mirror of https://gitee.com/openkylin/linux.git
301 lines
8.0 KiB
C
301 lines
8.0 KiB
C
#include <linux/sched.h>
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#include <linux/sched/task.h>
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#include <linux/sched/task_stack.h>
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#include <asm/ptrace.h>
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#include <asm/bitops.h>
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#include <asm/stacktrace.h>
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#include <asm/unwind.h>
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#define FRAME_HEADER_SIZE (sizeof(long) * 2)
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/*
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* This disables KASAN checking when reading a value from another task's stack,
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* since the other task could be running on another CPU and could have poisoned
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* the stack in the meantime.
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*/
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#define READ_ONCE_TASK_STACK(task, x) \
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({ \
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unsigned long val; \
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if (task == current) \
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val = READ_ONCE(x); \
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else \
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val = READ_ONCE_NOCHECK(x); \
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val; \
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})
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static void unwind_dump(struct unwind_state *state, unsigned long *sp)
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{
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static bool dumped_before = false;
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bool prev_zero, zero = false;
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unsigned long word;
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if (dumped_before)
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return;
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dumped_before = true;
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printk_deferred("unwind stack type:%d next_sp:%p mask:%lx graph_idx:%d\n",
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state->stack_info.type, state->stack_info.next_sp,
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state->stack_mask, state->graph_idx);
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for (sp = state->orig_sp; sp < state->stack_info.end; sp++) {
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word = READ_ONCE_NOCHECK(*sp);
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prev_zero = zero;
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zero = word == 0;
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if (zero) {
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if (!prev_zero)
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printk_deferred("%p: %016x ...\n", sp, 0);
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continue;
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}
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printk_deferred("%p: %016lx (%pB)\n", sp, word, (void *)word);
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}
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}
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unsigned long unwind_get_return_address(struct unwind_state *state)
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{
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unsigned long addr;
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unsigned long *addr_p = unwind_get_return_address_ptr(state);
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if (unwind_done(state))
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return 0;
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if (state->regs && user_mode(state->regs))
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return 0;
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addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
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addr = ftrace_graph_ret_addr(state->task, &state->graph_idx, addr,
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addr_p);
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return __kernel_text_address(addr) ? addr : 0;
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}
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EXPORT_SYMBOL_GPL(unwind_get_return_address);
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static size_t regs_size(struct pt_regs *regs)
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{
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/* x86_32 regs from kernel mode are two words shorter: */
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if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs))
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return sizeof(*regs) - 2*sizeof(long);
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return sizeof(*regs);
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}
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static bool is_last_task_frame(struct unwind_state *state)
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{
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unsigned long bp = (unsigned long)state->bp;
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unsigned long regs = (unsigned long)task_pt_regs(state->task);
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/*
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* We have to check for the last task frame at two different locations
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* because gcc can occasionally decide to realign the stack pointer and
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* change the offset of the stack frame by a word in the prologue of a
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* function called by head/entry code.
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*/
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return bp == regs - FRAME_HEADER_SIZE ||
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bp == regs - FRAME_HEADER_SIZE - sizeof(long);
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}
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/*
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* This determines if the frame pointer actually contains an encoded pointer to
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* pt_regs on the stack. See ENCODE_FRAME_POINTER.
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*/
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static struct pt_regs *decode_frame_pointer(unsigned long *bp)
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{
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unsigned long regs = (unsigned long)bp;
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if (!(regs & 0x1))
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return NULL;
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return (struct pt_regs *)(regs & ~0x1);
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}
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static bool update_stack_state(struct unwind_state *state, void *addr,
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size_t len)
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{
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struct stack_info *info = &state->stack_info;
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enum stack_type orig_type = info->type;
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/*
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* If addr isn't on the current stack, switch to the next one.
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*
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* We may have to traverse multiple stacks to deal with the possibility
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* that 'info->next_sp' could point to an empty stack and 'addr' could
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* be on a subsequent stack.
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*/
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while (!on_stack(info, addr, len))
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if (get_stack_info(info->next_sp, state->task, info,
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&state->stack_mask))
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return false;
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if (!state->orig_sp || info->type != orig_type)
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state->orig_sp = addr;
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return true;
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}
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bool unwind_next_frame(struct unwind_state *state)
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{
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struct pt_regs *regs;
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unsigned long *next_bp, *next_frame;
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size_t next_len;
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enum stack_type prev_type = state->stack_info.type;
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if (unwind_done(state))
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return false;
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/* have we reached the end? */
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if (state->regs && user_mode(state->regs))
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goto the_end;
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if (is_last_task_frame(state)) {
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regs = task_pt_regs(state->task);
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/*
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* kthreads (other than the boot CPU's idle thread) have some
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* partial regs at the end of their stack which were placed
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* there by copy_thread_tls(). But the regs don't have any
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* useful information, so we can skip them.
