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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 | #include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/interrupt.h>
#include <asm/sections.h>
#include <asm/ptrace.h>
#include <asm/bitops.h>
#include <asm/stacktrace.h>
#include <asm/unwind.h>
#define FRAME_HEADER_SIZE (sizeof(long) * 2)
/*
* This disables KASAN checking when reading a value from another task's stack,
* since the other task could be running on another CPU and could have poisoned
* the stack in the meantime.
*/
#define READ_ONCE_TASK_STACK(task, x) \
({ \
unsigned long val; \
if (task == current) \
val = READ_ONCE(x); \
else \
val = READ_ONCE_NOCHECK(x); \
val; \
})
static void unwind_dump(struct unwind_state *state)
{
static bool dumped_before = false;
bool prev_zero, zero = false;
unsigned long word, *sp;
struct stack_info stack_info = {0};
unsigned long visit_mask = 0;
if (dumped_before)
return;
dumped_before = true;
printk_deferred("unwind stack type:%d next_sp:%p mask:0x%lx graph_idx:%d\n",
state->stack_info.type, state->stack_info.next_sp,
state->stack_mask, state->graph_idx);
for (sp = state->orig_sp; sp; sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
break;
for (; sp < stack_info.end; sp++) {
word = READ_ONCE_NOCHECK(*sp);
prev_zero = zero;
zero = word == 0;
if (zero) {
if (!prev_zero)
printk_deferred("%p: %0*x ...\n",
sp, BITS_PER_LONG/4, 0);
continue;
}
printk_deferred("%p: %0*lx (%pB)\n",
sp, BITS_PER_LONG/4, word, (void *)word);
}
}
}
unsigned long unwind_get_return_address(struct unwind_state *state)
{
if (unwind_done(state))
return 0;
return __kernel_text_address(state->ip) ? state->ip : 0;
}
EXPORT_SYMBOL_GPL(unwind_get_return_address);
static size_t regs_size(struct pt_regs *regs)
{
/* x86_32 regs from kernel mode are two words shorter: */
if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs))
return sizeof(*regs) - 2*sizeof(long);
return sizeof(*regs);
}
static bool in_entry_code(unsigned long ip)
{
char *addr = (char *)ip;
if (addr >= __entry_text_start && addr < __entry_text_end)
return true;
#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
if (addr >= __irqentry_text_start && addr < __irqentry_text_end)
return true;
#endif
return false;
}
static inline unsigned long *last_frame(struct unwind_state *state)
{
return (unsigned long *)task_pt_regs(state->task) - 2;
}
static bool is_last_frame(struct unwind_state *state)
{
return state->bp == last_frame(state);
}
#ifdef CONFIG_X86_32
#define GCC_REALIGN_WORDS 3
#else
#define GCC_REALIGN_WORDS 1
#endif
static inline unsigned long *last_aligned_frame(struct unwind_state *state)
{
return last_frame(state) - GCC_REALIGN_WORDS;
}
static bool is_last_aligned_frame(struct unwind_state *state)
{
unsigned long *last_bp = last_frame(state);
unsigned long *aligned_bp = last_aligned_frame(state);
/*
* GCC can occasionally decide to realign the stack pointer and change
* the offset of the stack frame in the prologue of a function called
* by head/entry code. Examples:
*
* <start_secondary>:
* push %edi
* lea 0x8(%esp),%edi
* and $0xfffffff8,%esp
* pushl -0x4(%edi)
* push %ebp
* mov %esp,%ebp
*
* <x86_64_start_kernel>:
* lea 0x8(%rsp),%r10
* and $0xfffffffffffffff0,%rsp
* pushq -0x8(%r10)
* push %rbp
* mov %rsp,%rbp
*
* After aligning the stack, it pushes a duplicate copy of the return
* address before pushing the frame pointer.
*/
return (state->bp == aligned_bp && *(aligned_bp + 1) == *(last_bp + 1));
}
static bool is_last_ftrace_frame(struct unwind_state *state)
{
unsigned long *last_bp = last_frame(state);
unsigned long *last_ftrace_bp = last_bp - 3;
/*
* When unwinding from an ftrace handler of a function called by entry
* code, the stack layout of the last frame is:
*
* bp
* parent ret addr
* bp
* function ret addr
* parent ret addr
* pt_regs
* -----------------
*/
return (state->bp == last_ftrace_bp &&
*state->bp == *(state->bp + 2) &&
*(state->bp + 1) == *(state->bp + 4));
}
static bool is_last_task_frame(struct unwind_state *state)
{
return is_last_frame(state) || is_last_aligned_frame(state) ||
is_last_ftrace_frame(state);
}
/*
* This determines if the frame pointer actually contains an encoded pointer to
* pt_regs on the stack. See ENCODE_FRAME_POINTER.
