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authorVasily Gorbik2019-11-27 17:37:51 +0100
committerVasily Gorbik2019-11-30 10:52:48 +0100
commit222ee9087a730b1df08d09baed0d03626e67600f (patch)
treed54f365c33449a1697ab1d0b4b07a7921ce6a837 /arch/s390
parentde6921ccbd0fb2882a1f615a6d3cdfbdcd64532c (diff)
s390/unwind: start unwinding from reliable state
A comment in arch/s390/include/asm/unwind.h says: > If 'first_frame' is not zero unwind_start skips unwind frames until it > reaches the specified stack pointer. > The end of the unwinding is indicated with unwind_done, this can be true > right after unwind_start, e.g. with first_frame!=0 that can not be found. > unwind_next_frame skips to the next frame. > Once the unwind is completed unwind_error() can be used to check if there > has been a situation where the unwinder could not correctly understand > the tasks call chain. With this change backchain unwinder now comply with behaviour described. As well as matches orc unwinder implementation. Now unwinder starts from reliable state, i.e. __unwind_start own stack frame is taken or stack frame generated by __switch_to (ksp) - both known to be valid. In case of pt_regs %r15 is better match for pt_regs psw, than sometimes random "sp" caller passed. Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/include/asm/unwind.h6
-rw-r--r--arch/s390/kernel/unwind_bc.c42
2 files changed, 31 insertions, 17 deletions
diff --git a/arch/s390/include/asm/unwind.h b/arch/s390/include/asm/unwind.h
index 5d6c8fe7a271..de9006b0cfeb 100644
--- a/arch/s390/include/asm/unwind.h
+++ b/arch/s390/include/asm/unwind.h
@@ -58,11 +58,11 @@ static inline bool unwind_error(struct unwind_state *state)
static inline void unwind_start(struct unwind_state *state,
struct task_struct *task,
struct pt_regs *regs,
- unsigned long sp)
+ unsigned long first_frame)
{
task = task ?: current;
- sp = sp ?: get_stack_pointer(task, regs);
- __unwind_start(state, task, regs, sp);
+ first_frame = first_frame ?: get_stack_pointer(task, regs);
+ __unwind_start(state, task, regs, first_frame);
}
static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
diff --git a/arch/s390/kernel/unwind_bc.c b/arch/s390/kernel/unwind_bc.c
index c5ebb8a4cdd6..e1371cdf9fa5 100644
--- a/arch/s390/kernel/unwind_bc.c
+++ b/arch/s390/kernel/unwind_bc.c
@@ -105,13 +105,11 @@ out_stop:
EXPORT_SYMBOL_GPL(unwind_next_frame);
void __unwind_start(struct unwind_state *state, struct task_struct *task,
- struct pt_regs *regs, unsigned long sp)
+ struct pt_regs *regs, unsigned long first_frame)
{
struct stack_info *info = &state->stack_info;
- unsigned long *mask = &state->stack_mask;
- bool reliable;
struct stack_frame *sf;
- unsigned long ip;
+ unsigned long ip, sp;
memset(state, 0, sizeof(*state));
state->task = task;
@@ -123,23 +121,28 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
return;
}
+ /* Get the instruction pointer from pt_regs or the stack frame */
+ if (regs) {
+ ip = regs->psw.addr;
+ sp = regs->gprs[15];
+ } else if (task == current) {
+ sp = current_frame_address();
+ } else {
+ sp = task->thread.ksp;
+ }
+
/* Get current stack pointer and initialize stack info */
- if (get_stack_info(sp, task, info, mask) != 0 ||
- !on_stack(info, sp, sizeof(struct stack_frame))) {
+ if (!update_stack_info(state, sp)) {
/* Something is wrong with the stack pointer */
info->type = STACK_TYPE_UNKNOWN;
state->error = true;
return;
}
- /* Get the instruction pointer from pt_regs or the stack frame */
- if (regs) {
- ip = READ_ONCE_NOCHECK(regs->psw.addr);
- reliable = true;
- } else {
- sf = (struct stack_frame *) sp;
+ if (!regs) {
+ /* Stack frame is within valid stack */
+ sf = (struct stack_frame *)sp;
ip = READ_ONCE_NOCHECK(sf->gprs[8]);
- reliable = false;
}
ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, NULL);
@@ -147,6 +150,17 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
/* Update unwind state */
state->sp = sp;
state->ip = ip;
- state->reliable = reliable;
+ state->reliable = true;
+
+ if (!first_frame)
+ return;
+ /* Skip through the call chain to the specified starting frame */
+ while (!unwind_done(state)) {
+ if (on_stack(&state->stack_info, first_frame, sizeof(struct stack_frame))) {
+ if (state->sp >= first_frame)
+ break;
+ }
+ unwind_next_frame(state);
+ }
}
EXPORT_SYMBOL_GPL(__unwind_start);