17c7900f8SJosh Poimboeuf #include <linux/sched.h> 229930025SIngo Molnar #include <linux/sched/task.h> 368db0cf1SIngo Molnar #include <linux/sched/task_stack.h> 47c7900f8SJosh Poimboeuf #include <asm/ptrace.h> 57c7900f8SJosh Poimboeuf #include <asm/bitops.h> 67c7900f8SJosh Poimboeuf #include <asm/stacktrace.h> 77c7900f8SJosh Poimboeuf #include <asm/unwind.h> 87c7900f8SJosh Poimboeuf 97c7900f8SJosh Poimboeuf #define FRAME_HEADER_SIZE (sizeof(long) * 2) 107c7900f8SJosh Poimboeuf 1184936118SJosh Poimboeuf /* 1284936118SJosh Poimboeuf * This disables KASAN checking when reading a value from another task's stack, 1384936118SJosh Poimboeuf * since the other task could be running on another CPU and could have poisoned 1484936118SJosh Poimboeuf * the stack in the meantime. 1584936118SJosh Poimboeuf */ 1684936118SJosh Poimboeuf #define READ_ONCE_TASK_STACK(task, x) \ 1784936118SJosh Poimboeuf ({ \ 1884936118SJosh Poimboeuf unsigned long val; \ 1984936118SJosh Poimboeuf if (task == current) \ 2084936118SJosh Poimboeuf val = READ_ONCE(x); \ 2184936118SJosh Poimboeuf else \ 2284936118SJosh Poimboeuf val = READ_ONCE_NOCHECK(x); \ 2384936118SJosh Poimboeuf val; \ 2484936118SJosh Poimboeuf }) 2584936118SJosh Poimboeuf 268b5e99f0SJosh Poimboeuf static void unwind_dump(struct unwind_state *state, unsigned long *sp) 278b5e99f0SJosh Poimboeuf { 288b5e99f0SJosh Poimboeuf static bool dumped_before = false; 298b5e99f0SJosh Poimboeuf bool prev_zero, zero = false; 308b5e99f0SJosh Poimboeuf unsigned long word; 318b5e99f0SJosh Poimboeuf 328b5e99f0SJosh Poimboeuf if (dumped_before) 338b5e99f0SJosh Poimboeuf return; 348b5e99f0SJosh Poimboeuf 358b5e99f0SJosh Poimboeuf dumped_before = true; 368b5e99f0SJosh Poimboeuf 378b5e99f0SJosh Poimboeuf printk_deferred("unwind stack type:%d next_sp:%p mask:%lx graph_idx:%d\n", 388b5e99f0SJosh Poimboeuf state->stack_info.type, state->stack_info.next_sp, 398b5e99f0SJosh Poimboeuf state->stack_mask, state->graph_idx); 408b5e99f0SJosh Poimboeuf 418b5e99f0SJosh Poimboeuf for (sp = state->orig_sp; sp < state->stack_info.end; sp++) { 428b5e99f0SJosh Poimboeuf word = READ_ONCE_NOCHECK(*sp); 438b5e99f0SJosh Poimboeuf 448b5e99f0SJosh Poimboeuf prev_zero = zero; 458b5e99f0SJosh Poimboeuf zero = word == 0; 468b5e99f0SJosh Poimboeuf 478b5e99f0SJosh Poimboeuf if (zero) { 488b5e99f0SJosh Poimboeuf if (!prev_zero) 498b5e99f0SJosh Poimboeuf printk_deferred("%p: %016x ...\n", sp, 0); 508b5e99f0SJosh Poimboeuf continue; 518b5e99f0SJosh Poimboeuf } 528b5e99f0SJosh Poimboeuf 538b5e99f0SJosh Poimboeuf printk_deferred("%p: %016lx (%pB)\n", sp, word, (void *)word); 548b5e99f0SJosh Poimboeuf } 558b5e99f0SJosh Poimboeuf } 568b5e99f0SJosh Poimboeuf 577c7900f8SJosh Poimboeuf unsigned long unwind_get_return_address(struct unwind_state *state) 587c7900f8SJosh Poimboeuf { 597c7900f8SJosh Poimboeuf if (unwind_done(state)) 607c7900f8SJosh Poimboeuf return 0; 617c7900f8SJosh Poimboeuf 62*6bcdf9d5SJosh Poimboeuf return __kernel_text_address(state->ip) ? state->ip : 0; 637c7900f8SJosh Poimboeuf } 647c7900f8SJosh Poimboeuf EXPORT_SYMBOL_GPL(unwind_get_return_address); 657c7900f8SJosh Poimboeuf 6624d86f59SJosh Poimboeuf static size_t regs_size(struct pt_regs *regs) 6724d86f59SJosh Poimboeuf { 6824d86f59SJosh Poimboeuf /* x86_32 regs from kernel mode are two