[PATCH] lockdep: stacktrace subsystem, i386 support

Framework to generate and save stacktraces quickly, without printing anything
to the console.  i386 support.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/Kconfig

@@ -18,6 +18,10 @@ config GENERIC_TIME
 	bool
 	default y
 
+config STACKTRACE_SUPPORT
+	bool
+	default y
+
 config SEMAPHORE_SLEEPERS
 	bool
 	default y

arch/i386/kernel/Makefile

@@ -9,6 +9,7 @@ obj-y	:= process.o semaphore.o signal.o entry.o traps.o irq.o \
 		pci-dma.o i386_ksyms.o i387.o bootflag.o \
 		quirks.o i8237.o topology.o alternative.o i8253.o tsc.o
 
+obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
 obj-y				+= cpu/
 obj-y				+= acpi/
 obj-$(CONFIG_X86_BIOS_REBOOT)	+= reboot.o

arch/i386/kernel/stacktrace.c

@@ -0,0 +1,98 @@
+/*
+ * arch/i386/kernel/stacktrace.c
+ *
+ * Stack trace management functions
+ *
+ *  Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ */
+#include <linux/sched.h>
+#include <linux/stacktrace.h>
+
+static inline int valid_stack_ptr(struct thread_info *tinfo, void *p)
+{
+	return	p > (void *)tinfo &&
+		p < (void *)tinfo + THREAD_SIZE - 3;
+}
+
+/*
+ * Save stack-backtrace addresses into a stack_trace buffer:
+ */
+static inline unsigned long
+save_context_stack(struct stack_trace *trace, unsigned int skip,
+		   struct thread_info *tinfo, unsigned long *stack,
+		   unsigned long ebp)
+{
+	unsigned long addr;
+
+#ifdef CONFIG_FRAME_POINTER
+	while (valid_stack_ptr(tinfo, (void *)ebp)) {
+		addr = *(unsigned long *)(ebp + 4);
+		if (!skip)
+			trace->entries[trace->nr_entries++] = addr;
+		else
+			skip--;
+		if (trace->nr_entries >= trace->max_entries)
+			break;
+		/*
+		 * break out of recursive entries (such as
+		 * end_of_stack_stop_unwind_function):
+	 	 */
+		if (ebp == *(unsigned long *)ebp)
+			break;
+
+		ebp = *(unsigned long *)ebp;
+	}
+#else
+	while (valid_stack_ptr(tinfo, stack)) {
+		addr = *stack++;
+		if (__kernel_text_address(addr)) {
+			if (!skip)
+				trace->entries[trace->nr_entries++] = addr;
+			else
+				skip--;
+			if (trace->nr_entries >= trace->max_entries)
+				break;
+		}
+	}
+#endif
+
+	return ebp;
+}
+
+/*
+ * Save stack-backtrace addresses into a stack_trace buffer.
+ * If all_contexts is set, all contexts (hardirq, softirq and process)
+ * are saved. If not set then only the current context is saved.
+ */
+void save_stack_trace(struct stack_trace *trace,
+		      struct task_struct *task, int all_contexts,
+		      unsigned int skip)
+{
+	unsigned long ebp;
+	unsigned long *stack = &ebp;
+
+	WARN_ON(trace->nr_entries || !trace->max_entries);
+
+	if (!task || task == current) {
+		/* Grab ebp right from our regs: */
+		asm ("movl %%ebp, %0" : "=r" (ebp));
+	} else {
+		/* ebp is the last reg pushed by switch_to(): */
+		ebp = *(unsigned long *) task->thread.esp;
+	}
+
+	while (1) {
+		struct thread_info *context = (struct thread_info *)
+				((unsigned long)stack & (~(THREAD_SIZE - 1)));
+
+		ebp = save_context_stack(trace, skip, context, stack, ebp);
+		stack = (unsigned long *)context->previous_esp;
+		if (!all_contexts || !stack ||
+				trace->nr_entries >= trace->max_entries)
+			break;
+		trace->entries[trace->nr_entries++] = ULONG_MAX;
+		if (trace->nr_entries >= trace->max_entries)
+			break;
+	}
+}
+