powerpc64: port of the function graph tracer

This is a port of the function graph tracer that was written by
Frederic Weisbecker for the x86.

This only works for PPC64 at the moment and only for static tracing.
PPC32 and dynamic function graph tracing support will come later.

The trace produces a visual calling of functions:

 # tracer: function_graph
 #
 # CPU  DURATION                  FUNCTION CALLS
 # |     |   |                     |   |   |   |
  0)   2.224 us    |                        }
  0) ! 271.024 us  |                      }
  0) ! 320.080 us  |                    }
  0) ! 324.656 us  |                  }
  0) ! 329.136 us  |                }
  0)               |                .put_prev_task_fair() {
  0)               |                  .update_curr() {
  0)   2.240 us    |                    .update_min_vruntime();
  0)   6.512 us    |                  }
  0)   2.528 us    |                  .__enqueue_entity();
  0) + 15.536 us   |                }
  0)               |                .pick_next_task_fair() {
  0)   2.032 us    |                  .__pick_next_entity();
  0)   2.064 us    |                  .__clear_buddies();
  0)               |                  .set_next_entity() {
  0)   2.672 us    |                    .__dequeue_entity();
  0)   6.864 us    |                  }

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>

6 files changed, 154 insertions, 10 deletions

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index ccdd8de3c558..e122d241f17d 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -111,6 +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 ARCH_WANT_OPTIONAL_GPIOLIB
         select HAVE_IDE
         select HAVE_IOREMAP_PROT
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index d15992119085..583ba6493a62 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -18,12 +18,10 @@ CFLAGS_REMOVE_cputable.o = -pg -mno-sched-epilog
 CFLAGS_REMOVE_prom_init.o = -pg -mno-sched-epilog
 CFLAGS_REMOVE_btext.o = -pg -mno-sched-epilog
 CFLAGS_REMOVE_prom.o = -pg -mno-sched-epilog
-
-ifdef CONFIG_DYNAMIC_FTRACE
-# dynamic ftrace setup.
+# do not trace tracer code
 CFLAGS_REMOVE_ftrace.o = -pg -mno-sched-epilog
-endif
-
+# timers used by tracing
+CFLAGS_REMOVE_time.o = -pg -mno-sched-epilog
 endif
 
 obj-y                           := cputable.o ptrace.o syscalls.o \
@@ -95,6 +93,7 @@ obj-$(CONFIG_AUDIT)		+= audit.o
 obj64-$(CONFIG_AUDIT)           += compat_audit.o
 
 obj-$(CONFIG_DYNAMIC_FTRACE)    += ftrace.o
+obj-$(CONFIG_FUNCTION_GRAPH_TRACER)     += ftrace.o
 
 obj-$(CONFIG_8XX_MINIMAL_FPEMU) += softemu8xx.o
 
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 383ed6eb0085..a32699e74c3c 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -931,13 +931,65 @@ _GLOBAL(_mcount)
         ld      r5,0(r5)
         mtctr   r5
         bctrl
-
         nop
+
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+        b       ftrace_graph_caller
+#endif
         ld      r0, 128(r1)
         mtlr    r0
         addi    r1, r1, 112
 _GLOBAL(ftrace_stub)
         blr
 
-#endif
-#endif
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ftrace_graph_caller:
+        /* load r4 with local address */
+        ld      r4, 128(r1)
+        subi    r4, r4, MCOUNT_INSN_SIZE
+
+        /* get the parent address */
+        ld      r11, 112(r1)
+        addi    r3, r11, 16
+
+        bl      .prepare_ftrace_return
+        nop
+
+        ld      r0, 128(r1)
+        mtlr    r0
+        addi    r1, r1, 112
+        blr
+
+_GLOBAL(return_to_handler)
+        /* need to save return values */
+        std     r4,  -32(r1)
+        std     r3,  -24(r1)
+        /* save TOC */
+        std     r2,  -16(r1)
+        std     r31, -8(r1)
+        mr      r31, r1
+        stdu    r1, -112(r1)
+
+        /* update the TOC */
+        LOAD_REG_IMMEDIATE(r4,ftrace_return_to_handler)
+        ld      r2, 8(r4)
+
+        bl      .ftrace_return_to_handler
+        nop
+
+        /* return value has real return address */
+        mtlr    r3
+
+        ld      r1, 0(r1)
+        ld      r4,  -32(r1)
+        ld      r3,  -24(r1)
+        ld      r2,  -16(r1)
+        ld      r31, -8(r1)
+
+        /* Jump back to real return address */
+        blr
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+#endif /* CONFIG_FUNCTION_TRACER */
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 4112175183d3..c9b1547f65a5 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -5,6 +5,9 @@
  *
  * Thanks goes out to P.A. Semi, Inc for supplying me with a PPC64 box.
  *
+ * Added function graph tracer code, taken from x86 that was written
+ * by Frederic Weisbecker, and ported to PPC by Steven Rostedt.
+ *
  */
 
