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@@ -103,8 +103,7 @@ static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
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if (kbt->verbose)
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pr_err(" <%s while in kernel mode>\n", fault);
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} else if (EX1_PL(p->ex1) == USER_PL &&
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- p->pc < PAGE_OFFSET &&
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- p->sp < PAGE_OFFSET) {
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+ p->sp < PAGE_OFFSET && p->sp != 0) {
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if (kbt->verbose)
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pr_err(" <%s while in user mode>\n", fault);
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} else if (kbt->verbose) {
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@@ -351,6 +350,26 @@ static void describe_addr(struct KBacktraceIterator *kbt,
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vma->vm_start, vma->vm_end - vma->vm_start);
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}
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+/*
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+ * Avoid possible crash recursion during backtrace. If it happens, it
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+ * makes it easy to lose the actual root cause of the failure, so we
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+ * put a simple guard on all the backtrace loops.
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+ */
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+static bool start_backtrace(void)
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+{
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+ if (current->thread.in_backtrace) {
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+ pr_err("Backtrace requested while in backtrace!\n");
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+ return false;
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+ }
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+ current->thread.in_backtrace = true;
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+ return true;
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+}
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+
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+static void end_backtrace(void)
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+{
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+ current->thread.in_backtrace = false;
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+}
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+
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/*
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* This method wraps the backtracer's more generic support.
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* It is only invoked from the architecture-specific code; show_stack()
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@@ -361,6 +380,8 @@ void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
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int i;
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int have_mmap_sem = 0;
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+ if (!start_backtrace())
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+ return;
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if (headers) {
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/*
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* Add a blank line since if we are called from panic(),
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@@ -402,6 +423,7 @@ void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
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pr_err("Stack dump complete\n");
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if (have_mmap_sem)
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up_read(&kbt->task->mm->mmap_sem);
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+ end_backtrace();
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}
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EXPORT_SYMBOL(tile_show_stack);
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@@ -463,6 +485,8 @@ void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
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int skip = trace->skip;
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int i = 0;
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+ if (!start_backtrace())
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+ goto done;
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if (task == NULL || task == current)
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KBacktraceIterator_init_current(&kbt);
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else
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@@ -476,6 +500,8 @@ void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
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break;
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trace->entries[i++] = kbt.it.pc;
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}
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+ end_backtrace();
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+done:
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trace->nr_entries = i;
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}
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EXPORT_SYMBOL(save_stack_trace_tsk);
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