microblaze: ftrace: Add dynamic trace support

With dynamic function tracer, by default, _mcount is defined as an
"empty" function, it returns directly without any more action. When
enabling it in user-space, it will jump to a real tracing
function(ftrace_caller), and do the real job for us.

Differ from the static function tracer, dynamic function tracer provides
two functions ftrace_make_call()/ftrace_make_nop() to enable/disable the
tracing of some indicated kernel functions(set_ftrace_filter).

In the kernel version, there is only one "_mcount" string for every
kernel function, so, we just need to match this one in mcount_regex of
scripts/recordmcount.pl.

For more information please look at code and Documentation/trace folder.

Steven ACK that scripts/recordmcount.pl part.

Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Michal Simek <monstr@monstr.eu>

5 files changed, 178 insertions, 1 deletions

diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index cccf3adfae50..102d73aa1063 100644
--- a/arch/microblaze/Kconfig
+++ b/arch/microblaze/Kconfig
@@ -8,6 +8,8 @@ config MICROBLAZE
         select HAVE_LMB
         select HAVE_FUNCTION_TRACER
         select HAVE_FUNCTION_TRACE_MCOUNT_TEST
+        select HAVE_DYNAMIC_FTRACE
+        select HAVE_FTRACE_MCOUNT_RECORD
         select USB_ARCH_HAS_EHCI
         select ARCH_WANT_OPTIONAL_GPIOLIB
 
diff --git a/arch/microblaze/include/asm/ftrace.h b/arch/microblaze/include/asm/ftrace.h
index 22beec58c021..fd2fa2eca62f 100644
--- a/arch/microblaze/include/asm/ftrace.h
+++ b/arch/microblaze/include/asm/ftrace.h
@@ -11,5 +11,16 @@ extern void _mcount(void);
 extern void ftrace_call_graph(void);
 #endif
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+/* reloction of mcount call site is the same as the address */
+static inline unsigned long ftrace_call_adjust(unsigned long addr)
+{
+        return addr;
+}
+
+struct dyn_arch_ftrace {
+};
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
 #endif /* CONFIG_FUNCTION_TRACER */
 #endif /* _ASM_MICROBLAZE_FTRACE */
diff --git a/arch/microblaze/kernel/Makefile b/arch/microblaze/kernel/Makefile
index d5ee3264cd7d..b07594eccf9b 100644
--- a/arch/microblaze/kernel/Makefile
+++ b/arch/microblaze/kernel/Makefile
@@ -27,6 +27,6 @@ obj-$(CONFIG_HEART_BEAT)	+= heartbeat.o
 obj-$(CONFIG_MODULES)           += microblaze_ksyms.o module.o
 obj-$(CONFIG_MMU)               += misc.o
 obj-$(CONFIG_STACKTRACE)        += stacktrace.o
-obj-$(CONFIG_FUNCTION_TRACER)   += mcount.o
+obj-$(CONFIG_FUNCTION_TRACER)   += ftrace.o mcount.o
 
