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Date: Fri, 5 Mar 2010 16:31:26 -0800
From: Tim Bird <tim.bird@...sony.com>
To: Tony Lindgren <tony@...mide.com>,
Russell King <rmk@....linux.org.uk>,
linux-arm-kernel <linux-arm-kernel@...ts.arm.linux.org.uk>,
linux kernel <linux-kernel@...r.kernel.org>,
Steven Rostedt <rostedt@...dmis.org>,
Frederic Weisbecker <fweisbec@...il.com>
Subject: [PATCH 2/2] ftrace - add ftrace function_graph support on ARM
Add ftrace function-graph tracer support for ARM.
This includes adding code in mcount to check for
(and call) a registered function graph trace entry
routine, and adding code to support a return
trampoline, to catch the function exit.
IRQENTRY_TEXT was added to vmlinux.lds.S (to eliminate
a compiler error on kernel/trace/trace_functions_graph.c),
although no routines were marked as __irq_entry.
Signed-off-by: Tim Bird <tim.bird@...sony.com>
---
arch/arm/Kconfig | 1
arch/arm/kernel/Makefile | 4 +--
arch/arm/kernel/entry-common.S | 36 +++++++++++++++++++++++++++++++-
arch/arm/kernel/ftrace_graph.c | 46 +++++++++++++++++++++++++++++++++++++++++
arch/arm/kernel/vmlinux.lds.S | 1
5 files changed, 85 insertions(+), 3 deletions(-)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -18,6 +18,7 @@ config ARM
select HAVE_KPROBES if (!XIP_KERNEL)
select HAVE_KRETPROBES if (HAVE_KPROBES)
select HAVE_FUNCTION_TRACER if (!XIP_KERNEL)
+ select HAVE_FUNCTION_GRAPH_TRACER if (!XIP_KERNEL)
select HAVE_GENERIC_DMA_COHERENT
select HAVE_KERNEL_GZIP
select HAVE_KERNEL_LZO
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -5,9 +5,8 @@
CPPFLAGS_vmlinux.lds := -DTEXT_OFFSET=$(TEXT_OFFSET)
AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
-ifdef CONFIG_DYNAMIC_FTRACE
CFLAGS_REMOVE_ftrace.o = -pg
-endif
+CFLAGS_REMOVE_ftrace_graph.o = -pg
CFLAGS_REMOVE_return_address.o = -pg
@@ -31,6 +30,7 @@ obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_HAVE_ARM_SCU) += smp_scu.o
obj-$(CONFIG_HAVE_ARM_TWD) += smp_twd.o
obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
+obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace_graph.o
obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
obj-$(CONFIG_KPROBES) += kprobes.o kprobes-decode.o
obj-$(CONFIG_ATAGS_PROC) += atags.o
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -98,6 +98,11 @@ ENTRY(mcount)
mov r0, lr
sub r0, r0, #MCOUNT_INSN_SIZE
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ @ FIXTHIS - DYNAMIC_FTRACE does not support function graph tracing
+ @ when the dynamic work is revived, this should be supported as well
+#endif
+
.globl mcount_call
mcount_call:
bl ftrace_stub
@@ -144,8 +149,16 @@ ENTRY(mcount)
adr r0, ftrace_stub
cmp r0, r2
bne trace
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ ldr r1, =ftrace_graph_return
+ ldr r2, [r1]
+ cmp r0, r2 @ if *ftrace_graph_return != ftrace_stub
+ bne ftrace_graph_caller
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
ldr lr, [fp, #-4] @ restore lr
- ldmia sp!, {r0-r3, pc}
+ ldmia sp!, {r0-r3, pc} @ return doing nothing
trace:
ldr r1, [fp, #-4] @ lr of instrumented routine
@@ -156,6 +169,27 @@ trace:
ldr lr, [fp, #-4] @ restore lr
ldmia sp!, {r0-r3, pc}
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ENTRY(ftrace_graph_caller)
+ sub r0, fp, #4 @ &lr of instrumented routine (&parent)
+ mov r1, lr @ instrumented routine (func)
+ sub r1, r1, #MCOUNT_INSN_SIZE
+ mov r2, fp @ frame pointer
+ bl prepare_ftrace_return
+ ldr lr, [fp, #-4] @ restore lr
+ ldmia sp!, {r0-r3, pc}
+
+ .globl return_to_handler
+return_to_handler:
+ stmdb sp!, {r0-r3}
+ mov r0, fp @ frame pointer
+ bl ftrace_return_to_handler
+ mov lr, r0 @ r0 has real ret addr
+ ldmia sp!, {r0-r3}
+ mov pc, lr
+
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
#endif /* CONFIG_DYNAMIC_FTRACE */
.globl ftrace_stub
--- /dev/null
+++ b/arch/arm/kernel/ftrace_graph.c
@@ -0,0 +1,46 @@
+/*
+ * function graph tracing support.
+ *
+ * Copyright (C) 2009 Tim Bird <tim.bird@...sony.com>
+ *
+ * For licencing details, see COPYING.
+ *
+ * Defines routine needed for ARM return trampoline for tracing
+ * function exits.
+ */
+
+#include <linux/ftrace.h>
+
+/*
+ * 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 frame_pointer)
+{
+ unsigned long old;
+
+ struct ftrace_graph_ent trace;
+ unsigned long return_hooker = (unsigned long)
+ &return_to_handler;
+
+ if (unlikely(atomic_read(¤t->tracing_graph_pause)))
+ return;
+
+ old = *parent;
+ *parent = return_hooker;
+
+ if (ftrace_push_return_trace(old, self_addr, &trace.depth,
+ frame_pointer) == -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;
+ }
+}
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -91,6 +91,7 @@ SECTIONS
SCHED_TEXT
LOCK_TEXT
KPROBES_TEXT
+ IRQENTRY_TEXT
#ifdef CONFIG_MMU
*(.fixup)
#endif
--
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