Blackfin: initial support for ftrace grapher

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

4 files changed, 114 insertions, 0 deletions

diff --git a/arch/blackfin/kernel/Makefile b/arch/blackfin/kernel/Makefile
index d2ae285e5b6e..3731088e181b 100644
--- a/arch/blackfin/kernel/Makefile
+++ b/arch/blackfin/kernel/Makefile
@@ -16,6 +16,9 @@ else
 endif
 
 obj-$(CONFIG_FUNCTION_TRACER)        += ftrace-entry.o
+obj-$(CONFIG_FUNCTION_GRAPH_TRACER)  += ftrace.o
+CFLAGS_REMOVE_ftrace.o = -pg
+
 obj-$(CONFIG_IPIPE)                  += ipipe.o
 obj-$(CONFIG_IPIPE_TRACE_MCOUNT)     += mcount.o
 obj-$(CONFIG_BFIN_GPTIMERS)          += gptimers.o
diff --git a/arch/blackfin/kernel/ftrace-entry.S b/arch/blackfin/kernel/ftrace-entry.S
index ce71487b515f..6980b7a0615d 100644
--- a/arch/blackfin/kernel/ftrace-entry.S
+++ b/arch/blackfin/kernel/ftrace-entry.S
@@ -35,6 +35,28 @@ ENTRY(__mcount)
         cc = r2 == r3;
         if ! cc jump .Ldo_trace;
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+        /* if the ftrace_graph_return function pointer is not set to
+         * the ftrace_stub entry, call prepare_ftrace_return().
+         */
+        p0.l = _ftrace_graph_return;
+        p0.h = _ftrace_graph_return;
+        r3 = [p0];
+        cc = r2 == r3;
+        if ! cc jump _ftrace_graph_caller;
+
+        /* similarly, if the ftrace_graph_entry function pointer is not
+         * set to the ftrace_graph_entry_stub entry, ...
+         */
+        p0.l = _ftrace_graph_entry;
+        p0.h = _ftrace_graph_entry;
+        r2.l = _ftrace_graph_entry_stub;
+        r2.h = _ftrace_graph_entry_stub;
+        r3 = [p0];
+        cc = r2 == r3;
+        if ! cc jump _ftrace_graph_caller;
+#endif
+
         r2 = [sp++];
         rts;
 
@@ -61,6 +83,7 @@ ENTRY(__mcount)
         call (p0);
 
         /* restore state and get out of dodge */
+.Lfinish_trace:
         rets = [sp++];
         r1 = [sp++];
         r0 = [sp++];
@@ -70,3 +93,48 @@ ENTRY(__mcount)
 _ftrace_stub:
         rts;
 ENDPROC(__mcount)
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+/* The prepare_ftrace_return() function is similar to the trace function
+ * except it takes a pointer to the location of the frompc.  This is so
+ * the prepare_ftrace_return() can hijack it temporarily for probing
+ * purposes.
+ */
+ENTRY(_ftrace_graph_caller)
+        /* save first/second function arg and the return register */
+        [--sp] = r0;
+        [--sp] = r1;
+        [--sp] = rets;
+
+        r0 = fp;
+        r1 = rets;
+        r0 += 4;
+        r1 += -MCOUNT_INSN_SIZE;
+        call _prepare_ftrace_return;
+
+        jump .Lfinish_trace;
+ENDPROC(_ftrace_graph_caller)
+
+/* Undo the rewrite caused by ftrace_graph_caller().  The common function
+ * ftrace_return_to_handler() will return the original rets so we can
+ * restore it and be on our way.
+ */
+ENTRY(_return_to_handler)
+        /* make sure original return values are saved */
+        [--sp] = p0;
+        [--sp] = r0;
+        [--sp] = r1;
+
+        /* get original return address */
+        call _ftrace_return_to_handler;
+        rets = r0;
+
+        /* anomaly 05000371 - make sure we have at least three instructions
+         * between rets setting and the return
+         */
+        r1 = [sp++];
+        r0 = [sp++];
+        p0 = [sp++];
+        rts;
+ENDPROC(_return_to_handler)
+#endif
diff --git a/arch/blackfin/kernel/ftrace.c b/arch/blackfin/kernel/ftrace.c
new file mode 100644
index 000000000000..905bfc40a00b
--- /dev/null
+++ b/arch/blackfin/kernel/ftrace.c
@@ -0,0 +1,42 @@
+/*
+ * ftrace graph code
+ *
+ * Copyright (C) 2009 Analog Devices Inc.
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <linux/ftrace.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <asm/atomic.h>
+
+#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)
+{
+        struct ftrace_graph_ent trace;
+        unsigned long return_hooker = (unsigned long)&return_to_handler;
+
+        if (unlikely(atomic_read(&current->tracing_graph_pause)))
+                return;
+
+        if (ftrace_push_return_trace(*parent, self_addr, &trace.depth) == -EBUSY)
+                return;
+
+        trace.func = self_addr;
+
+        /* Only trace if the calling function expects to */
+        if (!ftrace_graph_entry(&trace)) {
+                current->curr_ret_stack--;
+                return;
+        }
+
+        /* all is well in the world !  hijack RETS ... */
+        *parent = return_hooker;
+}
+
+#endif
diff --git a/arch/blackfin/kernel/vmlinux.lds.S b/arch/blackfin/kernel/vmlinux.lds.S
index 119fbdb46475..6ac307ca0d80 100644
--- a/arch/blackfin/kernel/vmlinux.lds.S
+++ b/arch/blackfin/kernel/vmlinux.lds.S
@@ -54,6 +54,7 @@ SECTIONS
                 SCHED_TEXT
 #endif
                 LOCK_TEXT
+                IRQENTRY_TEXT
                 KPROBES_TEXT
                 *(.text.*)
                 *(.fixup)