[S390] ftrace: add dynamic ftrace support

Dynamic ftrace support for s390.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

6 files changed, 236 insertions, 27 deletions

diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile
index 0657de7944fe..ce172bfaab8a 100644
--- a/arch/s390/kernel/Makefile
+++ b/arch/s390/kernel/Makefile
@@ -7,6 +7,10 @@ ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_early.o = -pg
 endif
 
+ifdef CONFIG_DYNAMIC_FTRACE
+CFLAGS_REMOVE_ftrace.o = -pg
+endif
+
 #
 # Passing null pointers is ok for smp code, since we access the lowcore here.
 #
@@ -41,6 +45,7 @@ obj-$(CONFIG_COMPAT)		+= compat_linux.o compat_signal.o \
 obj-$(CONFIG_STACKTRACE)        += stacktrace.o
 obj-$(CONFIG_KPROBES)           += kprobes.o
 obj-$(CONFIG_FUNCTION_TRACER)   += mcount.o
+obj-$(CONFIG_DYNAMIC_FTRACE)    += ftrace.o
 
 # Kexec part
 S390_KEXEC_OBJS := machine_kexec.o crash.o
diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index cf09948faad6..fb263736826c 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -11,6 +11,7 @@
 #include <linux/errno.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
+#include <linux/ftrace.h>
 #include <linux/lockdep.h>
 #include <linux/module.h>
 #include <linux/pfn.h>
@@ -410,5 +411,8 @@ void __init startup_init(void)
         sclp_facilities_detect();
         detect_memory_layout(memory_chunk);
         S390_lowcore.machine_flags = machine_flags;
+#ifdef CONFIG_DYNAMIC_FTRACE
+        S390_lowcore.ftrace_func = (unsigned long)ftrace_caller;
+#endif
         lockdep_on();
 }
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
new file mode 100644
index 000000000000..0b81a784e039
--- /dev/null
+++ b/arch/s390/kernel/ftrace.c
@@ -0,0 +1,132 @@
+/*
+ * Dynamic function tracer architecture backend.
+ *
+ * Copyright IBM Corp. 2009
+ *
+ *   Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
+ *
+ */
+
+#include <linux/uaccess.h>
+#include <linux/ftrace.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <asm/lowcore.h>
+
+void ftrace_disable_code(void);
+void ftrace_call_code(void);
+void ftrace_nop_code(void);
+
+#define FTRACE_INSN_SIZE 4
+
+#ifdef CONFIG_64BIT
+
+asm(
+        "       .align  4\n"
+        "ftrace_disable_code:\n"
+        "       j       0f\n"
+        "       .word   0x0024\n"
+        "       lg      %r1,"__stringify(__LC_FTRACE_FUNC)"\n"
+        "       basr    %r14,%r1\n"
+        "       lg      %r14,8(15)\n"
+        "       lgr     %r0,%r0\n"
+        "0:\n");
+
+asm(
+        "       .align  4\n"
+        "ftrace_nop_code:\n"
+        "       j       .+"__stringify(MCOUNT_INSN_SIZE)"\n");
+
+asm(
+        "       .align  4\n"
+        "ftrace_call_code:\n"
+        "       stg     %r14,8(%r15)\n");
+
+#else /* CONFIG_64BIT */
+
+asm(
+        "       .align  4\n"
+        "ftrace_disable_code:\n"
+        "       j       0f\n"
+        "       l       %r1,"__stringify(__LC_FTRACE_FUNC)"\n"
+        "       basr    %r14,%r1\n"
+        "       l       %r14,4(%r15)\n"
+        "       j       0f\n"
+        "       bcr     0,%r7\n"
+        "       bcr     0,%r7\n"
+        "       bcr     0,%r7\n"
+        "       bcr     0,%r7\n"
+        "       bcr     0,%r7\n"
+        "       bcr     0,%r7\n"
+        "0:\n");
+
+asm(
+        "       .align  4\n"
+        "ftrace_nop_code:\n"
+        "       j       .+"__stringify(MCOUNT_INSN_SIZE)"\n");
+
+asm(
+        "       .align  4\n"
+        "ftrace_call_code:\n"
+        "       st      %r14,4(%r15)\n");
+
+#endif /* CONFIG_64BIT */
+
+static int ftrace_modify_code(unsigned long ip,
+                              void *old_code, int old_size,
+                              void *new_code, int new_size)
+{
+        unsigned char replaced[MCOUNT_INSN_SIZE];
+
+        /*
+         * Note: Due to modules code can disappear and change.
+         *  We need to protect against faulting as well as code
+         *  changing. We do this by using the probe_kernel_*
+         *  functions.
+         *  This however is just a simple sanity check.
+         */
+        if (probe_kernel_read(replaced, (void *)ip, old_size))
+                return -EFAULT;
+        if (memcmp(replaced, old_code, old_size) != 0)
+                return -EINVAL;
+        if (probe_kernel_write((void *)ip, new_code, new_size))
+                return -EPERM;
+        return 0;
+}
+
+static int ftrace_make_initial_nop(struct module *mod, struct dyn_ftrace *rec,
+                                   unsigned long addr)
+{
+        return ftrace_modify_code(rec->ip,
+                                  ftrace_call_code, FTRACE_INSN_SIZE,
+                                  ftrace_disable_code, MCOUNT_INSN_SIZE);
+}
+
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
+                    unsigned long addr)
+{
+        if (addr == MCOUNT_ADDR)
+                return ftrace_make_initial_nop(mod, rec, addr);
+        return ftrace_modify_code(rec->ip,
+                                  ftrace_call_code, FTRACE_INSN_SIZE,
+                                  ftrace_nop_code, FTRACE_INSN_SIZE);
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+        return ftrace_modify_code(rec->ip,
+                                  ftrace_nop_code, FTRACE_INSN_SIZE,
+                                  ftrace_call_code, FTRACE_INSN_SIZE);
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+        ftrace_dyn_func = (unsigned long)func;
+        return 0;
+}
+
+int __init ftrace_dyn_arch_init(void *data)
+{
+        *(unsigned long *)data = 0;
+        return 0;
+}
diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S
index 80641224a095..de274996f640 100644
--- a/arch/s390/kernel/mcount.S
+++ b/arch/s390/kernel/mcount.S
@@ -1,5 +1,5 @@
 /*
- * Copyright IBM Corp. 2008
+ * Copyright IBM Corp. 2008,2009
  *
  *   Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
  *
@@ -7,36 +7,46 @@
 
