| #include <linux/sched.h> |
| #include <asm/ptrace.h> |
| #include <asm/bitops.h> |
| #include <asm/stacktrace.h> |
| #include <asm/unwind.h> |
| |
| #define FRAME_HEADER_SIZE (sizeof(long) * 2) |
| |
| static void unwind_dump(struct unwind_state *state, unsigned long *sp) |
| { |
| static bool dumped_before = false; |
| bool prev_zero, zero = false; |
| unsigned long word; |
| |
| if (dumped_before) |
| return; |
| |
| dumped_before = true; |
| |
| printk_deferred("unwind stack type:%d next_sp:%p mask:%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 < state->stack_info.end; sp++) { |
| word = READ_ONCE_NOCHECK(*sp); |
| |
| prev_zero = zero; |
| zero = word == 0; |
| |
| if (zero) { |
| if (!prev_zero) |
| printk_deferred("%p: %016x ...\n", sp, 0); |
| continue; |
| } |
| |
| printk_deferred("%p: %016lx (%pB)\n", sp, word, (void *)word); |
| } |
| } |
| |
| unsigned long unwind_get_return_address(struct unwind_state *state) |
| { |
| unsigned long addr; |
| unsigned long *addr_p = unwind_get_return_address_ptr(state); |
| |
| if (unwind_done(state)) |
| return 0; |
| |
| if (state->regs && user_mode(state->regs)) |
| return 0; |
| |
| addr = ftrace_graph_ret_addr(state->task, &state->graph_idx, *addr_p, |
| addr_p); |
| |
| return __kernel_text_address(addr) ? addr : 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 is_last_task_frame(struct unwind_state *state) |
| { |
| unsigned long bp = (unsigned long)state->bp; |
| unsigned long regs = (unsigned long)task_pt_regs(state->task); |
| |
| /* |
| * We have to check for the last task frame at two different locations |
| * because gcc can occasionally decide to realign the stack pointer and |
| * change the offset of the stack frame by a word in the prologue of a |
| * function called by head/entry code. |
| */ |
| return bp == regs - FRAME_HEADER_SIZE || |
| bp == regs - FRAME_HEADER_SIZE - sizeof(long); |
| } |
| |
| /* |
| * 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, void *addr, |
| size_t len) |
| { |
| struct stack_info *info = &state->stack_info; |
| enum stack_type orig_type = info->type; |
| |
| /* |
| * If addr 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 'addr' could |
| * be on a subsequent stack. |
| */ |
| while (!on_stack(info, addr, len)) |
| if (get_stack_info(info->next_sp, state->task, info, |
| &state->stack_mask)) |
| return false; |
| |
| if (!state->orig_sp || info->type != orig_type) |
| state->orig_sp = addr; |
| |
| return true; |
| } |
| |
| bool unwind_next_frame(struct unwind_state *state) |
| { |
| struct pt_regs *regs; |
| unsigned long *next_bp, *next_frame; |
| size_t next_len; |
| enum stack_type prev_type = state->stack_info.type; |
| |
| 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; |
| return true; |
| } |
| |
| /* get the next frame pointer */ |
| if (state->regs) |
| next_bp = (unsigned long *)state->regs->bp; |
| else |
| next_bp = (unsigned long *)*state->bp; |
| |
| /* is the next frame pointer an encoded pointer to pt_regs? */ |
| regs = decode_frame_pointer(next_bp); |
| if (regs) { |
| next_frame = (unsigned long *)regs; |
| next_len = sizeof(*regs); |
| } else { |
| next_frame = next_bp; |
| next_len = FRAME_HEADER_SIZE; |
| } |
| |
| /* make sure the next frame's data is accessible */ |
| if (!update_stack_state(state, next_frame, next_len)) { |
| /* |
| * Don't warn on bad regs->bp. An interrupt in entry code |
| * might cause a false positive warning. |
| */ |
| if (state->regs) |
| goto the_end; |
| |
| goto bad_address; |
| } |
| |
| /* Make sure it only unwinds up and doesn't overlap the last frame: */ |
| if (state->stack_info.type == prev_type) { |
| if (state->regs && (void *)next_frame < (void *)state->regs + regs_size(state->regs)) |
| goto bad_address; |
| |
| if (state->bp && (void *)next_frame < (void *)state->bp + FRAME_HEADER_SIZE) |
| goto bad_address; |
| } |
| |
| /* move to the next frame */ |
| if (regs) { |
| state->regs = regs; |
| state->bp = NULL; |
| } else { |
| state->bp = next_bp; |
| state->regs = NULL; |
| } |
| |
| return true; |
| |
| bad_address: |
| 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_frame); |
| unwind_dump(state, (unsigned long *)state->regs); |
| } 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_frame); |
| unwind_dump(state, state->bp); |
| } |
| 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, *frame; |
| size_t len; |
| |
| memset(state, 0, sizeof(*state)); |
| state->task = task; |
| |
| /* don't even attempt to start from user mode regs */ |
| if (regs && user_mode(regs)) { |
| state->stack_info.type = STACK_TYPE_UNKNOWN; |
| return; |
| } |
| |
| /* set up the starting stack frame */ |
| bp = get_frame_pointer(task, regs); |
| regs = decode_frame_pointer(bp); |
| if (regs) { |
| state->regs = regs; |
| frame = (unsigned long *)regs; |
| len = sizeof(*regs); |
| } else { |
| state->bp = bp; |
| frame = bp; |
| len = FRAME_HEADER_SIZE; |
| } |
| |
| /* initialize stack info and make sure the frame data is accessible */ |
| get_stack_info(frame, state->task, &state->stack_info, |
| &state->stack_mask); |
| update_stack_state(state, frame, len); |
| |
| /* |
| * 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); |