arch/tile: prevent corrupt top frame from causing backtracer runaway
The backtracer will normally cut itself off after 100 frames anyway,
but it's messy. With this change we notice that the frame being
reported is the same as the last one, and cut off the dump with a
message similar to what gdb displays in the same circumstance.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
diff --git a/arch/tile/kernel/stack.c b/arch/tile/kernel/stack.c
index ea2e0ce..0d54106b 100644
--- a/arch/tile/kernel/stack.c
+++ b/arch/tile/kernel/stack.c
@@ -30,6 +30,10 @@
#include <arch/abi.h>
#include <arch/interrupts.h>
+#define KBT_ONGOING 0 /* Backtrace still ongoing */
+#define KBT_DONE 1 /* Backtrace cleanly completed */
+#define KBT_RUNNING 2 /* Can't run backtrace on a running task */
+#define KBT_LOOP 3 /* Backtrace entered a loop */
/* Is address on the specified kernel stack? */
static int in_kernel_stack(struct KBacktraceIterator *kbt, VirtualAddress sp)
@@ -207,11 +211,11 @@
for (;;) {
do {
if (!KBacktraceIterator_is_sigreturn(kbt))
- return 1;
+ return KBT_ONGOING;
} while (backtrace_next(&kbt->it));
if (!KBacktraceIterator_restart(kbt))
- return 0;
+ return KBT_DONE;
}
}
@@ -264,7 +268,7 @@
kbt->pgtable = NULL;
kbt->verbose = 0; /* override in caller if desired */
kbt->profile = 0; /* override in caller if desired */
- kbt->end = 0;
+ kbt->end = KBT_ONGOING;
kbt->new_context = 0;
if (is_current) {
HV_PhysAddr pgdir_pa = hv_inquire_context().page_table;
@@ -290,7 +294,7 @@
if (regs == NULL) {
if (is_current || t->state == TASK_RUNNING) {
/* Can't do this; we need registers */
- kbt->end = 1;
+ kbt->end = KBT_RUNNING;
return;
}
pc = get_switch_to_pc();
@@ -305,26 +309,29 @@
}
backtrace_init(&kbt->it, read_memory_func, kbt, pc, lr, sp, r52);
- kbt->end = !KBacktraceIterator_next_item_inclusive(kbt);
+ kbt->end = KBacktraceIterator_next_item_inclusive(kbt);
}
EXPORT_SYMBOL(KBacktraceIterator_init);
int KBacktraceIterator_end(struct KBacktraceIterator *kbt)
{
- return kbt->end;
+ return kbt->end != KBT_ONGOING;
}
EXPORT_SYMBOL(KBacktraceIterator_end);
void KBacktraceIterator_next(struct KBacktraceIterator *kbt)
{
+ VirtualAddress old_pc = kbt->it.pc, old_sp = kbt->it.sp;
kbt->new_context = 0;
- if (!backtrace_next(&kbt->it) &&
- !KBacktraceIterator_restart(kbt)) {
- kbt->end = 1;
- return;
- }
-
- kbt->end = !KBacktraceIterator_next_item_inclusive(kbt);
+ if (!backtrace_next(&kbt->it) && !KBacktraceIterator_restart(kbt)) {
+ kbt->end = KBT_DONE;
+ return;
+ }
+ kbt->end = KBacktraceIterator_next_item_inclusive(kbt);
+ if (old_pc == kbt->it.pc && old_sp == kbt->it.sp) {
+ /* Trapped in a loop; give up. */
+ kbt->end = KBT_LOOP;
+ }
}
EXPORT_SYMBOL(KBacktraceIterator_next);
@@ -387,6 +394,8 @@
break;
}
}
+ if (kbt->end == KBT_LOOP)
+ pr_err("Stack dump stopped; next frame identical to this one\n");
if (headers)
pr_err("Stack dump complete\n");
}