words shorter: */ 6924d86f59SJosh Poimboeuf if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs)) 7024d86f59SJosh Poimboeuf return sizeof(*regs) - 2*sizeof(long); 7124d86f59SJosh Poimboeuf 7224d86f59SJosh Poimboeuf return sizeof(*regs); 7324d86f59SJosh Poimboeuf } 7424d86f59SJosh Poimboeuf 7587a6b297SJosh Poimboeuf #ifdef CONFIG_X86_32 7687a6b297SJosh Poimboeuf #define GCC_REALIGN_WORDS 3 7787a6b297SJosh Poimboeuf #else 7887a6b297SJosh Poimboeuf #define GCC_REALIGN_WORDS 1 7987a6b297SJosh Poimboeuf #endif 8087a6b297SJosh Poimboeuf 81acb4608aSJosh Poimboeuf static bool is_last_task_frame(struct unwind_state *state) 82acb4608aSJosh Poimboeuf { 8387a6b297SJosh Poimboeuf unsigned long *last_bp = (unsigned long *)task_pt_regs(state->task) - 2; 8487a6b297SJosh Poimboeuf unsigned long *aligned_bp = last_bp - GCC_REALIGN_WORDS; 85acb4608aSJosh Poimboeuf 868023e0e2SJosh Poimboeuf /* 878023e0e2SJosh Poimboeuf * We have to check for the last task frame at two different locations 888023e0e2SJosh Poimboeuf * because gcc can occasionally decide to realign the stack pointer and 8987a6b297SJosh Poimboeuf * change the offset of the stack frame in the prologue of a function 9087a6b297SJosh Poimboeuf * called by head/entry code. Examples: 9187a6b297SJosh Poimboeuf * 9287a6b297SJosh Poimboeuf * <start_secondary>: 9387a6b297SJosh Poimboeuf * push %edi 9487a6b297SJosh Poimboeuf * lea 0x8(%esp),%edi 9587a6b297SJosh Poimboeuf * and $0xfffffff8,%esp 9687a6b297SJosh Poimboeuf * pushl -0x4(%edi) 9787a6b297SJosh Poimboeuf * push %ebp 9887a6b297SJosh Poimboeuf * mov %esp,%ebp 9987a6b297SJosh Poimboeuf * 10087a6b297SJosh Poimboeuf * <x86_64_start_kernel>: 10187a6b297SJosh Poimboeuf * lea 0x8(%rsp),%r10 10287a6b297SJosh Poimboeuf * and $0xfffffffffffffff0,%rsp 10387a6b297SJosh Poimboeuf * pushq -0x8(%r10) 10487a6b297SJosh Poimboeuf * push %rbp 10587a6b297SJosh Poimboeuf * mov %rsp,%rbp 10687a6b297SJosh Poimboeuf * 10787a6b297SJosh Poimboeuf * Note that after aligning the stack, it pushes a duplicate copy of 10887a6b297SJosh Poimboeuf * the return address before pushing the frame pointer. 1098023e0e2SJosh Poimboeuf */ 11087a6b297SJosh Poimboeuf return (state->bp == last_bp || 11187a6b297SJosh Poimboeuf (state->bp == aligned_bp && *(aligned_bp+1) == *(last_bp+1))); 112acb4608aSJosh Poimboeuf } 113acb4608aSJosh Poimboeuf 114946c1911SJosh Poimboeuf /* 115946c1911SJosh Poimboeuf * This determines if the frame pointer actually contains an encoded pointer to 116946c1911SJosh Poimboeuf * pt_regs on the stack. See ENCODE_FRAME_POINTER. 117946c1911SJosh Poimboeuf */ 118946c1911SJosh Poimboeuf static struct pt_regs *decode_frame_pointer(unsigned long *bp) 119946c1911SJosh Poimboeuf { 120946c1911SJosh Poimboeuf unsigned long regs = (unsigned long)bp; 121946c1911SJosh Poimboeuf 122946c1911SJosh Poimboeuf if (!