[ARM] Add stacktrace support and make oprofile use it

Add support for stacktrace.  Use the new stacktrace code with
oprofile instead of it's version; there's no point having
multiple versions of stacktracing in the kernel.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -67,6 +67,14 @@ config GENERIC_HARDIRQS
 	bool
 	default y
 
+config STACKTRACE_SUPPORT
+	bool
+	default y
+
+config LOCKDEP_SUPPORT
+	bool
+	default y
+
 config TRACE_IRQFLAGS_SUPPORT
 	bool
 	default y

arch/arm/kernel/Makefile

@@ -7,8 +7,8 @@ AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
 # Object file lists.
 
 obj-y		:= compat.o entry-armv.o entry-common.o irq.o \
-		   process.o ptrace.o semaphore.o setup.o signal.o sys_arm.o \
-		   time.o traps.o
+		   process.o ptrace.o semaphore.o setup.o signal.o \
+		   sys_arm.o stacktrace.o time.o traps.o
 
 obj-$(CONFIG_ISA_DMA_API)	+= dma.o
 obj-$(CONFIG_ARCH_ACORN)	+= ecard.o 

arch/arm/kernel/stacktrace.c

@@ -0,0 +1,73 @@
+#include <linux/sched.h>
+#include <linux/stacktrace.h>
+
+#include "stacktrace.h"
+
+int walk_stackframe(unsigned long fp, unsigned long low, unsigned long high,
+		    int (*fn)(struct stackframe *, void *), void *data)
+{
+	struct stackframe *frame;
+
+	do {
+		/*
+		 * Check current frame pointer is within bounds
+		 */
+		if ((fp - 12) < low || fp + 4 >= high)
+			break;
+
+		frame = (struct stackframe *)(fp - 12);
+
+		if (fn(frame, data))
+			break;
+
+		/*
+		 * Update the low bound - the next frame must always
+		 * be at a higher address than the current frame.
+		 */
+		low = fp + 4;
+		fp = frame->fp;
+	} while (fp);
+
+	return 0;
+}
+
+#ifdef CONFIG_STACKTRACE
+struct stack_trace_data {
+	struct stack_trace *trace;
+	unsigned int skip;
+};
+
+static int save_trace(struct stackframe *frame, void *d)
+{
+	struct stack_trace_data *data = d;
+	struct stack_trace *trace = data->trace;
+
+	if (data->skip) {
+		data->skip--;
+		return 0;
+	}
+
+	trace->entries[trace->nr_entries++] = frame->lr;
+
+	return trace->nr_entries >= trace->max_entries;
+}
+
+void save_stack_trace(struct stack_trace *trace, struct task_struct *task)
+{
+	struct stack_trace_data data;
+	unsigned long fp, base;
+
+	data.trace = trace;
+	data.skip = trace->skip;
+
+	if (task) {
+		base = (unsigned long)task_stack_page(task);
+		fp = 0; /* FIXME */
+	} else {
+		base = (unsigned long)task_stack_page(current);
+		asm("mov %0, fp" : "=r" (fp));
+	}
+
+	walk_stackframe(fp, base, base + THREAD_SIZE, save_trace, &data);
+}
+#endif

arch/arm/kernel/stacktrace.h

@@ -0,0 +1,9 @@
+struct stackframe {
+	unsigned long fp;
+	unsigned long sp;
+	unsigned long lr;
+	unsigned long pc;
+};
+
+int walk_stackframe(unsigned long fp, unsigned long low, unsigned long high,
+		    int (*fn)(struct stackframe *, void *), void *data);

arch/arm/oprofile/backtrace.c

@@ -19,6 +19,19 @@
 #include <asm/ptrace.h>
 #include <asm/uaccess.h>
 
+#include "../kernel/stacktrace.h"
+
+static int report_trace(struct stackframe *frame, void *d)
+{
+	unsigned int *depth = d;
+
+	if (*depth) {
+		oprofile_add_trace(frame->lr);
+		(*depth)--;
+	}
+
+	return *depth == 0;
+}
 
 /*
  * The registers we're interested in are at the end of the variable
@@ -32,21 +45,6 @@ struct frame_tail {
 	unsigned long lr;
 } __attribute__((packed));
 
-
-#ifdef CONFIG_FRAME_POINTER
-static struct frame_tail* kernel_backtrace(struct frame_tail *tail)
-{
-	oprofile_add_trace(tail->lr);
-
-	/* frame pointers should strictly progress back up the stack
-	 * (towards higher addresses) */
-	if (tail >= tail->fp)
-		return NULL;
-
-	return tail->fp-1;
-}
-#endif
-
 static struct frame_tail* user_backtrace(struct frame_tail *tail)
 {
 	struct frame_tail buftail[2];
@@ -67,47 +65,14 @@ static struct frame_tail* user_backtrace(struct frame_tail *tail)
 	return buftail[0].fp-1;
 }
 
-/*
- * |             | /\ Higher addresses
- * |             |
- * --------------- stack base (address of current_thread_info)
- * | thread info |
- * .             .
- * |    stack    |
- * --------------- saved regs->ARM_fp value if valid (frame_tail address)
- * .             .
- * --------------- struct pt_regs stored on stack (struct pt_regs *)
- * |             |
- * .             .
- * |             |
- * --------------- %esp
- * |             |
- * |             | \/ Lower addresses
- *
- * Thus, &pt_regs <-> stack base restricts the valid(ish) fp values
- */
-static int valid_kernel_stack(struct frame_tail *tail, struct pt_regs *regs)
-{
-	unsigned long tailaddr = (unsigned long)tail;
-	unsigned long stack = (unsigned long)regs;
-	unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE;
-
-	return (tailaddr > stack) && (tailaddr < stack_base);
-}
-
 void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
 {
-	struct frame_tail *tail;
-
-	tail = ((struct frame_tail *) regs->ARM_fp) - 1;
+	struct frame_tail *tail = ((struct frame_tail *) regs->ARM_fp) - 1;
 
 	if (!user_mode(regs)) {
-
-#ifdef CONFIG_FRAME_POINTER
-		while (depth-- && tail && valid_kernel_stack(tail, regs)) {
-			tail = kernel_backtrace(tail);
-		}
-#endif
+		unsigned long base = ((unsigned long)regs) & ~(THREAD_SIZE - 1);
+		walk_stackframe(regs->ARM_fp, base, base + THREAD_SIZE,
+				report_trace, &depth);
 		return;
 	}