 #include <linux/spinlock.h>
@@ -20,8 +23,6 @@
 #include <asm/code-patching.h>
 #include <asm/ftrace.h>
 
-static unsigned int ftrace_nop = PPC_NOP_INSTR;
-
 #ifdef CONFIG_PPC32
 # define GET_ADDR(addr) addr
 #else
@@ -29,6 +30,8 @@ static unsigned int ftrace_nop = PPC_NOP_INSTR;
 # define GET_ADDR(addr) (*(unsigned long *)addr)
 #endif
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+static unsigned int ftrace_nop = PPC_NOP_INSTR;
 
 static unsigned int ftrace_calc_offset(long ip, long addr)
 {
@@ -525,3 +528,75 @@ int __init ftrace_dyn_arch_init(void *data)
 
         return 0;
 }
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+
+/*
+ * Hook the return address and push it in the stack of return addrs
+ * in current thread info.
+ */
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
+{
+        unsigned long old;
+        unsigned long long calltime;
+        int faulted;
+        struct ftrace_graph_ent trace;
+        unsigned long return_hooker = (unsigned long)
+                                &return_to_handler;
+
+        if (unlikely(atomic_read(&current->tracing_graph_pause)))
+                return;
+
+        return_hooker = GET_ADDR(return_hooker);
+
+        /*
+         * Protect against fault, even if it shouldn't
+         * happen. This tool is too much intrusive to
+         * ignore such a protection.
+         */
+        asm volatile(
+                "1: " PPC_LL "%[old], 0(%[parent])\n"
+                "2: " PPC_STL "%[return_hooker], 0(%[parent])\n"
+                "   li %[faulted], 0\n"
+                "3:"
+
+                ".section .fixup, \"ax\"\n"
+                "4: li %[faulted], 1\n"
+                "   b 3b\n"
+                ".previous\n"
+
+                ".section __ex_table,\"a\"\n"
+                        PPC_LONG_ALIGN "\n"
+                        PPC_LONG "1b,4b\n"
+                        PPC_LONG "2b,4b\n"
+                ".previous"
+
+                : [old] "=r" (old), [faulted] "=r" (faulted)
+                : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
+                : "memory"
+        );
+
+        if (unlikely(faulted)) {
+                ftrace_graph_stop();
+                WARN_ON(1);
+                return;
+        }
+
+        calltime = cpu_clock(raw_smp_processor_id());
+
+        if (ftrace_push_return_trace(old, calltime,
+                                self_addr, &trace.depth) == -EBUSY) {
+                *parent = old;
+                return;
+        }
+
+        trace.func = self_addr;
+
+        /* Only trace if the calling function expects to */
+        if (!ftrace_graph_entry(&trace)) {
+                current->curr_ret_stack--;
+                *parent = old;
+        }
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index fb7049c054c0..8ede428e76c0 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -33,6 +33,7 @@
 #include <linux/mqueue.h>
 #include <linux/hardirq.h>
 #include <linux/utsname.h>
+#include <linux/ftrace.h>
 #include <linux/kernel_stat.h>
 
 #include <asm/pgtable.h>
@@ -1008,6 +1009,14 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
         unsigned long sp, ip, lr, newsp;
         int count = 0;
         int firstframe = 1;
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+        int curr_frame = current->curr_ret_stack;
+        extern void return_to_handler(void);
+        unsigned long addr = (unsigned long)return_to_handler;
+#ifdef CONFIG_PPC64
+        addr = *(unsigned long*)addr;
+#endif
+#endif
 
         sp = (unsigned long) stack;
         if (tsk == NULL)
@@ -1030,6 +1039,13 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
                 ip = stack[STACK_FRAME_LR_SAVE];
                 if (!firstframe || ip != lr) {
                         printk("["REG"] ["REG"] %pS", sp, ip, (void *)ip);
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+                        if (ip == addr && curr_frame >= 0) {
+                                printk(" (%pS)",
+                                       (void *)current->ret_stack[curr_frame].ret);
+                                curr_frame--;
+                        }
+#endif
                         if (firstframe)
                                 printk(" (unreliable)");
                         printk("\n");
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 161b9b9691f0..895af44bf1f4 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -58,6 +58,7 @@ SECTIONS
                 SCHED_TEXT
                 LOCK_TEXT
                 KPROBES_TEXT
+                IRQENTRY_TEXT
 
 #ifdef CONFIG_PPC32
                 *(.got1)