(regs & 0x1)) 123946c1911SJosh Poimboeuf return NULL; 124946c1911SJosh Poimboeuf 125946c1911SJosh Poimboeuf return (struct pt_regs *)(regs & ~0x1); 126946c1911SJosh Poimboeuf } 127946c1911SJosh Poimboeuf 1285ed8d8bbSJosh Poimboeuf static bool update_stack_state(struct unwind_state *state, 1295ed8d8bbSJosh Poimboeuf unsigned long *next_bp) 1307c7900f8SJosh Poimboeuf { 1317c7900f8SJosh Poimboeuf struct stack_info *info = &state->stack_info; 1325ed8d8bbSJosh Poimboeuf enum stack_type prev_type = info->type; 1335ed8d8bbSJosh Poimboeuf struct pt_regs *regs; 134*6bcdf9d5SJosh Poimboeuf unsigned long *frame, *prev_frame_end, *addr_p, addr; 1355ed8d8bbSJosh Poimboeuf size_t len; 1365ed8d8bbSJosh Poimboeuf 1375ed8d8bbSJosh Poimboeuf if (state->regs) 1385ed8d8bbSJosh Poimboeuf prev_frame_end = (void *)state->regs + regs_size(state->regs); 1395ed8d8bbSJosh Poimboeuf else 1405ed8d8bbSJosh Poimboeuf prev_frame_end = (void *)state->bp + FRAME_HEADER_SIZE; 1415ed8d8bbSJosh Poimboeuf 1425ed8d8bbSJosh Poimboeuf /* Is the next frame pointer an encoded pointer to pt_regs? */ 1435ed8d8bbSJosh Poimboeuf regs = decode_frame_pointer(next_bp); 1445ed8d8bbSJosh Poimboeuf if (regs) { 1455ed8d8bbSJosh Poimboeuf frame = (unsigned long *)regs; 1465ed8d8bbSJosh Poimboeuf len = regs_size(regs); 1475ed8d8bbSJosh Poimboeuf } else { 1485ed8d8bbSJosh Poimboeuf frame = next_bp; 1495ed8d8bbSJosh Poimboeuf len = FRAME_HEADER_SIZE; 1505ed8d8bbSJosh Poimboeuf } 1517c7900f8SJosh Poimboeuf 1527c7900f8SJosh Poimboeuf /* 1535ed8d8bbSJosh Poimboeuf * If the next bp isn't on the current stack, switch to the next one. 1547c7900f8SJosh Poimboeuf * 1557c7900f8SJosh Poimboeuf * We may have to traverse multiple stacks to deal with the possibility 1565ed8d8bbSJosh Poimboeuf * that info->next_sp could point to an empty stack and the next bp 1575ed8d8bbSJosh Poimboeuf * could be on a subsequent stack. 1587c7900f8SJosh Poimboeuf */ 1595ed8d8bbSJosh Poimboeuf while (!on_stack(info, frame, len)) 1607c7900f8SJosh Poimboeuf if (get_stack_info(info->next_sp, state->task, info, 1617c7900f8SJosh Poimboeuf &state->stack_mask)) 1627c7900f8SJosh Poimboeuf return false; 1637c7900f8SJosh Poimboeuf 1645ed8d8bbSJosh Poimboeuf /* Make sure it only unwinds up and doesn't overlap the prev frame: */ 1655ed8d8bbSJosh Poimboeuf if (state->orig_sp && state->stack_info.type == prev_type && 1665ed8d8bbSJosh Poimboeuf frame < prev_frame_end) 1675ed8d8bbSJosh Poimboeuf return false; 1685ed8d8bbSJosh Poimboeuf 1695ed8d8bbSJosh Poimboeuf /* Move state to the next frame: */ 1705ed8d8bbSJosh Poimboeuf if (regs) { 1715ed8d8bbSJosh Poimboeuf state->regs = regs; 1725ed8d8bbSJosh Poimboeuf state->bp = NULL; 1735ed8d8bbSJosh Poimboeuf } else { 1745ed8d8bbSJosh Poimboeuf state->bp = next_bp; 1755ed8d8bbSJosh Poimboeuf state->regs = NULL; 1765ed8d8bbSJosh Poimboeuf } 1775ed8d8bbSJosh Poimboeuf 178*6bcdf9d5SJosh Poimboeuf /* Save the return address: */ 179*6bcdf9d5SJosh Poimboeuf if (state->regs && user_mode(state->regs)) 180*6bcdf9d5SJosh Poimboeuf state->ip = 0; 181*6bcdf9d5SJosh Poimboeuf else { 182*6bcdf9d5SJosh Poimboeuf addr_p = unwind_get_return_address_ptr(state); 183*6bcdf9d5SJosh Poimboeuf addr = READ_ONCE_TASK_STACK(state->task, *addr_p); 184*6bcdf9d5SJosh Poimboeuf state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, 185*6bcdf9d5SJosh Poimboeuf addr, addr_p); 186*6bcdf9d5SJosh Poimboeuf } 187*6bcdf9d5SJosh Poimboeuf 1885ed8d8bbSJosh Poimboeuf /* Save the original stack pointer for unwind_dump(): */ 1895ed8d8bbSJosh Poimboeuf if (!state->orig_sp || info->type != prev_type) 1905ed8d8bbSJosh Poimboeuf state->orig_sp = frame; 1918b5e99f0SJosh Poimboeuf 1927c7900f8SJosh Poimboeuf return true; 1937c7900f8SJosh Poimboeuf } 1947c7900f8SJosh Poimboeuf 1957c7900f8SJosh