powerpc64, tracing: add function graph tracer with dynamic tracing

This is the port of the function graph tracer to PowerPC with
dynamic tracing.

Geoff Lavand tested on PS3.

Tested-by: Geoff Levand <geoffrey.levand@am.sony.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

3 files changed, 49 insertions, 8 deletions

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index e122d241f17d..b298fb0703de 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -111,7 +111,7 @@ config PPC
         select HAVE_FTRACE_MCOUNT_RECORD
         select HAVE_DYNAMIC_FTRACE
         select HAVE_FUNCTION_TRACER
-        select HAVE_FUNCTION_GRAPH_TRACER if !DYNAMIC_FTRACE && PPC64
+        select HAVE_FUNCTION_GRAPH_TRACER if PPC64
         select ARCH_WANT_OPTIONAL_GPIOLIB
         select HAVE_IDE
         select HAVE_IOREMAP_PROT
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index a32699e74c3c..9f61fd61f277 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -908,6 +908,12 @@ _GLOBAL(ftrace_caller)
 ftrace_call:
         bl      ftrace_stub
         nop
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+.globl ftrace_graph_call
+ftrace_graph_call:
+        b       ftrace_graph_stub
+_GLOBAL(ftrace_graph_stub)
+#endif
         ld      r0, 128(r1)
         mtlr    r0
         addi    r1, r1, 112
@@ -946,7 +952,7 @@ _GLOBAL(ftrace_stub)
 #endif /* CONFIG_DYNAMIC_FTRACE */
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
-ftrace_graph_caller:
+_GLOBAL(ftrace_graph_caller)
         /* load r4 with local address */
         ld      r4, 128(r1)
         subi    r4, r4, MCOUNT_INSN_SIZE
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index c9b1547f65a5..7538b944fa52 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -43,7 +43,8 @@ static unsigned char *ftrace_nop_replace(void)
         return (char *)&ftrace_nop;
 }
 
-static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
+static unsigned char *
+ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
 {
         static unsigned int op;
 
@@ -55,8 +56,9 @@ static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
          */
         addr = GET_ADDR(addr);
 
-        /* Set to "bl addr" */
-        op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);
+        /* if (link) set op to 'bl' else 'b' */
+        op = 0x48000000 | (link ? 1 : 0);
+        op |= (ftrace_calc_offset(ip, addr) & 0x03fffffc);
 
         /*
          * No locking needed, this must be called via kstop_machine
@@ -344,7 +346,7 @@ int ftrace_make_nop(struct module *mod,
          */
         if (test_24bit_addr(ip, addr)) {
                 /* within range */
-                old = ftrace_call_replace(ip, addr);
+                old = ftrace_call_replace(ip, addr, 1);
                 new = ftrace_nop_replace();
                 return ftrace_modify_code(ip, old, new);
         }
@@ -484,7 +486,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
         if (test_24bit_addr(ip, addr)) {
                 /* within range */
                 old = ftrace_nop_replace();
-                new = ftrace_call_replace(ip, addr);
+                new = ftrace_call_replace(ip, addr, 1);
                 return ftrace_modify_code(ip, old, new);
         }
 
@@ -513,7 +515,7 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
         int ret;
 
         memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
-        new = ftrace_call_replace(ip, (unsigned long)func);
+        new = ftrace_call_replace(ip, (unsigned long)func, 1);
         ret = ftrace_modify_code(ip, old, new);
 
         return ret;
@@ -532,6 +534,39 @@ int __init ftrace_dyn_arch_init(void *data)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+extern void ftrace_graph_call(void);
+extern void ftrace_graph_stub(void);
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+        unsigned long ip = (unsigned long)(&ftrace_graph_call);
+        unsigned long addr = (unsigned long)(&ftrace_graph_caller);
+        unsigned long stub = (unsigned long)(&ftrace_graph_stub);
+        unsigned char old[MCOUNT_INSN_SIZE], *new;
+
+        new = ftrace_call_replace(ip, stub, 0);
+        memcpy(old, new, MCOUNT_INSN_SIZE);
+        new = ftrace_call_replace(ip, addr, 0);
+
+        return ftrace_modify_code(ip, old, new);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+        unsigned long ip = (unsigned long)(&ftrace_graph_call);
+        unsigned long addr = (unsigned long)(&ftrace_graph_caller);
+        unsigned long stub = (unsigned long)(&ftrace_graph_stub);
+        unsigned char old[MCOUNT_INSN_SIZE], *new;
+
+        new = ftrace_call_replace(ip, addr, 0);
+        memcpy(old, new, MCOUNT_INSN_SIZE);
+        new = ftrace_call_replace(ip, stub, 0);
+
+        return ftrace_modify_code(ip, old, new);
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
 /*
  * Hook the return address and push it in the stack of return addrs
  * in current thread info.