1 files changed, 141 insertions, 0 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
new file mode 100644
index 000000000000..ab115cd15fdf
--- /dev/null
+++ b/arch/x86/kernel/ftrace.c
@@ -0,0 +1,141 @@
+/*
+ * Code for replacing ftrace calls with jumps.
+ *
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ *
+ * Thanks goes to Ingo Molnar, for suggesting the idea.
+ * Mathieu Desnoyers, for suggesting postponing the modifications.
+ * Arjan van de Ven, for keeping me straight, and explaining to me
+ * the dangers of modifying code on the run.
+ */
+
+#include <linux/spinlock.h>
+#include <linux/hardirq.h>
+#include <linux/ftrace.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/list.h>
+
+#include <asm/alternative.h>
+#include <asm/ftrace.h>
+
+
+/* Long is fine, even if it is only 4 bytes ;-) */
+static long *ftrace_nop;
+
+union ftrace_code_union {
+        char code[MCOUNT_INSN_SIZE];
+        struct {
+                char e8;
+                int offset;
+        } __attribute__((packed));
+};
+
+
+static int notrace ftrace_calc_offset(long ip, long addr)
+{
+        return (int)(addr - ip);
+}
+
+notrace unsigned char *ftrace_nop_replace(void)
+{
+        return (char *)ftrace_nop;
+}
+
+notrace unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
+{
+        static union ftrace_code_union calc;
+
+        calc.e8         = 0xe8;
+        calc.offset     = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
+
+        /*
+         * No locking needed, this must be called via kstop_machine
+         * which in essence is like running on a uniprocessor machine.
+         */
+        return calc.code;
+}
+
+notrace int
+ftrace_modify_code(unsigned long ip, unsigned char *old_code,
+                   unsigned char *new_code)
+{
+        unsigned replaced;
+        unsigned old = *(unsigned *)old_code; /* 4 bytes */
+        unsigned new = *(unsigned *)new_code; /* 4 bytes */
+        unsigned char newch = new_code[4];
+        int faulted = 0;
+
+        /*
+         * 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.
+         */
+        asm volatile (
+                "1: lock\n"
+                "   cmpxchg %3, (%2)\n"
+                "   jnz 2f\n"
+                "   movb %b4, 4(%2)\n"
+                "2:\n"
+                ".section .fixup, \"ax\"\n"
+                "3:     movl $1, %0\n"
+                "       jmp 2b\n"
+                ".previous\n"
+                _ASM_EXTABLE(1b, 3b)
+                : "=r"(faulted), "=a"(replaced)
+                : "r"(ip), "r"(new), "c"(newch),
+                  "0"(faulted), "a"(old)
+                : "memory");
+        sync_core();
+
+        if (replaced != old && replaced != new)
+                faulted = 2;
+
+        return faulted;
+}
+
+notrace int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+        unsigned long ip = (unsigned long)(&ftrace_call);
+        unsigned char old[MCOUNT_INSN_SIZE], *new;
+        int ret;
+
+        memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
+        new = ftrace_call_replace(ip, (unsigned long)func);
+        ret = ftrace_modify_code(ip, old, new);
+
+        return ret;
+}
+
+notrace int ftrace_mcount_set(unsigned long *data)
+{
+        unsigned long ip = (long)(&mcount_call);
+        unsigned long *addr = data;
+        unsigned char old[MCOUNT_INSN_SIZE], *new;
+
+        /*
+         * Replace the mcount stub with a pointer to the
+         * ip recorder function.
+         */
+        memcpy(old, &mcount_call, MCOUNT_INSN_SIZE);
+        new = ftrace_call_replace(ip, *addr);
+        *addr = ftrace_modify_code(ip, old, new);
+
+        return 0;
+}
+
+int __init ftrace_dyn_arch_init(void *data)
+{
+        const unsigned char *const *noptable = find_nop_table();
+
+        /* This is running in kstop_machine */
+
+        ftrace_mcount_set(data);
+
+        ftrace_nop = (unsigned long *)noptable[MCOUNT_INSN_SIZE];
+
+        return 0;
+}