1 files changed, 112 insertions, 0 deletions

diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
new file mode 100644
index 00000000000..5459a783837
--- /dev/null
+++ b/arch/mips/kernel/ftrace.c
@@ -0,0 +1,112 @@
+/*
+ * Code for replacing ftrace calls with jumps.
+ *
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ * Copyright (C) 2009 DSLab, Lanzhou University, China
+ * Author: Wu Zhangjin <wuzj@lemote.com>
+ *
+ * Thanks goes to Steven Rostedt for writing the original x86 version.
+ */
+
+#include <linux/uaccess.h>
+#include <linux/init.h>
+#include <linux/ftrace.h>
+
+#include <asm/cacheflush.h>
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+#define JAL 0x0c000000          /* jump & link: ip --> ra, jump to target */
+#define ADDR_MASK 0x03ffffff    /*  op_code|addr : 31...26|25 ....0 */
+#define jump_insn_encode(op_code, addr) \
+        ((unsigned int)((op_code) | (((addr) >> 2) & ADDR_MASK)))
+
+static unsigned int ftrace_nop = 0x00000000;
+
+static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
+{
+        *(unsigned int *)ip = new_code;
+
+        flush_icache_range(ip, ip + 8);
+
+        return 0;
+}
+
+static int lui_v1;
+static int jal_mcount;
+
+int ftrace_make_nop(struct module *mod,
+                    struct dyn_ftrace *rec, unsigned long addr)
+{
+        unsigned int new;
+        unsigned long ip = rec->ip;
+
+        /* We have compiled module with -mlong-calls, but compiled the kernel
+         * without it, we need to cope with them respectively. */
+        if (ip & 0x40000000) {
+                /* record it for ftrace_make_call */
+                if (lui_v1 == 0)
+                        lui_v1 = *(unsigned int *)ip;
+
+                /* lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
+                 * addiu v1, v1, low_16bit_of_mcount
+                 * move at, ra
+                 * jalr v1
+                 * nop
+                 *                                   1f: (ip + 12)
+                 */
+                new = 0x10000004;
+        } else {
+                /* record/calculate it for ftrace_make_call */
+                if (jal_mcount == 0) {
+                        /* We can record it directly like this:
+                         *     jal_mcount = *(unsigned int *)ip;
+                         * Herein, jump over the first two nop instructions */
+                        jal_mcount = jump_insn_encode(JAL, (MCOUNT_ADDR + 8));
+                }
+
+                /* move at, ra
+                 * jalr v1              --> nop
+                 */
+                new = ftrace_nop;
+        }
+        return ftrace_modify_code(ip, new);
+}
+
+static int modified;    /* initialized as 0 by default */
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+        unsigned int new;
+        unsigned long ip = rec->ip;
+
+        /* We just need to remove the "b ftrace_stub" at the fist time! */
+        if (modified == 0) {
+                modified = 1;
+                ftrace_modify_code(addr, ftrace_nop);
+        }
+        /* ip, module: 0xc0000000, kernel: 0x80000000 */
+        new = (ip & 0x40000000) ? lui_v1 : jal_mcount;
+
+        return ftrace_modify_code(ip, new);
+}
+
+#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+        unsigned int new;
+
+        new = jump_insn_encode(JAL, (unsigned long)func);
+
+        return ftrace_modify_code(FTRACE_CALL_IP, new);
+}
+
+int __init ftrace_dyn_arch_init(void *data)
+{
+        /* The return code is retured via data */
+        *(unsigned long *)data = 0;
+
+        return 0;
+}
+#endif                          /* CONFIG_DYNAMIC_FTRACE */