 #include <asm/asm-offsets.h>
 
-#ifndef CONFIG_64BIT
-.globl _mcount
+        .globl ftrace_stub
+ftrace_stub:
+        br      %r14
+
+#ifdef CONFIG_64BIT
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+        .globl _mcount
 _mcount:
-        stm     %r0,%r5,8(%r15)
-        st      %r14,56(%r15)
-        lr      %r1,%r15
-        ahi     %r15,-96
-        l       %r3,100(%r15)
-        la      %r2,0(%r14)
-        st      %r1,__SF_BACKCHAIN(%r15)
-        la      %r3,0(%r3)
-        bras    %r14,0f
-        .long   ftrace_trace_function
-0:      l       %r14,0(%r14)
-        l       %r14,0(%r14)
-        basr    %r14,%r14
-        ahi     %r15,96
-        lm      %r0,%r5,8(%r15)
-        l       %r14,56(%r15)
         br      %r14
 
-.globl ftrace_stub
-ftrace_stub:
+        .globl ftrace_caller
+ftrace_caller:
+        stmg    %r2,%r5,32(%r15)
+        stg     %r14,112(%r15)
+        lgr     %r1,%r15
+        aghi    %r15,-160
+        stg     %r1,__SF_BACKCHAIN(%r15)
+        lgr     %r2,%r14
+        lg      %r3,168(%r15)
+        larl    %r14,ftrace_dyn_func
+        lg      %r14,0(%r14)
+        basr    %r14,%r14
+        aghi    %r15,160
+        lmg     %r2,%r5,32(%r15)
+        lg      %r14,112(%r15)
         br      %r14
 
