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Subject[RFC PATCH 01/22 -v2] Add basic support for gcc profiler instrumentation
If CONFIG_MCOUNT is selected and /proc/sys/kernel/mcount_enabled is set to a
non-zero value the mcount routine will be called everytime we enter a kernel
function that is not marked with the "notrace" attribute.

The mcount routine will then call a registered function if a function
happens to be registered.

[This code has been highly hacked by Steven Rostedt, so don't
blame Arnaldo for all of this ;-) ]

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
Makefile | 4 ++
arch/x86/Kconfig | 4 ++
arch/x86/kernel/Makefile_32 | 1
arch/x86/kernel/entry_64.S | 40 ++++++++++++++++++++
arch/x86/kernel/mcount-wrapper.S | 25 ++++++++++++
include/linux/linkage.h | 2 +
include/linux/mcount.h | 21 ++++++++++
kernel/sysctl.c | 11 +++++
lib/Kconfig.debug | 2 +
lib/Makefile | 2 +
lib/tracing/Kconfig | 7 +++
lib/tracing/Makefile | 3 +
lib/tracing/mcount.c | 77 +++++++++++++++++++++++++++++++++++++++
13 files changed, 199 insertions(+)
create mode 100644 arch/i386/kernel/mcount-wrapper.S
create mode 100644 lib/tracing/Kconfig
create mode 100644 lib/tracing/Makefile
create mode 100644 lib/tracing/mcount.c
create mode 100644 lib/tracing/mcount.h
Index: linux-compile-i386.git/Makefile
===================================================================
--- linux-compile-i386.git.orig/Makefile 2008-01-09 14:09:36.000000000 -0500
+++ linux-compile-i386.git/Makefile 2008-01-09 14:10:07.000000000 -0500
@@ -509,6 +509,10 @@ endif

include $(srctree)/arch/$(SRCARCH)/Makefile

+# MCOUNT expects frame pointer
+ifdef CONFIG_MCOUNT
+KBUILD_CFLAGS += -pg
+endif
ifdef CONFIG_FRAME_POINTER
KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls
else
Index: linux-compile-i386.git/arch/x86/Kconfig
===================================================================
--- linux-compile-i386.git.orig/arch/x86/Kconfig 2008-01-09 14:09:36.000000000 -0500
+++ linux-compile-i386.git/arch/x86/Kconfig 2008-01-09 14:10:07.000000000 -0500
@@ -28,6 +28,10 @@ config GENERIC_CMOS_UPDATE
bool
default y

+config ARCH_HAS_MCOUNT
+ bool
+ default y
+
config CLOCKSOURCE_WATCHDOG
bool
default y
Index: linux-compile-i386.git/arch/x86/kernel/Makefile_32
===================================================================
--- linux-compile-i386.git.orig/arch/x86/kernel/Makefile_32 2008-01-09 14:09:36.000000000 -0500
+++ linux-compile-i386.git/arch/x86/kernel/Makefile_32 2008-01-09 14:10:07.000000000 -0500
@@ -23,6 +23,7 @@ obj-$(CONFIG_APM) += apm_32.o
obj-$(CONFIG_X86_SMP) += smp_32.o smpboot_32.o tsc_sync.o
obj-$(CONFIG_SMP) += smpcommon_32.o
obj-$(CONFIG_X86_TRAMPOLINE) += trampoline_32.o
+obj-$(CONFIG_MCOUNT) += mcount-wrapper.o
obj-$(CONFIG_X86_MPPARSE) += mpparse_32.o
obj-$(CONFIG_X86_LOCAL_APIC) += apic_32.o nmi_32.o
obj-$(CONFIG_X86_IO_APIC) += io_apic_32.o
Index: linux-compile-i386.git/arch/x86/kernel/mcount-wrapper.S
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-compile-i386.git/arch/x86/kernel/mcount-wrapper.S 2008-01-09 14:10:07.000000000 -0500
@@ -0,0 +1,25 @@
+/*
+ * linux/arch/x86/mcount-wrapper.S
+ *
+ * Copyright (C) 2004 Ingo Molnar
+ */
+
+.globl mcount
+mcount:
+ cmpl $0, mcount_enabled
+ jz out
+
+ push %ebp
+ mov %esp, %ebp
+ pushl %eax
+ pushl %ecx
+ pushl %edx
+
+ call __mcount
+
+ popl %edx
+ popl %ecx
+ popl %eax
+ popl %ebp
+out:
+ ret
Index: linux-compile-i386.git/include/linux/linkage.h
===================================================================
--- linux-compile-i386.git.orig/include/linux/linkage.h 2008-01-09 14:09:36.000000000 -0500
+++ linux-compile-i386.git/include/linux/linkage.h 2008-01-09 14:10:07.000000000 -0500
@@ -3,6 +3,8 @@