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*
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* This user_mode() check is slightly broader than a PF_KTHREAD
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* check because it also catches the awkward situation where a
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* newly forked kthread transitions into a user task by calling
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* do_execve(), which eventually clears PF_KTHREAD.
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*/
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if (!user_mode(regs))
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goto the_end;
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/*
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* We're almost at the end, but not quite: there's still the
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* syscall regs frame. Entry code doesn't encode the regs
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* pointer for syscalls, so we have to set it manually.
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*/
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state->regs = regs;
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state->bp = NULL;
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return true;
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}
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/* get the next frame pointer */
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if (state->regs)
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next_bp = (unsigned long *)state->regs->bp;
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else
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next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task,*state->bp);
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/* is the next frame pointer an encoded pointer to pt_regs? */
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regs = decode_frame_pointer(next_bp);
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if (regs) {
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next_frame = (unsigned long *)regs;
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next_len = sizeof(*regs);
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} else {
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next_frame = next_bp;
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next_len = FRAME_HEADER_SIZE;
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}
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/* make sure the next frame's data is accessible */
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if (!update_stack_state(state, next_frame, next_len)) {
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/*
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* Don't warn on bad regs->bp. An interrupt in entry code
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* might cause a false positive warning.
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*/
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if (state->regs)
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goto the_end;
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goto bad_address;
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}
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/* Make sure it only unwinds up and doesn't overlap the last frame: */
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if (state->stack_info.type == prev_type) {
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if (state->regs && (void *)next_frame < (void *)state->regs + regs_size(state->regs))
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goto bad_address;
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if (state->bp && (void *)next_frame < (void *)state->bp + FRAME_HEADER_SIZE)
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goto bad_address;
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}
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/* move to the next frame */
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if (regs) {
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state->regs = regs;
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state->bp = NULL;
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} else {
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state->bp = next_bp;
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state->regs = NULL;
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}
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return true;
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bad_address:
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/*
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* When unwinding a non-current task, the task might actually be
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* running on another CPU, in which case it could be modifying its
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* stack while we're reading it. This is generally not a problem and
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* can be ignored as long as the caller understands that unwinding
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* another task will not always succeed.
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*/
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if (state->task != current)
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goto the_end;
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if (state->regs) {
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printk_deferred_once(KERN_WARNING
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"WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",
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state->regs, state->task->comm,
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state->task->pid, next_frame);
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unwind_dump(state, (unsigned long *)state->regs);
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} else {
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printk_deferred_once(KERN_WARNING
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"WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n",
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state->bp, state->task->comm,
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state->task->pid, next_frame);
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unwind_dump(state, state->bp);
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}
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the_end:
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state->stack_info.type = STACK_TYPE_UNKNOWN;
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return false;
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}
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EXPORT_SYMBOL_GPL(unwind_next_frame);
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void __unwind_start(struct unwind_state *state, struct task_struct *task,
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struct pt_regs *regs, unsigned long *first_frame)
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{
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unsigned long *bp, *frame;
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size_t len;
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memset(state, 0, sizeof(*state));
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state->task = task;
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/* don't even attempt to start from user mode regs */
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if (regs && user_mode(regs)) {
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state->stack_info.type = STACK_TYPE_UNKNOWN;
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return;
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}
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/* set up the starting stack frame */
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bp = get_frame_pointer(task, regs);
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regs = decode_frame_pointer(bp);
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if (regs) {
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state->regs = regs;
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frame = (unsigned long *)regs;
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len = sizeof(*regs);
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} else {
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state->bp = bp;
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frame = bp;
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len = FRAME_HEADER_SIZE;
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}
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/* initialize stack info and make sure the frame data is accessible */
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get_stack_info(frame, state->task, &state->stack_info,
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&state->stack_mask);
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update_stack_state(state, frame, len);
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/*
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* The caller can provide the address of the first frame directly
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* (first_frame) or indirectly (regs->sp) to indicate which stack frame
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* to start unwinding at. Skip ahead until we reach it.
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*/
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while (!unwind_done(state) &&
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(!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
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state->bp < first_frame))
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unwind_next_frame(state);
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}
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EXPORT_SYMBOL_GPL(__unwind_start);
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