5 files changed, 154 insertions, 1 deletions

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index d203dbfa8037..af6940c5b272 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -7,6 +7,8 @@ config MIPS
         select HAVE_ARCH_KGDB
         select HAVE_FUNCTION_TRACER
         select HAVE_FUNCTION_TRACE_MCOUNT_TEST
+        select HAVE_DYNAMIC_FTRACE
+        select HAVE_FTRACE_MCOUNT_RECORD
         # Horrible source of confusion.  Die, die, die ...
         select EMBEDDED
         select RTC_LIB if !MACH_LOONGSON
diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h
index 5f8ebcf9fa61..7094a40b96d8 100644
--- a/arch/mips/include/asm/ftrace.h
+++ b/arch/mips/include/asm/ftrace.h
@@ -19,6 +19,15 @@
 extern void _mcount(void);
 #define mcount _mcount
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+static inline unsigned long ftrace_call_adjust(unsigned long addr)
+{
+        return addr;
+}
+
+struct dyn_arch_ftrace {
+};
+#endif /*  CONFIG_DYNAMIC_FTRACE */
 #endif /* __ASSEMBLY__ */
 #endif /* CONFIG_FUNCTION_TRACER */
 #endif /* _ASM_MIPS_FTRACE_H */
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 1340ba3dd38d..8dda21463226 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -11,6 +11,7 @@ obj-y		+= cpu-probe.o branch.o entry.o genex.o irq.o process.o \
                    time.o topology.o traps.o unaligned.o watch.o
 
 ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_ftrace.o = -pg
 CFLAGS_REMOVE_early_printk.o = -pg
 endif
 
@@ -31,7 +32,7 @@ obj-$(CONFIG_SYNC_R4K)		+= sync-r4k.o
 obj-$(CONFIG_STACKTRACE)        += stacktrace.o
 obj-$(CONFIG_MODULES)           += mips_ksyms.o module.o
 
-obj-$(CONFIG_FUNCTION_TRACER)   += mcount.o
+obj-$(CONFIG_FUNCTION_TRACER)   += mcount.o ftrace.o
 
 obj-$(CONFIG_CPU_LOONGSON2)     += r4k_fpu.o r4k_switch.o
 obj-$(CONFIG_CPU_MIPS32)        += r4k_fpu.o r4k_switch.o
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
new file mode 100644
index 000000000000..5459a7838370
--- /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 */
diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
index cbb45edad464..ffc425979d4f 100644
--- a/arch/mips/kernel/mcount.S
+++ b/arch/mips/kernel/mcount.S
@@ -58,6 +58,33 @@
          move ra, AT
         .endm
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+NESTED(ftrace_caller, PT_SIZE, ra)
+        .globl _mcount
+_mcount:
+        b       ftrace_stub
+         nop
+        lw      t0, function_trace_stop
+        bnez    t0, ftrace_stub
+         nop
+
+        MCOUNT_SAVE_REGS
+
+        move    a0, ra          /* arg1: next ip, selfaddr */
+        .globl ftrace_call
+ftrace_call:
+        nop     /* a placeholder for the call to a real tracing function */
+         move   a1, AT          /* arg2: the caller's next ip, parent */
+
+        MCOUNT_RESTORE_REGS
+        .globl ftrace_stub
+ftrace_stub:
+        RETURN_BACK
+        END(ftrace_caller)
+
+#else   /* ! CONFIG_DYNAMIC_FTRACE */
+
 NESTED(_mcount, PT_SIZE, ra)
         lw      t0, function_trace_stop
         bnez    t0, ftrace_stub
@@ -82,5 +109,7 @@ ftrace_stub:
         RETURN_BACK
         END(_mcount)
 
+#endif  /* ! CONFIG_DYNAMIC_FTRACE */
+
         .set at
         .set reorder