#include <asm/linkage.h>

+#define notrace __attribute__((no_instrument_function))
+
#ifdef __cplusplus
#define CPP_ASMLINKAGE extern "C"
#else
Index: linux-compile-i386.git/kernel/sysctl.c
===================================================================
--- linux-compile-i386.git.orig/kernel/sysctl.c 2008-01-09 14:09:36.000000000 -0500
+++ linux-compile-i386.git/kernel/sysctl.c 2008-01-09 14:10:07.000000000 -0500
@@ -46,6 +46,7 @@
#include <linux/nfs_fs.h>
#include <linux/acpi.h>
#include <linux/reboot.h>
+#include <linux/mcount.h>

#include <asm/uaccess.h>
#include <asm/processor.h>
@@ -470,6 +471,16 @@ static struct ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = &proc_dointvec,
},
+#ifdef CONFIG_MCOUNT
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "mcount_enabled",
+ .data = &mcount_enabled,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
+#endif
#ifdef CONFIG_KMOD
{
.ctl_name = KERN_MODPROBE,
Index: linux-compile-i386.git/lib/Kconfig.debug
===================================================================
--- linux-compile-i386.git.orig/lib/Kconfig.debug 2008-01-09 14:09:36.000000000 -0500
+++ linux-compile-i386.git/lib/Kconfig.debug 2008-01-09 14:10:07.000000000 -0500
@@ -517,4 +517,6 @@ config FAULT_INJECTION_STACKTRACE_FILTER
help
Provide stacktrace filter for fault-injection capabilities

+source lib/tracing/Kconfig
+
source "samples/Kconfig"
Index: linux-compile-i386.git/lib/Makefile
===================================================================
--- linux-compile-i386.git.orig/lib/Makefile 2008-01-09 14:09:36.000000000 -0500
+++ linux-compile-i386.git/lib/Makefile 2008-01-09 14:10:07.000000000 -0500
@@ -66,6 +66,8 @@ obj-$(CONFIG_AUDIT_GENERIC) += audit.o
obj-$(CONFIG_SWIOTLB) += swiotlb.o
obj-$(CONFIG_FAULT_INJECTION) += fault-inject.o

