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Subject[PATCH 1/3] x86/unwind: move common code into update_stack_state()
Date
The __unwind_start() and unwind_next_frame() functions have some
duplicated functionality. They both call decode_frame_pointer() and set
state->regs and state->bp accordingly. Move that functionality to a
common place in update_stack_state().

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
arch/x86/kernel/unwind_frame.c | 119 +++++++++++++++++++----------------------
1 file changed, 55 insertions(+), 64 deletions(-)

diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index 0833926..9098ef1 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -135,26 +135,59 @@ static struct pt_regs *decode_frame_pointer(unsigned long *bp)
return (struct pt_regs *)(regs & ~0x1);
}

-static bool update_stack_state(struct unwind_state *state, void *addr,
- size_t len)
+static bool update_stack_state(struct unwind_state *state,
+ unsigned long *next_bp)
{
struct stack_info *info = &state->stack_info;
- enum stack_type orig_type = info->type;
+ enum stack_type prev_type = info->type;
+ struct pt_regs *regs;
+ unsigned long *frame, *prev_frame_end;
+ 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);
+ } else {
+ frame = next_bp;
+ len = FRAME_HEADER_SIZE;
+ }

/*
- * If addr isn't on the current stack, switch to the next one.
+ * 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 'addr' could
- * be on a subsequent stack.
+ * that info->next_sp could point to an empty stack and the next bp
+ * could be on a subsequent stack.
*/
- while (!on_stack(info, addr, len))
+ while (!on_stack(info, frame, 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;
+ /* 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 original stack pointer for unwind_dump(): */
+ if (!state->orig_sp || info->type != prev_type)
+ state->orig_sp = frame;

return true;
}
@@ -162,14 +195,12 @@ static bool update_stack_state(struct unwind_state *state, void *addr,
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;
+ unsigned long *next_bp;

if (unwind_done(state))
return false;

- /* have we reached the end? */
+ /* Have we reached the end? */
if (state->regs && user_mode(state->regs))
goto the_end;

@@ -200,24 +231,14 @@ bool unwind_next_frame(struct unwind_state *state)
return true;
}

- /* get the next frame pointer */
+ /* 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);
+ next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task, *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)) {
+ /* Move to the next frame if it's safe: */
+ if (!update_stack_state(state, next_bp)) {
/*
* Don't warn on bad regs->bp. An interrupt in entry code
* might cause a false positive warning.
@@ -228,24 +249,6 @@ bool unwind_next_frame(struct unwind_state *state)
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:
@@ -263,13 +266,13 @@ bool unwind_next_frame(struct unwind_state *state)
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);
+ state->task->pid, next_bp);
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);
+ state->task->pid, next_bp);
unwind_dump(state, state->bp);
}
the_end:
@@ -281,35 +284,23 @@ 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;
+ unsigned long *bp;

memset(state, 0, sizeof(*state));
state->task = task;

- /* don't even attempt to start from user mode regs */
+ /* 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,
+ /* 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, frame, len);
+ update_stack_state(state, bp);

/*
* The caller can provide the address of the first frame directly
--
2.7.4
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