-#else /* CONFIG_64BIT */
+        .data
+        .globl  ftrace_dyn_func
+ftrace_dyn_func:
+        .quad   ftrace_stub
+        .previous
+
+#else /* CONFIG_DYNAMIC_FTRACE */
 
-.globl _mcount
+        .globl _mcount
 _mcount:
-        stmg    %r0,%r5,16(%r15)
+        stmg    %r2,%r5,32(%r15)
         stg     %r14,112(%r15)
         lgr     %r1,%r15
         aghi    %r15,-160
@@ -47,12 +57,67 @@ _mcount:
         lg      %r14,0(%r14)
         basr    %r14,%r14
         aghi    %r15,160
-        lmg     %r0,%r5,16(%r15)
+        lmg     %r2,%r5,32(%r15)
         lg      %r14,112(%r15)
         br      %r14
 
-.globl ftrace_stub
-ftrace_stub:
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+#else /* CONFIG_64BIT */
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+        .globl _mcount
+_mcount:
+        br      %r14
+
+        .globl ftrace_caller
+ftrace_caller:
+        stm     %r2,%r5,16(%r15)
+        st      %r14,56(%r15)
+        lr      %r1,%r15
+        ahi     %r15,-96
+        l       %r3,100(%r15)
+        la      %r2,0(%r14)
+        st      %r1,__SF_BACKCHAIN(%r15)
+        la      %r3,0(%r3)
+        bras    %r14,0f
+        .long   ftrace_dyn_func
+0:      l       %r14,0(%r14)
+        l       %r14,0(%r14)
+        basr    %r14,%r14
+        ahi     %r15,96
+        lm      %r2,%r5,16(%r15)
+        l       %r14,56(%r15)
+        br      %r14
+
+        .data
+        .globl  ftrace_dyn_func
+ftrace_dyn_func:
+        .long   ftrace_stub
+        .previous
+
+#else /* CONFIG_DYNAMIC_FTRACE */
+
+        .globl _mcount
+_mcount:
+        stm     %r2,%r5,16(%r15)
+        st      %r14,56(%r15)
+        lr      %r1,%r15
+        ahi     %r15,-96
+        l       %r3,100(%r15)
+        la      %r2,0(%r14)
+        st      %r1,__SF_BACKCHAIN(%r15)
+        la      %r3,0(%r3)
+        bras    %r14,0f
+        .long   ftrace_trace_function
+0:      l       %r14,0(%r14)
+        l       %r14,0(%r14)
+        basr    %r14,%r14
+        ahi     %r15,96
+        lm      %r2,%r5,16(%r15)
+        l       %r14,56(%r15)
         br      %r14
 
+#endif /* CONFIG_DYNAMIC_FTRACE */
 #endif /* CONFIG_64BIT */
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 7402b6a39ead..9717717c6fea 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -42,6 +42,7 @@
 #include <linux/ctype.h>
 #include <linux/reboot.h>
 #include <linux/topology.h>
+#include <linux/ftrace.h>
 
 #include <asm/ipl.h>
 #include <asm/uaccess.h>
@@ -442,6 +443,7 @@ setup_lowcore(void)
         lc->steal_timer = S390_lowcore.steal_timer;
         lc->last_update_timer = S390_lowcore.last_update_timer;
         lc->last_update_clock = S390_lowcore.last_update_clock;
+        lc->ftrace_func = S390_lowcore.ftrace_func;
         set_prefix((u32)(unsigned long) lc);
         lowcore_ptr[0] = lc;
 }
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 0af302ceac2d..cc8c484984e3 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -572,6 +572,7 @@ int __cpuinit __cpu_up(unsigned int cpu)
         cpu_lowcore->cpu_nr = cpu;
         cpu_lowcore->kernel_asce = S390_lowcore.kernel_asce;
         cpu_lowcore->machine_flags = S390_lowcore.machine_flags;
+        cpu_lowcore->ftrace_func = S390_lowcore.ftrace_func;
         eieio();
 
         while (signal_processor(cpu, sigp_restart) == sigp_busy)