1 files changed, 131 insertions, 0 deletions

diff --git a/kernel/arch/ia64/oprofile/backtrace.c b/kernel/arch/ia64/oprofile/backtrace.c
new file mode 100644
index 000000000..6a219a946
--- /dev/null
+++ b/kernel/arch/ia64/oprofile/backtrace.c
@@ -0,0 +1,131 @@
+/**
+ * @file backtrace.c
+ *
+ * @remark Copyright 2004 Silicon Graphics Inc.  All Rights Reserved.
+ * @remark Read the file COPYING
+ *
+ * @author Greg Banks <gnb@melbourne.sgi.com>
+ * @author Keith Owens <kaos@melbourne.sgi.com>
+ * Based on work done for the ia64 port of the SGI kernprof patch, which is
+ *    Copyright (c) 2003-2004 Silicon Graphics Inc.  All Rights Reserved.
+ */
+
+#include <linux/oprofile.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <asm/ptrace.h>
+
+/*
+ * For IA64 we need to perform a complex little dance to get both
+ * the struct pt_regs and a synthetic struct switch_stack in place
+ * to allow the unwind code to work.  This dance requires our unwind
+ * using code to be called from a function called from unw_init_running().
+ * There we only get a single void* data pointer, so use this struct
+ * to hold all the data we need during the unwind.
+ */
+typedef struct
+{
+	unsigned int depth;
+	struct pt_regs *regs;
+	struct unw_frame_info frame;
+	unsigned long *prev_pfs_loc;	/* state for WAR for old spinlock ool code */
+} ia64_backtrace_t;
+
+/* Returns non-zero if the PC is in the Interrupt Vector Table */
+static __inline__ int in_ivt_code(unsigned long pc)
+{
+	extern char ia64_ivt[];
+	return (pc >= (u_long)ia64_ivt && pc < (u_long)ia64_ivt+32768);
+}
+
+/*
+ * Unwind to next stack frame.
+ */
+static __inline__ int next_frame(ia64_backtrace_t *bt)
+{
+	/*
+	 * Avoid unsightly console message from unw_unwind() when attempting
+	 * to unwind through the Interrupt Vector Table which has no unwind
+	 * information.
+	 */
+	if (in_ivt_code(bt->frame.ip))
+		return 0;
+
+	/*
+	 * WAR for spinlock contention from leaf functions.  ia64_spinlock_contention_pre3_4
+	 * has ar.pfs == r0.  Leaf functions do not modify ar.pfs so ar.pfs remains
+	 * as 0, stopping the backtrace.  Record the previous ar.pfs when the current
+	 * IP is in ia64_spinlock_contention_pre3_4 then unwind, if pfs_loc has not changed
+	 * after unwind then use pt_regs.ar_pfs which is where the real ar.pfs is for
+	 * leaf functions.
+	 */
+	if (bt->prev_pfs_loc && bt->regs && bt->frame.pfs_loc == bt->prev_pfs_loc)
+		bt->frame.pfs_loc = &bt->regs->ar_pfs;
+	bt->prev_pfs_loc = NULL;
+
+	return unw_unwind(&bt->frame) == 0;
+}
+
+
+static void do_ia64_backtrace(struct unw_frame_info *info, void *vdata)
+{
+	ia64_backtrace_t *bt = vdata;
+	struct switch_stack *sw;
+	int count = 0;
+	u_long pc, sp;
+
+	sw = (struct switch_stack *)(info+1);
+	/* padding from unw_init_running */
+	sw = (struct switch_stack *)(((unsigned long)sw + 15) & ~15);
+
+	unw_init_frame_info(&bt->frame, current, sw);
+
+	/* skip over interrupt frame and oprofile calls */
+	do {
+		unw_get_sp(&bt->frame, &sp);
+		if (sp >= (u_long)bt->regs)
+			break;
+		if (!next_frame(bt))
+			return;
+	} while (count++ < 200);
+
+	/* finally, grab the actual sample */
+	while (bt->depth-- && next_frame(bt)) {
+		unw_get_ip(&bt->frame, &pc);
+		oprofile_add_trace(pc);
+		if (unw_is_intr_frame(&bt->frame)) {
+			/*
+			 * Interrupt received on kernel stack; this can
+			 * happen when timer interrupt fires while processing
+			 * a softirq from the tail end of a hardware interrupt
+			 * which interrupted a system call.  Don't laugh, it
+			 * happens!  Splice the backtrace into two parts to
+			 * avoid spurious cycles in the gprof output.
+			 */
+			/* TODO: split rather than drop the 2nd half */
+			break;
+		}
+	}
+}
+
+void
+ia64_backtrace(struct pt_regs * const regs, unsigned int depth)
+{
+	ia64_backtrace_t bt;
+	unsigned long flags;
+
+	/*
+	 * On IA64 there is little hope of getting backtraces from
+	 * user space programs -- the problems of getting the unwind
+	 * information from arbitrary user programs are extreme.
+	 */
+	if (user_mode(regs))
+		return;
+
+	bt.depth = depth;
+	bt.regs = regs;
+	bt.prev_pfs_loc = NULL;
+	local_irq_save(flags);
+	unw_init_running(do_ia64_backtrace, &bt);
+	local_irq_restore(flags);
+}