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authorChris Metcalf <cmetcalf@tilera.com>2010-10-14 15:19:04 -0400
committerChris Metcalf <cmetcalf@tilera.com>2010-10-14 15:19:04 -0400
commitdabe98c972091818762e02841ab1f982e573e7d0 (patch)
tree3770c66ab60cc34225158e87a6532afa5704806c
parent45123f7e74e004848da765f3182cd401a38d354d (diff)
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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>
-rw-r--r--arch/tile/kernel/stack.c35
1 files changed, 22 insertions, 13 deletions
diff --git a/arch/tile/kernel/stack.c b/arch/tile/kernel/stack.c
index ea2e0ce2838..0d54106be3d 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 @@ static int KBacktraceIterator_next_item_inclusive(
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 @@ void KBacktraceIterator_init(struct KBacktraceIterator *kbt,
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 @@ void KBacktraceIterator_init(struct KBacktraceIterator *kbt,
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 @@ void KBacktraceIterator_init(struct KBacktraceIterator *kbt,
}
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 @@ void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
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");
}