+obj-$(CONFIG_MCOUNT) += tracing/
+
lib-$(CONFIG_GENERIC_BUG) += bug.o

hostprogs-y := gen_crc32table
Index: linux-compile-i386.git/lib/tracing/Kconfig
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-compile-i386.git/lib/tracing/Kconfig 2008-01-09 15:17:48.000000000 -0500
@@ -0,0 +1,7 @@
+
+# MCOUNT itself is useless, or will just be added overhead.
+# It needs something to register a function with it.
+config MCOUNT
+ bool
+ depends on DEBUG_KERNEL
+ select FRAME_POINTER
Index: linux-compile-i386.git/lib/tracing/Makefile
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-compile-i386.git/lib/tracing/Makefile 2008-01-09 15:17:48.000000000 -0500
@@ -0,0 +1,3 @@
+obj-$(CONFIG_MCOUNT) += libmcount.o
+
+libmcount-y := mcount.o
Index: linux-compile-i386.git/lib/tracing/mcount.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-compile-i386.git/lib/tracing/mcount.c 2008-01-09 14:10:07.000000000 -0500
@@ -0,0 +1,77 @@
+/*
+ * Infrastructure for profiling code inserted by 'gcc -pg'.
+ *
+ * Copyright (C) 2007 Arnaldo Carvalho de Melo <acme@redhat.com>
+ *
+ * Converted to be more generic:
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ *
+ * From code in the latency_tracer, that is:
+ *
+ * Copyright (C) 2004-2006 Ingo Molnar
+ * Copyright (C) 2004 William Lee Irwin III
+ */
+
+#include <linux/module.h>
+#include <linux/mcount.h>
+
+/*
+ * Since we have nothing protecting between the test of
+ * mcount_trace_function and the call to it, we can't
+ * set it to NULL without risking a race that will have
+ * the kernel call the NULL pointer. Instead, we just
+ * set the function pointer to a dummy function.
+ */
+notrace void dummy_mcount_tracer(unsigned long ip,
+ unsigned long parent_ip)
+{
+ /* do nothing */
+}
+
+mcount_func_t mcount_trace_function __read_mostly = dummy_mcount_tracer;
+int mcount_enabled __read_mostly;
+
+/** __mcount - hook for profiling
+ *
+ * This routine is called from the arch specific mcount routine, that in turn is
+ * called from code inserted by gcc -pg.
+ */
+notrace void __mcount(void)
+{
+ mcount_trace_function(CALLER_ADDR1, CALLER_ADDR2);
+}
+EXPORT_SYMBOL_GPL(mcount);
+/*
+ * The above EXPORT_SYMBOL is for the gcc call of mcount and not the
+ * function __mcount that it is underneath. I put the export there
+ * to fool checkpatch.pl. It wants that export to be with the
+ * function, but that function happens to be in assembly.
+ */
+
+/**
+ * register_mcount_function - register a function for profiling
+ * @func - the function for profiling.
+ *
+ * Register a function to be called by all functions in the
+ * kernel.
+ *
+ * Note: @func and all the functions it calls must be labeled
+ * with "notrace", otherwise it will go into a
+ * recursive loop.
+ */
+int register_mcount_function(mcount_func_t func)
+{
+ mcount_trace_function = func;
+ return 0;
+}
+
+/**
+ * clear_mcount_function - reset the mcount function
+ *
+ * This NULLs the mcount function and in essence stops
+ * tracing. There may be lag
+ */
+void clear_mcount_function(void)
+{
+ mcount_trace_function = dummy_mcount_tracer;
+}
Index: linux-compile-i386.git/include/linux/mcount.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-compile-i386.git/include/linux/mcount.h 2008-01-09 15:17:20.000000000 -0500
@@ -0,0 +1,21 @@
+#ifndef _LINUX_MCOUNT_H
+#define _LINUX_MCOUNT_H
+
+#ifdef CONFIG_MCOUNT
+extern int mcount_enabled;
+
+#include <linux/linkage.h>
+
+#define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
+#define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
+#define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
+
+typedef void (*mcount_func_t)(unsigned long ip, unsigned long parent_ip);
+
+extern void mcount(void);
+
+int register_mcount_function(mcount_func_t func);
+void clear_mcount_function(void);
+
+#endif /* CONFIG_MCOUNT */
+#endif /* _LINUX_MCOUNT_H */
Index: linux-compile-i386.git/arch/x86/kernel/entry_64.S
===================================================================
--- linux-compile-i386.git.orig/arch/x86/kernel/entry_64.S 2008-01-09 14:09:36.000000000 -0500
+++ linux-compile-i386.git/arch/x86/kernel/entry_64.S 2008-01-09 14:10:07.000000000 -0500
@@ -53,6 +53,46 @@

.code64

+#ifdef CONFIG_MCOUNT
+
+ENTRY(mcount)
+ cmpl $0, mcount_enabled
+ jz out
+
+ push %rbp
+ mov %rsp,%rbp
+
+ push %r11
+ push %r10
+ push %r9
+ push %r8
+ push %rdi
+ push %rsi
+ push %rdx
+ push %rcx
+ push %rax
+
+ mov 0x0(%rbp),%rax
+ mov 0x8(%rbp),%rdi
+ mov 0x8(%rax),%rsi
+
+ call *mcount_trace_function
+
+ pop %rax
+ pop %rcx
+ pop %rdx
+ pop %rsi
+ pop %rdi
+ pop %r8
+ pop %r9
+ pop %r10
+ pop %r11
+
+ pop %rbp
+out:
+ ret
+#endif
+
#ifndef CONFIG_PREEMPT
#define retint_kernel retint_restore_args
#endif
--


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