sh: oprofile: Backtrace support.

This patch improves the oprofile support on sh and adds backtrace
support.

Signed-off-by: Dave Peverley <dpeverley@mpc-data.co.uk>
Signed-off-by: Chris Smith <chris.smith@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

2 files changed, 127 insertions, 0 deletions

diff --git a/arch/sh/oprofile/backtrace.c b/arch/sh/oprofile/backtrace.c
new file mode 100644
index 00000000000..418e834654c
--- /dev/null
+++ b/arch/sh/oprofile/backtrace.c
@@ -0,0 +1,118 @@
+/*
+ * SH specific backtracing code for oprofile
+ *
+ * Copyright 2007 STMicroelectronics Ltd.
+ *
+ * Author: Dave Peverley <dpeverley@mpc-data.co.uk>
+ *
+ * Based on ARM oprofile backtrace code by Richard Purdie and in turn, i386
+ * oprofile backtrace code by John Levon, David Smith
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+#include <linux/oprofile.h>
+#include <linux/sched.h>
+#include <linux/kallsyms.h>
+#include <linux/mm.h>
+#include <asm/ptrace.h>
+#include <asm/uaccess.h>
+#include <asm/sections.h>
+
+/* Limit to stop backtracing too far. */
+static int backtrace_limit = 20;
+
+static unsigned long *
+user_backtrace(unsigned long *stackaddr, struct pt_regs *regs)
+{
+        unsigned long buf_stack;
+
+        /* Also check accessibility of address */
+        if (!access_ok(VERIFY_READ, stackaddr, sizeof(unsigned long)))
+                return NULL;
+
+        if (__copy_from_user_inatomic(&buf_stack, stackaddr, sizeof(unsigned long)))
+                return NULL;
+
+        /* Quick paranoia check */
+        if (buf_stack & 3)
+                return NULL;
+
+        oprofile_add_trace(buf_stack);
+
+        stackaddr++;
+
+        return stackaddr;
+}
+
+/*
+ * |             | /\ Higher addresses
+ * |             |
+ * --------------- stack base (address of current_thread_info)
+ * | thread info |
+ * .             .
+ * |    stack    |
+ * --------------- saved regs->regs[15] value if valid
+ * .             .
+ * --------------- struct pt_regs stored on stack (struct pt_regs *)
+ * |             |
+ * .             .
+ * |             |
+ * --------------- ???
+ * |             |
+ * |             | \/ Lower addresses
+ *
+ * Thus, &pt_regs <-> stack base restricts the valid(ish) fp values
+ */
+static int valid_kernel_stack(unsigned long *stackaddr, struct pt_regs *regs)
+{
+        unsigned long stack = (unsigned long)regs;
+        unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE;
+
+        return ((unsigned long)stackaddr > stack) && ((unsigned long)stackaddr < stack_base);
+}
+
+static unsigned long *
+kernel_backtrace(unsigned long *stackaddr, struct pt_regs *regs)
+{
+        unsigned long addr;
+
+        /*
+         * If not a valid kernel address, keep going till we find one
+         * or the SP stops being a valid address.
+         */
+        do {
+                addr = *stackaddr++;
+
+                if (__kernel_text_address(addr)) {
+                        oprofile_add_trace(addr);
+                        break;
+                }
+        } while (valid_kernel_stack(stackaddr, regs));
+
+        return stackaddr;
+}
+
+void sh_backtrace(struct pt_regs * const regs, unsigned int depth)
+{
+        unsigned long *stackaddr;
+
+        /*
+         * Paranoia - clip max depth as we could get lost in the weeds.
+         */
+        if (depth > backtrace_limit)
+                depth = backtrace_limit;
+
+        stackaddr = (unsigned long *)regs->regs[15];
+        if (!user_mode(regs)) {
+                while (depth-- && valid_kernel_stack(stackaddr, regs))
+                        stackaddr = kernel_backtrace(stackaddr, regs);
+
+                return;
+        }
+
+        while (depth-- && (stackaddr != NULL))
+                stackaddr = user_backtrace(stackaddr, regs);
+}
diff --git a/arch/sh/oprofile/common.c b/arch/sh/oprofile/common.c
index a4d8c0c9a63..1d97d64cb95 100644
--- a/arch/sh/oprofile/common.c
+++ b/arch/sh/oprofile/common.c
@@ -27,6 +27,8 @@ static struct op_sh_model *model;
 
 static struct op_counter_config ctr[20];
 
+extern void sh_backtrace(struct pt_regs * const regs, unsigned int depth);
+
 static int op_sh_setup(void)
 {
         /* Pre-compute the values to stuff in the hardware registers.  */
@@ -85,6 +87,13 @@ int __init oprofile_arch_init(struct oprofile_operations *ops)
         struct op_sh_model *lmodel = NULL;
         int ret;
 
+        /*
+         * Always assign the backtrace op. If the counter initialization
+         * fails, we fall back to the timer which will still make use of
+         * this.
+         */
+        ops->backtrace = sh_backtrace;
+
         switch (current_cpu_data.type) {
         /* SH-4 types */
         case CPU_SH7750: