From dabe98c972091818762e02841ab1f982e573e7d0 Mon Sep 17 00:00:00 2001 From: Chris Metcalf Date: Thu, 14 Oct 2010 15:19:04 -0400 Subject: 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 --- arch/tile/kernel/stack.c | 35 ++++++++++++++++++++++------------- 1 file changed, 22 insertions(+), 13 deletions(-) (limited to 'arch/tile/kernel') diff --git a/arch/tile/kernel/stack.c b/arch/tile/kernel/stack.c index ea2e0ce28380..0d54106be3d6 100644 --- a/arch/tile/kernel/stack.c +++ b/arch/tile/kernel/stack.c @@ -30,6 +30,10 @@ #include #include +#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"); } -- cgit v1.2.2