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Message-ID: <49FB79CF.3020101@am.sony.com>
Date: Fri, 1 May 2009 15:38:07 -0700
From: Tim Bird <tim.bird@...sony.com>
To: linux kernel <linux-kernel@...r.kernel.org>,
linux-arm-kernel <linux-arm-kernel@...ts.arm.linux.org.uk>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...e.hu>,
Frederic Weisbecker <fweisbec@...il.com>,
Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>,
Russell King <rmk@....linux.org.uk>
Subject: [PATCH 2/2] ftrace: add function-graph tracer support for ARM v2
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 infrastructure to support a return
trampoline to the threadinfo structure.
The code in arch/arm/kernel/ftrace_return.c was
cloned from arch/x86/kernel/ftrace.c
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.
This works for me with a gcc 4.1.1 compiler on an
OMAP OSK board. This is against -tip (or at least,
-tip a few weeks ago - 2.6.30-rc3)
This (v2) patch addresses previously received feedback,
except for one issue. In this version of the code,
a function_graph tracer overrides regular function
tracers. I'll try to address that in a subsequent
patch, but I didn't want to go too long without posting
something.
Note: this code is much cleaner now that much of the
common return-handling code was moved into
kernel/trace_functions_graph.c
Signed-off-by: Tim Bird <tim.bird@...sony.com>
---
arch/arm/Kconfig | 1
arch/arm/kernel/Makefile | 4 +--
arch/arm/kernel/entry-common.S | 34 ++++++++++++++++++++++++++++++
arch/arm/kernel/ftrace_return.c | 44 ++++++++++++++++++++++++++++++++++++++++
arch/arm/kernel/vmlinux.lds.S | 1
5 files changed, 81 insertions(+), 3 deletions(-)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -17,6 +17,7 @@ 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
help
The ARM series is a line of low-power-consumption RISC chip designs
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -4,9 +4,8 @@
AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
-ifdef CONFIG_DYNAMIC_FTRACE
CFLAGS_REMOVE_ftrace.o = -pg
-endif
+CFLAGS_REMOVE_ftrace_return.o = -pg
# Object file lists.
@@ -23,6 +22,7 @@ obj-$(CONFIG_ISA_DMA) += dma-isa.o
obj-$(CONFIG_PCI) += bios32.o isa.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
+obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace_return.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
@@ -112,6 +112,11 @@ 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
@@ -139,8 +144,16 @@ 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
@@ -151,6 +164,25 @@ trace:
mov lr, r1 @ 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
+ 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}
+ 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_return.c
@@ -0,0 +1,44 @@
+/*
+ * function return 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 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) == -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
@@ -99,6 +99,7 @@ SECTIONS
SCHED_TEXT
LOCK_TEXT
KPROBES_TEXT
+ IRQENTRY_TEXT
#ifdef CONFIG_MMU
*(.fixup)
#endif
--
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