Poimboeuf bool unwind_next_frame(struct unwind_state *state) 1967c7900f8SJosh Poimboeuf { 197946c1911SJosh Poimboeuf struct pt_regs *regs; 1985ed8d8bbSJosh Poimboeuf unsigned long *next_bp; 1997c7900f8SJosh Poimboeuf 2007c7900f8SJosh Poimboeuf if (unwind_done(state)) 2017c7900f8SJosh Poimboeuf return false; 2027c7900f8SJosh Poimboeuf 2035ed8d8bbSJosh Poimboeuf /* Have we reached the end? */ 204946c1911SJosh Poimboeuf if (state->regs && user_mode(state->regs)) 205946c1911SJosh Poimboeuf goto the_end; 206946c1911SJosh Poimboeuf 207acb4608aSJosh Poimboeuf if (is_last_task_frame(state)) { 208acb4608aSJosh Poimboeuf regs = task_pt_regs(state->task); 209acb4608aSJosh Poimboeuf 210acb4608aSJosh Poimboeuf /* 211acb4608aSJosh Poimboeuf * kthreads (other than the boot CPU's idle thread) have some 212acb4608aSJosh Poimboeuf * partial regs at the end of their stack which were placed 213acb4608aSJosh Poimboeuf * there by copy_thread_tls(). But the regs don't have any 214acb4608aSJosh Poimboeuf * useful information, so we can skip them. 215acb4608aSJosh Poimboeuf * 216acb4608aSJosh Poimboeuf * This user_mode() check is slightly broader than a PF_KTHREAD 217acb4608aSJosh Poimboeuf * check because it also catches the awkward situation where a 218acb4608aSJosh Poimboeuf * newly forked kthread transitions into a user task by calling 219acb4608aSJosh Poimboeuf * do_execve(), which eventually clears PF_KTHREAD. 220acb4608aSJosh Poimboeuf */ 221acb4608aSJosh Poimboeuf if (!user_mode(regs)) 222acb4608aSJosh Poimboeuf goto the_end; 223acb4608aSJosh Poimboeuf 224acb4608aSJosh Poimboeuf /* 225acb4608aSJosh Poimboeuf * We're almost at the end, but not quite: there's still the 226acb4608aSJosh Poimboeuf * syscall regs frame. Entry code doesn't encode the regs 227acb4608aSJosh Poimboeuf * pointer for syscalls, so we have to set it manually. 228acb4608aSJosh Poimboeuf */ 229acb4608aSJosh Poimboeuf state->regs = regs; 230acb4608aSJosh Poimboeuf state->bp = NULL; 231*6bcdf9d5SJosh Poimboeuf state->ip = 0; 232acb4608aSJosh Poimboeuf return true; 233acb4608aSJosh Poimboeuf } 234acb4608aSJosh Poimboeuf 2355ed8d8bbSJosh Poimboeuf /* Get the next frame pointer: */ 236946c1911SJosh Poimboeuf if (state->regs) 237946c1911SJosh Poimboeuf next_bp = (unsigned long *)state->regs->bp; 238946c1911SJosh Poimboeuf else 23984936118SJosh Poimboeuf next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task, *state->bp); 2407c7900f8SJosh Poimboeuf 2415ed8d8bbSJosh Poimboeuf /* Move to the next frame if it's safe: */ 2425ed8d8bbSJosh Poimboeuf if (!update_stack_state(state, next_bp)) { 243c32c47c6SJosh Poimboeuf /* 244c32c47c6SJosh Poimboeuf * Don't warn on bad regs->bp. An interrupt in entry code 245c32c47c6SJosh Poimboeuf * might cause a false positive warning. 246c32c47c6SJosh Poimboeuf */ 247c32c47c6SJosh Poimboeuf if (state->regs) 248c32c47c6SJosh Poimboeuf goto the_end; 249c32c47c6SJosh Poimboeuf 250c32c47c6SJosh Poimboeuf goto bad_address; 251c32c47c6SJosh Poimboeuf } 252c32c47c6SJosh Poimboeuf 2537c7900f8SJosh Poimboeuf return true; 254946c1911SJosh Poimboeuf 255c32c47c6SJosh Poimboeuf bad_address: 256900742d8SJosh Poimboeuf /* 257900742d8SJosh Poimboeuf * When unwinding a non-current task, the task might actually be 258900742d8SJosh Poimboeuf * running on another CPU, in which case it could be modifying its 259900742d8SJosh Poimboeuf * stack while we're reading it. This is generally not a problem and 260900742d8SJosh Poimboeuf * can be ignored as long as the caller understands that unwinding 261900742d8SJosh Poimboeuf * another task will not always succeed. 