*/
static struct pt_regs *decode_frame_pointer(unsigned long *bp)
{
unsigned long regs = (unsigned long)bp;
if (!(regs & 0x1))
return NULL;
return (struct pt_regs *)(regs & ~0x1);
}
static bool update_stack_state(struct unwind_state *state,
unsigned long *next_bp)
{
struct stack_info *info = &state->stack_info;
enum stack_type prev_type = info->type;
struct pt_regs *regs;
unsigned long *frame, *prev_frame_end, *addr_p, addr;
size_t len;
if (state->regs)
prev_frame_end = (void *)state->regs + regs_size(state->regs);
else
prev_frame_end = (void *)state->bp + FRAME_HEADER_SIZE;
/* Is the next frame pointer an encoded pointer to pt_regs? */
regs = decode_frame_pointer(next_bp);
if (regs) {
frame = (unsigned long *)regs;
len = regs_size(regs);
state->got_irq = true;
} else {
frame = next_bp;
len = FRAME_HEADER_SIZE;
}
/*
* If the next bp isn't on the current stack, switch to the next one.
*
* We may have to traverse multiple stacks to deal with the possibility
* that info->next_sp could point to an empty stack and the next bp
* could be on a subsequent stack.
*/
while (!on_stack(info, frame, len))
if (get_stack_info(info->next_sp, state->task, info,
&state->stack_mask))
return false;
/* Make sure it only unwinds up and doesn't overlap the prev frame: */
if (state->orig_sp && state->stack_info.type == prev_type &&
frame < prev_frame_end)
return false;
/* Move state to the next frame: */
if (regs) {
state->regs = regs;
state->bp = NULL;
} else {
state->bp = next_bp;
state->regs = NULL;
}
/* Save the return address: */
if (state->regs && user_mode(state->regs))
state->ip = 0;
else {
addr_p = unwind_get_return_address_ptr(state);
addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
addr, addr_p);
}
/* Save the original stack pointer for unwind_dump(): */
if (!state->orig_sp)
state->orig_sp = frame;
return true;
}
bool unwind_next_frame(struct unwind_state *state)
{
struct pt_regs *regs;
unsigned long *next_bp;
if (unwind_done(state))
return false;
/* Have we reached the end? */
if (state->regs && user_mode(state->regs))
goto the_end;
if (is_last_task_frame(state)) {
regs = task_pt_regs(state->task);
/*
* kthreads (other than the boot CPU's idle thread) have some
* partial regs at the end of their stack which were placed
* there by copy_thread_tls(). But the regs don't have any
* useful information, so we can skip them.
*
* This user_mode() check is slightly broader than a PF_KTHREAD
* check because it also catches the awkward situation where a
* newly forked kthread transitions into a user task by calling
* do_execve(), which eventually clears PF_KTHREAD.
*/
if (!user_mode(regs))
goto the_end;
/*
* We're almost at the end, but not quite: there's still the
* syscall regs frame. Entry code doesn't encode the regs
* pointer for syscalls, so we have to set it manually.
*/
state->regs = regs;
state->bp = NULL;
state->ip = 0;
return true;
}
/* Get the next frame pointer: */
if (state->regs)
next_bp = (unsigned long *)state->regs->bp;
else
next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task, *state->bp);
/* Move to the next frame if it's safe: */
if (!update_stack_state(state, next_bp))
goto bad_address;
return true;
bad_address:
state->error = true;
/*
* When unwinding a non-current task, the task might actually be
* running on another CPU, in which case it could be modifying its
* stack while we're reading it. This is generally not a problem and
* can be ignored as long as the caller understands that unwinding
* another task will not always succeed.
*/
if (state->task != current)
goto the_end;
/*
* Don't warn if the unwinder got lost due to an interrupt in entry
* code or in the C handler before the first frame pointer got set up:
*/
if (state->got_irq && in_entry_code(state->ip))
goto the_end;
if (state->regs &&
state->regs->sp >= (unsigned long)last_aligned_frame(state) &&
state->regs->sp < (unsigned long)task_pt_regs(state->task))
goto the_end;
if (state->regs) {
printk_deferred_once(KERN_WARNING
"WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",
state->regs, state->task->comm,
state->task->pid, next_bp);
unwind_dump(state);
} else {
printk_deferred_once(KERN_WARNING
"WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n",
state->bp, state->task->comm,
state->task->pid, next_bp);
unwind_dump(state);
}
the_end:
state->stack_info.type = STACK_TYPE_UNKNOWN;
return false;
}
EXPORT_SYMBOL_GPL(unwind_next_frame);
void __unwind_start(struct unwind_state *state, struct task_struct *task,
struct pt_regs *regs, unsigned long *first_frame)
{
unsigned long *bp;
memset(state, 0, sizeof(*state));
state->task = task;
state->got_irq = (regs);
/* Don't even attempt to start from user mode regs: */
if (regs && user_mode(regs)) {
state->stack_info.type = STACK_TYPE_UNKNOWN;
return;
}
bp = get_frame_pointer(task, regs);
/* Initialize stack info and make sure the frame data is accessible: */
get_stack_info(bp, state->task, &state->stack_info,
&state->stack_mask);
update_stack_state(state, bp);
/*
* The caller can provide the address of the first frame directly
* (first_frame) or indirectly (regs->sp) to indicate which stack frame
* to start unwinding at. Skip ahead until we reach it.
*/
while (!unwind_done(state) &&
(!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
state->bp < first_frame))
unwind_next_frame(state);
}
EXPORT_SYMBOL_GPL(__unwind_start);
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