From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001
From: André Fabian Silva Delgado <emulatorman@parabola.nu>
Date: Wed, 5 Aug 2015 17:04:01 -0300
Subject: Initial import

---
 arch/metag/kernel/ftrace.c | 123 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 arch/metag/kernel/ftrace.c

(limited to 'arch/metag/kernel/ftrace.c')

diff --git a/arch/metag/kernel/ftrace.c b/arch/metag/kernel/ftrace.c
new file mode 100644
index 000000000..ed1d68515
--- /dev/null
+++ b/arch/metag/kernel/ftrace.c
@@ -0,0 +1,123 @@
+/*
+ * Copyright (C) 2008 Imagination Technologies Ltd.
+ * Licensed under the GPL
+ *
+ * Dynamic ftrace support.
+ */
+
+#include <linux/ftrace.h>
+#include <linux/io.h>
+#include <linux/uaccess.h>
+
+#include <asm/cacheflush.h>
+
+#define D04_MOVT_TEMPLATE	0x02200005
+#define D04_CALL_TEMPLATE	0xAC200005
+#define D1RTP_MOVT_TEMPLATE	0x03200005
+#define D1RTP_CALL_TEMPLATE	0xAC200006
+
+static const unsigned long NOP[2] = {0xa0fffffe, 0xa0fffffe};
+static unsigned long movt_and_call_insn[2];
+
+static unsigned char *ftrace_nop_replace(void)
+{
+	return (char *)&NOP[0];
+}
+
+static unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr)
+{
+	unsigned long hi16, low16;
+
+	hi16 = (addr & 0xffff0000) >> 13;
+	low16 = (addr & 0x0000ffff) << 3;
+
+	/*
+	 * The compiler makes the call to mcount_wrapper()
+	 * (Meta's wrapper around mcount()) through the register
+	 * D0.4. So whenever we're patching one of those compiler-generated
+	 * calls we also need to go through D0.4. Otherwise use D1RtP.
+	 */
+	if (pc == (unsigned long)&ftrace_call) {
+		writel(D1RTP_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]);
+		writel(D1RTP_CALL_TEMPLATE | low16, &movt_and_call_insn[1]);
+	} else {
+		writel(D04_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]);
+		writel(D04_CALL_TEMPLATE | low16, &movt_and_call_insn[1]);
+	}
+
+	return (unsigned char *)&movt_and_call_insn[0];
+}
+
+static int ftrace_modify_code(unsigned long pc, unsigned char *old_code,
+			      unsigned char *new_code)
+{
+	unsigned char replaced[MCOUNT_INSN_SIZE];
+
+	/*
+	 * Note: Due to modules and __init, code can
+	 *  disappear and change, we need to protect against faulting
+	 *  as well as code changing.
+	 *
+	 * No real locking needed, this code is run through
+	 * kstop_machine.
+	 */
+
+	/* read the text we want to modify */
+	if (probe_kernel_read(replaced, (void *)pc, MCOUNT_INSN_SIZE))
+		return -EFAULT;
+
+	/* Make sure it is what we expect it to be */
+	if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
+		return -EINVAL;
+
+	/* replace the text with the new text */
+	if (probe_kernel_write((void *)pc, new_code, MCOUNT_INSN_SIZE))
+		return -EPERM;
+
+	flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
+
+	return 0;
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+	int ret;
+	unsigned long pc;
+	unsigned char old[MCOUNT_INSN_SIZE], *new;
+
+	pc = (unsigned long)&ftrace_call;
+	memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
+	new = ftrace_call_replace(pc, (unsigned long)func);
+	ret = ftrace_modify_code(pc, old, new);
+
+	return ret;
+}
+
+int ftrace_make_nop(struct module *mod,
+		    struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned char *new, *old;
+	unsigned long ip = rec->ip;
+
+	old = ftrace_call_replace(ip, addr);
+	new = ftrace_nop_replace();
+
+	return ftrace_modify_code(ip, old, new);
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned char *new, *old;
+	unsigned long ip = rec->ip;
+
+	old = ftrace_nop_replace();
+	new = ftrace_call_replace(ip, addr);
+
+	return ftrace_modify_code(ip, old, new);
+}
+
+/* run from kstop_machine */
+int __init ftrace_dyn_arch_init(void)
+{
+	return 0;
+}
-- 
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