262900742d8SJosh Poimboeuf */ 263900742d8SJosh Poimboeuf if (state->task != current) 264900742d8SJosh Poimboeuf goto the_end; 265900742d8SJosh Poimboeuf 26624d86f59SJosh Poimboeuf if (state->regs) { 26724d86f59SJosh Poimboeuf printk_deferred_once(KERN_WARNING 26824d86f59SJosh Poimboeuf "WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n", 26924d86f59SJosh Poimboeuf state->regs, state->task->comm, 2705ed8d8bbSJosh Poimboeuf state->task->pid, next_bp); 2718b5e99f0SJosh Poimboeuf unwind_dump(state, (unsigned long *)state->regs); 27224d86f59SJosh Poimboeuf } else { 273c32c47c6SJosh Poimboeuf printk_deferred_once(KERN_WARNING 274c32c47c6SJosh Poimboeuf "WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n", 275c32c47c6SJosh Poimboeuf state->bp, state->task->comm, 2765ed8d8bbSJosh Poimboeuf state->task->pid, next_bp); 2778b5e99f0SJosh Poimboeuf unwind_dump(state, state->bp); 27824d86f59SJosh Poimboeuf } 279946c1911SJosh Poimboeuf the_end: 280946c1911SJosh Poimboeuf state->stack_info.type = STACK_TYPE_UNKNOWN; 281946c1911SJosh Poimboeuf return false; 2827c7900f8SJosh Poimboeuf } 2837c7900f8SJosh Poimboeuf EXPORT_SYMBOL_GPL(unwind_next_frame); 2847c7900f8SJosh Poimboeuf 2857c7900f8SJosh Poimboeuf void __unwind_start(struct unwind_state *state, struct task_struct *task, 2867c7900f8SJosh Poimboeuf struct pt_regs *regs, unsigned long *first_frame) 2877c7900f8SJosh Poimboeuf { 2885ed8d8bbSJosh Poimboeuf unsigned long *bp; 289946c1911SJosh Poimboeuf 2907c7900f8SJosh Poimboeuf memset(state, 0, sizeof(*state)); 2917c7900f8SJosh Poimboeuf state->task = task; 2927c7900f8SJosh Poimboeuf 2935ed8d8bbSJosh Poimboeuf /* Don't even attempt to start from user mode regs: */ 2947c7900f8SJosh Poimboeuf if (regs && user_mode(regs)) { 2957c7900f8SJosh Poimboeuf state->stack_info.type = STACK_TYPE_UNKNOWN; 2967c7900f8SJosh Poimboeuf return; 2977c7900f8SJosh Poimboeuf } 2987c7900f8SJosh Poimboeuf 299946c1911SJosh Poimboeuf bp = get_frame_pointer(task, regs); 3007c7900f8SJosh Poimboeuf 3015ed8d8bbSJosh Poimboeuf /* Initialize stack info and make sure the frame data is accessible: */ 3025ed8d8bbSJosh Poimboeuf get_stack_info(bp, state->task, &state->stack_info, 3037c7900f8SJosh Poimboeuf &state->stack_mask); 3045ed8d8bbSJosh Poimboeuf update_stack_state(state, bp); 3057c7900f8SJosh Poimboeuf 3067c7900f8SJosh Poimboeuf /* 3077c7900f8SJosh Poimboeuf * The caller can provide the address of the first frame directly 3087c7900f8SJosh Poimboeuf * (first_frame) or indirectly (regs->sp) to indicate which stack frame 3097c7900f8SJosh Poimboeuf * to start unwinding at. Skip ahead until we reach it. 3107c7900f8SJosh Poimboeuf */ 3117c7900f8SJosh Poimboeuf while (!unwind_done(state) && 3127c7900f8SJosh Poimboeuf (!on_stack(&state->stack_info, first_frame, sizeof(long)) || 3137c7900f8SJosh Poimboeuf state->bp < first_frame)) 3147c7900f8SJosh Poimboeuf unwind_next_frame(state); 3157c7900f8SJosh Poimboeuf } 3167c7900f8SJosh Poimboeuf EXPORT_SYMBOL_GPL(__unwind_start); 317