linux-kernel - [RFC PATCH v3 06/26] ftrace: sort ftrace entries earlier.

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Date:	Fri, 13 Feb 2015 13:40:31 +0800
From:	Wang Nan <wangnan0@...wei.com>
To:	<linux@....linux.org.uk>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<hpa@...or.com>, <rostedt@...dmis.org>, <ananth@...ibm.com>,
	<anil.s.keshavamurthy@...el.com>, <davem@...emloft.net>,
	<masami.hiramatsu.pt@...achi.com>, <luto@...capital.net>,
	<keescook@...omium.org>, <oleg@...hat.com>, <wangnan0@...wei.com>,
	<dave.long@...aro.org>, <tixy@...aro.org>, <nico@...aro.org>,
	<yalin.wang2010@...il.com>, <catalin.marinas@....com>,
	<Yalin.Wang@...ymobile.com>, <mark.rutland@....com>,
	<dave.hansen@...ux.intel.com>, <jkenisto@...ibm.com>,
	<anton@...ba.org>, <stefani@...bold.net>, <JBeulich@...e.com>,
	<akpm@...ux-foundation.org>, <rusty@...tcorp.com.au>,
	<peterz@...radead.org>, <prarit@...hat.com>, <fabf@...net.be>,
	<hannes@...xchg.org>
CC:	<x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <lizefan@...wei.com>
Subject: [RFC PATCH v3 06/26] ftrace: sort ftrace entries earlier.

By extracting mcount sorting code and sort them earliler, futher patches
will be able to determine whether an address is on an ftrace entry or
not using bsearch().

ftrace_sort_mcount_area() will be called before, during and after
ftrace_init (when module insertion). Ensure it sort kernel mcount table
only once.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
---
 include/linux/ftrace.h |  2 ++
 init/main.c            |  1 +
 kernel/trace/ftrace.c  | 38 ++++++++++++++++++++++++++++++++++++--
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 1da6029..8db315a 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -701,8 +701,10 @@ static inline void __ftrace_enabled_restore(int enabled)
 
 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
 extern void ftrace_init(void);
+extern void ftrace_init_early(void);
 #else
 static inline void ftrace_init(void) { }
+static inline void ftrace_init_early(void) { }
 #endif
 
 /*
diff --git a/init/main.c b/init/main.c
index 6f0f1c5f..eaafc3e 100644
--- a/init/main.c
+++ b/init/main.c
@@ -517,6 +517,7 @@ asmlinkage __visible void __init start_kernel(void)
 	boot_cpu_init();
 	page_address_init();
 	pr_notice("%s", linux_banner);
+	ftrace_init_early();
 	setup_arch(&command_line);
 	mm_init_cpumask(&init_mm);
 	setup_command_line(command_line);
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 6c6cbb1..a75cfbe 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1169,6 +1169,7 @@ struct ftrace_page {
 
 static struct ftrace_page	*ftrace_pages_start;
 static struct ftrace_page	*ftrace_pages;
+static bool kernel_mcount_sorted = false;
 
 static bool __always_inline ftrace_hash_empty(struct ftrace_hash *hash)
 {
@@ -4743,6 +4744,32 @@ static void ftrace_swap_ips(void *a, void *b, int size)
 	*ipb = t;
 }
 
+static void ftrace_sort_mcount_area(unsigned long *start, unsigned long *end)
+{
+	extern unsigned long __start_mcount_loc[];
+	extern unsigned long __stop_mcount_loc[];
+
+	unsigned long count;
+	bool is_kernel_mcount;
+
+	count = end - start;
+	if (!count)
+		return;
+
+	is_kernel_mcount =
+		(start == __start_mcount_loc) &&
+		(end == __stop_mcount_loc);
+
+	if (is_kernel_mcount && kernel_mcount_sorted)
+		return;
+
+	sort(start, count, sizeof(*start),
+		ftrace_cmp_ips, ftrace_swap_ips);
+
+	if (is_kernel_mcount)
+		kernel_mcount_sorted = true;
+}
+
 static int ftrace_process_locs(struct module *mod,
 			       unsigned long *start,
 			       unsigned long *end)
@@ -4761,8 +4788,7 @@ static int ftrace_process_locs(struct module *mod,
 	if (!count)
 		return 0;
 
-	sort(start, count, sizeof(*start),
-	     ftrace_cmp_ips, ftrace_swap_ips);
+	ftrace_sort_mcount_area(start, end);
 
 	start_pg = ftrace_allocate_pages(count);
 	if (!start_pg)
@@ -4965,6 +4991,14 @@ void __init ftrace_init(void)
 	ftrace_disabled = 1;
 }
 
+void __init ftrace_init_early(void)
+{
+	extern unsigned long __start_mcount_loc[];
+	extern unsigned long __stop_mcount_loc[];
+
+	ftrace_sort_mcount_area(__start_mcount_loc, __stop_mcount_loc);
+}
+
 /* Do nothing if arch does not support this */
 void __weak arch_ftrace_update_trampoline(struct ftrace_ops *ops)
 {
-- 
1.8.4

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