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x86/unwind: Move common code into update_stack_state()
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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 <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: Dave Jones <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/a2ee4801113f6d2300d58f08f6b69f85edf4eb43.1492020577.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <[email protected]>
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@jpoimboe
jpoimboe authored and Ingo Molnar committed Apr 14, 2017
1 parent b5effd3 commit 5ed8d8b
Showing 1 changed file with 55 additions and 64 deletions.
119 changes: 55 additions & 64 deletions arch/x86/kernel/unwind_frame.c
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Original file line number Diff line number Diff line change
Expand Up @@ -135,41 +135,72 @@ 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;
}

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;

Expand Down Expand Up @@ -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.
Expand All @@ -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:
Expand All @@ -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:
Expand All @@ -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
Expand Down

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