 obj-y   += entry$(MMU).o
diff --git a/arch/microblaze/kernel/ftrace.c b/arch/microblaze/kernel/ftrace.c
new file mode 100644
index 000000000000..c1889b101cb8
--- /dev/null
+++ b/arch/microblaze/kernel/ftrace.c
@@ -0,0 +1,151 @@
+/*
+ * Ftrace support for Microblaze.
+ *
+ * Copyright (C) 2009 Michal Simek <monstr@monstr.eu>
+ * Copyright (C) 2009 PetaLogix
+ *
+ * Based on MIPS and PowerPC ftrace code
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <asm/cacheflush.h>
+#include <linux/ftrace.h>
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+/* save value to addr - it is save to do it in asm */
+static int ftrace_modify_code(unsigned long addr, unsigned int value)
+{
+        int faulted = 0;
+
+        __asm__ __volatile__("  1:      swi     %2, %1, 0;              \
+                                        addik   %0, r0, 0;              \
+                                2:                                      \
+                                        .section .fixup, \"ax\";        \
+                                3:      brid    2b;                     \
+                                        addik   %0, r0, 1;              \
+                                        .previous;                      \
+                                        .section __ex_table,\"a\";      \
+                                        .word   1b,3b;                  \
+                                        .previous;"                     \
+                                : "=r" (faulted)
+                                : "r" (addr), "r" (value)
+        );
+
+        if (unlikely(faulted))
+                return -EFAULT;
+
+        return 0;
+}
+
+#define MICROBLAZE_NOP 0x80000000
+#define MICROBLAZE_BRI 0xb800000C
+
+static unsigned int recorded; /* if save was or not */
+static unsigned int imm; /* saving whole imm instruction */
+
+/* There are two approaches howto solve ftrace_make nop function - look below */
+#undef USE_FTRACE_NOP
+
+#ifdef USE_FTRACE_NOP
+static unsigned int bralid; /* saving whole bralid instruction */
+#endif
+
+int ftrace_make_nop(struct module *mod,
+                        struct dyn_ftrace *rec, unsigned long addr)
+{
+        /* we have this part of code which we are working with
+         * b000c000        imm     -16384
+         * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
+         * 80000000        or      r0, r0, r0
+         *
+         * The first solution (!USE_FTRACE_NOP-could be called branch solution)
+         * b000c000        bri  12 (0xC - jump to any other instruction)
+         * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
+         * 80000000        or      r0, r0, r0
+         * any other instruction
+         *
+         * The second solution (USE_FTRACE_NOP) - no jump just nops
+         * 80000000        or      r0, r0, r0
+         * 80000000        or      r0, r0, r0
+         * 80000000        or      r0, r0, r0
+         */
+        int ret = 0;
+
+        if (recorded == 0) {
+                recorded = 1;
+                imm = *(unsigned int *)rec->ip;
+                pr_debug("%s: imm:0x%x\n", __func__, imm);
+#ifdef USE_FTRACE_NOP
+                bralid = *(unsigned int *)(rec->ip + 4);
+                pr_debug("%s: bralid 0x%x\n", __func__, bralid);
+#endif /* USE_FTRACE_NOP */
+        }
+
+#ifdef USE_FTRACE_NOP
+        ret = ftrace_modify_code(rec->ip, MICROBLAZE_NOP);
+        ret += ftrace_modify_code(rec->ip + 4, MICROBLAZE_NOP);
+#else /* USE_FTRACE_NOP */
+        ret = ftrace_modify_code(rec->ip, MICROBLAZE_BRI);
+#endif /* USE_FTRACE_NOP */
+        return ret;
+}
+
+static int ret_addr; /* initialized as 0 by default */
+
+/* I believe that first is called ftrace_make_nop before this function */
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+        int ret;
+        ret_addr = addr; /* saving where the barrier jump is */
+        pr_debug("%s: addr:0x%x, rec->ip: 0x%x, imm:0x%x\n",
+                __func__, (unsigned int)addr, (unsigned int)rec->ip, imm);
+        ret = ftrace_modify_code(rec->ip, imm);
+#ifdef USE_FTRACE_NOP
+        pr_debug("%s: bralid:0x%x\n", __func__, bralid);
+        ret += ftrace_modify_code(rec->ip + 4, bralid);
+#endif /* USE_FTRACE_NOP */
+        return ret;
+}
+
+int __init ftrace_dyn_arch_init(void *data)
+{
+        /* The return code is retured via data */
+        *(unsigned long *)data = 0;
+
+        return 0;
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+        unsigned long ip = (unsigned long)(&ftrace_call);
+        unsigned int upper = (unsigned int)func;
+        unsigned int lower = (unsigned int)func;
+        int ret = 0;
+
+        /* create proper saving to ftrace_call poll */
+        upper = 0xb0000000 + (upper >> 16); /* imm func_upper */
+        lower = 0x32800000 + (lower & 0xFFFF); /* addik r20, r0, func_lower */
+
+        pr_debug("%s: func=0x%x, ip=0x%x, upper=0x%x, lower=0x%x\n",
+                __func__, (unsigned int)func, (unsigned int)ip, upper, lower);
+
+        /* save upper and lower code */
+        ret = ftrace_modify_code(ip, upper);
+        ret += ftrace_modify_code(ip + 4, lower);
+
+        /* We just need to remove the rtsd r15, 8 by NOP */
+        BUG_ON(!ret_addr);
+        if (ret_addr)
+                ret += ftrace_modify_code(ret_addr, MICROBLAZE_NOP);
+        else
+                ret = 1; /* fault */
+
+        /* All changes are done - lets do caches consistent */
+        flush_icache();
+        return ret;
+}
+
+#endif /* CONFIG_DYNAMIC_FTRACE */
diff --git a/arch/microblaze/kernel/mcount.S b/arch/microblaze/kernel/mcount.S
index 97eef3eea944..30aaf8fb55b2 100644
--- a/arch/microblaze/kernel/mcount.S
+++ b/arch/microblaze/kernel/mcount.S
@@ -83,6 +83,12 @@ ENTRY(ftrace_stub)
         nop;
 
 ENTRY(_mcount)
+#ifdef CONFIG_DYNAMIC_FTRACE
+ENTRY(ftrace_caller)
+        /* MS: It is just barrier which is removed from C code */
+        rtsd    r15, 8
+        nop
+#endif /* CONFIG_DYNAMIC_FTRACE */
         SAVE_REGS
         swi     r15, r1, 0;
         /* MS: HAVE_FUNCTION_TRACE_MCOUNT_TEST begin of checking */
@@ -90,12 +96,19 @@ ENTRY(_mcount)
         bneid   r5, end;
         nop;
         /* MS: HAVE_FUNCTION_TRACE_MCOUNT_TEST end of checking */
+#ifndef CONFIG_DYNAMIC_FTRACE
         /* MS: test function trace if is taken or not */
         lwi     r20, r0, ftrace_trace_function;
         addik   r6, r0, ftrace_stub;
         cmpu    r5, r20, r6; /* ftrace_trace_function != ftrace_stub */
         beqid   r5, end; /* MS: not taken -> jump over */
         nop;
+#else /* CONFIG_DYNAMIC_FTRACE */
+NOALIGN_ENTRY(ftrace_call)
+/* instruction for setup imm FUNC_part1, addik r20, r0, FUNC_part2 */
+        nop
+        nop
+#endif /* CONFIG_DYNAMIC_FTRACE */
 /* static normal trace */
         lwi     r6, r1, 120; /* MS: load parent addr */
         addik   r5, r15, 0; /* MS: load current function addr */