwind_done(state)) 46 return 0; 47 48 if (state->regs && user_mode(state->regs)) 49 return 0; 50 51 addr = ftrace_graph_ret_addr(state->task, &state->graph_idx, *addr_p, 52 addr_p); 53 54 return __kernel_text_address(addr) ? addr : 0; 55 } 56 EXPORT_SYMBOL_GPL(unwind_get_return_address); 57 58 static size_t regs_size(struct pt_regs *regs) 59 { 60 /* x86_32 regs from kernel mode are two words shorter: */ 61 if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs)) 62 return sizeof(*regs) - 2*sizeof(long); 63 64 return sizeof(*regs); 65 } 66 67 static bool is_last_task_frame(struct unwind_state *state) 68 { 69 unsigned long bp = (unsigned long)state->bp; 70 unsigned long regs = (unsigned long)task_pt_regs(state->task); 71 72 /* 73 * We have to check for the last task frame at two different locations 74 * because gcc can occasionally decide to realign the stack pointer and 75 * change the offset of the stack frame by a word in the prologue of a 76 * function called by head/entry code. 77 */ 78 return bp == regs - FRAME_HEADER_SIZE || 79 bp == regs - FRAME_HEADER_SIZE - sizeof(long); 80 } 81 82 /* 83 * This determines if the frame pointer actually contains an encoded pointer to 84 * pt_regs on the stack. See ENCODE_FRAME_POINTER. 85 */ 86 static struct pt_regs *decode_frame_pointer(unsigned long *bp) 87 { 88 unsigned long regs = (unsigned long)bp; 89 90 if (!(regs & 0x1)) 91 return NULL; 92 93 return (struct pt_regs *)(regs & ~0x1); 94 } 95 96 static bool update_stack_state(struct unwind_state *state, void *addr, 97 size_t len) 98 { 99 struct stack_info *info = &state->stack_info; 100 enum stack_type orig_type = info->type; 101 102 /* 103 * If addr isn't on the current stack, switch to the next one. 104 * 105 * We may have to traverse multiple stacks to deal with the possibility 106 * that 'info->next_sp' could point to an empty stack and 'addr' could 107 * be on a subsequent stack. 108 */ 109 while (!on_stack(info, addr, len)) 110 if (get_stack_info(info->next_sp, state->task, info, 111 &state->stack_mask)) 112 return false; 113 114 if (!state->orig_sp || info->type != orig_type) 115 state->orig_sp = addr; 116 117 return true; 118 } 119 120 bool unwind_next_frame(struct unwind_state *state) 121 { 122 struct pt_regs *regs; 123 unsigned long *next_bp, *next_frame; 124 size_t next_len; 125 enum stack_type prev_type = state->stack_info.type; 126 127 if (unwind_done(state)) 128 return false; 129 130 /* have we reached the end? */ 131 if (state->regs && user_mode(state->regs)) 132 goto the_end; 133 134 if (is_last_task_frame(state)) { 135 regs = task_pt_regs(state->task); 136 137 /* 138 * kthreads (other than the boot CPU's idle thread) have some 139 * partial regs at the end of their stack which were placed 140 * there by copy_thread_tls(). But the regs don't have any 141 * useful information, so we can skip them. 142 * 143 * This user_mode() check is slightly broader than a PF_KTHREAD 144 * check because it also catches the awkward situation where a 145 * newly forked kthread transitions into a user task by calling 146 * do_execve(), which eventually clears PF_KTHREAD. 147 */ 148 if (!user_mode(regs)) 149 goto the_end; 150 151 /* 152 * We're almost at the end, but not quite: there's still the 153 * syscall regs frame. Entry code doesn't encode the regs 154 * pointer for syscalls, so we have to set it manually. 155 */ 156 state->regs = regs; 157 state->bp = NULL; 158 return true; 159 } 160 161 /* get the next frame pointer */ 162 if (state->regs) 163 next_bp = (unsigned long *)state->regs->bp; 164 else 165 next_bp = (unsigned long *)*state->bp; 166 167 /* is the next frame pointer an encoded pointer to pt_regs? */ 168 regs = decode_frame_pointer(next_bp); 169 if (regs) { 170 next_frame = (unsigned long *)regs; 171 next_len = sizeof(*regs); 172 } else { 173 next_frame = next_bp; 174 next_len = FRAME_HEADER_SIZE; 175 } 176 177 /* make sure the next frame's data is accessible */ 178 if (!update_stack_state(state, next_frame, next_len)) { 179 /* 180 * Don't warn on bad regs->bp. An interrupt in entry code 181 * might cause a false positive warning. 182 */ 183 if (state->regs) 184 goto the_end; 185 186 goto bad_address; 187 } 188 189 /* Make sure it only unwinds up and doesn't overlap the last frame: */ 190 if (state->stack_info.type == prev_type) { 191 if (state->regs && (void *)next_frame < (void *)state->regs + regs_size(state->regs)) 192 goto bad_address; 193 194 if (state->bp && (void *)next_frame < (void *)state->bp + FRAME_HEADER_SIZE) 195 goto bad_address; 196 } 197 198 /* move to the next frame */ 199 if (regs) { 200 state->regs = regs; 201 state->bp = NULL; 202 } else { 203 state->bp = next_bp; 204 state->regs = NULL; 205 } 206 207 return true; 208 209 bad_address: 210 if (state->regs) { 211 printk_deferred_once(KERN_WARNING 212 "WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n", 213 state->regs, state->task->comm, 214 state->task->pid, next_frame); 215 unwind_dump(state, (unsigned long *)state->regs); 216 } else { 217 printk_deferred_once(KERN_WARNING 218 "WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n", 219 state->bp, state->task->comm, 220 state->task->pid, next_frame); 221 unwind_dump(state, state->bp); 222 } 223 the_end: 224 state->stack_info.type = STACK_TYPE_UNKNOWN; 225 return false; 226 } 227 EXPORT_SYMBOL_GPL(unwind_next_frame); 228 229 void __unwind_start(struct unwind_state *state, struct task_struct *task, 230 struct pt_regs *regs, unsigned long *first_frame) 231 { 232 unsigned long *bp, *frame; 233 size_t len; 234 235 memset(state, 0, sizeof(*state)); 236 state->task = task; 237 238 /* don't even attempt to start from user mode regs */ 239 if (regs && user_mode(regs)) { 240 state->stack_info.type = STACK_TYPE_UNKNOWN; 241 return; 242 } 243 244 /* set up the starting stack frame */ 245 bp = get_frame_pointer(task, regs); 246 regs = decode_frame_pointer(bp); 247 if (regs) { 248 state->regs = regs; 249 frame = (unsigned long *)regs; 250 len = sizeof(*regs); 251 } else { 252 state->bp = bp; 253 frame = bp; 254 len = FRAME_HEADER_SIZE; 255 } 256 257 /* initialize stack info and make sure the frame data is accessible */ 258 get_stack_info(frame, state->task, &state->stack_info, 259 &state->stack_mask); 260 update_stack_state(state, frame, len); 261 262 /* 263 * The caller can provide the address of the first frame directly 264 * (first_frame) or indirectly (regs->sp) to indicate which stack frame 265 * to start unwinding at. Skip ahead until we reach it. 266 */ 267 while (!unwind_done(state) && 268 (!on_stack(&state->stack_info, first_frame, sizeof(long)) || 269 state->bp < first_frame)) 270 unwind_next_frame(state); 271 } 272 EXPORT_SYMBOL_GPL(__unwind_start); 273