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对于2.6.31及以上的内核，gcov已经默认支持：http://kernelnewbies.org/Linux_2_6_31#head-1c98f5fae2cb7f0fa65bb6de08d7c5c6475180a8
也就是不用再打补丁，执行make menuconfig，选中如下选项：
General setup —>
GCOV-based kernel profiling —>
[*] Enable gcov-based kernel profiling
[*] Profile entire Kernel

[root@localhost linux-2.6.38.8]# cat .config | grep GCOV
# GCOV-based kernel profiling
CONFIG_GCOV_KERNEL=y
CONFIG_GCOV_PROFILE_ALL=y
[root@localhost linux-2.6.38.8]#

编译安装这个内核：

[root@localhost linux-2.6.38.8]# make; make modules;make modules_install;make install;

重启机器后，mount加载debugfs文件系统，并调用gcov对相应文件做覆盖测量：

[root@localhost ~]# mount -t debugfs none /sys/kernel/debug
[root@localhost ~]# cd /usr/src/linux-2.6.38.8
[root@localhost linux-2.6.38.8]# gcov kernel/gcov/base.c -o /sys/kernel/debug/gcov/usr/src/linux-2.6.38.8/kernel/gcov/
File 'kernel/gcov/base.c'
Lines executed:80.00% of 45
kernel/gcov/base.c:creating 'base.c.gcov'

[root@localhost linux-2.6.38.8]#

查看结果：

[root@localhost linux-2.6.38.8]# cat base.c.gcov
        -:    0:Source:kernel/gcov/base.c
        -:    0:Graph:/sys/kernel/debug/gcov/usr/src/linux-2.6.38.8/kernel/gcov/base.gcno
        -:    0:Data:/sys/kernel/debug/gcov/usr/src/linux-2.6.38.8/kernel/gcov/base.gcda
        -:    0:Runs:0
        -:    0:Programs:0
        -:    1:/*
        -:    2: *  This code maintains a list of active profiling data structures.
        -:    3: *
        -:    4: *    Copyright IBM Corp. 2009
        -:    5: *    Author(s): Peter Oberparleiter <[email protected]>
        -:    6: *
        -:    7: *    Uses gcc-internal data definitions.
        -:    8: *    Based on the gcov-kernel patch by:
        -:    9: *               Hubertus Franke <[email protected]>
        -:   10: *               Nigel Hinds <[email protected]>
        -:   11: *               Rajan Ravindran <[email protected]>
        -:   12: *               Peter Oberparleiter <[email protected]>
        -:   13: *               Paul Larson
        -:   14: */
        -:   15:
        -:   16:#define pr_fmt(fmt)     "gcov: " fmt
        -:   17:
        -:   18:#include <linux/init.h>
        -:   19:#include <linux/module.h>
        -:   20:#include <linux/mutex.h>
        -:   21:#include "gcov.h"
        -:   22:
        -:   23:static struct gcov_info *gcov_info_head;
        -:   24:static int gcov_events_enabled;
        -:   25:static DEFINE_MUTEX(gcov_lock);
        -:   26:
        -:   27:/*
        -:   28: * __gcov_init is called by gcc-generated constructor code for each object
        -:   29: * file compiled with -fprofile-arcs.
        -:   30: */
     1617:   31:void __gcov_init(struct gcov_info *info)
        -:   32:{
        -:   33:        static unsigned int gcov_version;
        -:   34:
     1617:   35:        mutex_lock(&gcov_lock);
     1617:   36:        if (gcov_version == 0) {
        1:   37:                gcov_version = info->version;
        -:   38:                /*
        -:   39:                 * Printing gcc's version magic may prove useful for debugging
        -:   40:                 * incompatibility reports.
        -:   41:                 */
        1:   42:                pr_info("version magic: 0x%x\n", gcov_version);
        -:   43:        }
        -:   44:        /*
        -:   45:         * Add new profiling data structure to list and inform event
        -:   46:         * listener.
        -:   47:         */
     1617:   48:        info->next = gcov_info_head;
     1617:   49:        gcov_info_head = info;
     1617:   50:        if (gcov_events_enabled)
      257:   51:                gcov_event(GCOV_ADD, info);
     1617:   52:        mutex_unlock(&gcov_lock);
     1617:   53:}
        -:   54:EXPORT_SYMBOL(__gcov_init);
        -:   55:
        -:   56:/*
        -:   57: * These functions may be referenced by gcc-generated profiling code but serve
        -:   58: * no function for kernel profiling.
        -:   59: */
    #####:   60:void __gcov_flush(void)
        -:   61:{
        -:   62:        /* Unused. */
    #####:   63:}
        -:   64:EXPORT_SYMBOL(__gcov_flush);
        -:   65:
    #####:   66:void __gcov_merge_add(gcov_type *counters, unsigned int n_counters)
        -:   67:{
        -:   68:        /* Unused. */
    #####:   69:}
        -:   70:EXPORT_SYMBOL(__gcov_merge_add);
        -:   71:
    #####:   72:void __gcov_merge_single(gcov_type *counters, unsigned int n_counters)
        -:   73:{
        -:   74:        /* Unused. */
    #####:   75:}
        -:   76:EXPORT_SYMBOL(__gcov_merge_single);
        -:   77:
    #####:   78:void __gcov_merge_delta(gcov_type *counters, unsigned int n_counters)
        -:   79:{
        -:   80:        /* Unused. */
    #####:   81:}
        -:   82:EXPORT_SYMBOL(__gcov_merge_delta);
        -:   83:
        -:   84:/**
        -:   85: * gcov_enable_events - enable event reporting through gcov_event()
        -:   86: *
        -:   87: * Turn on reporting of profiling data load/unload-events through the
        -:   88: * gcov_event() callback. Also replay all previous events once. This function
        -:   89: * is needed because some events are potentially generated too early for the
        -:   90: * callback implementation to handle them initially.
        -:   91: */
        1:   92:void gcov_enable_events(void)
        -:   93:{
        -:   94:        struct gcov_info *info;
        -:   95:
        1:   96:        mutex_lock(&gcov_lock);
        1:   97:        gcov_events_enabled = 1;
        -:   98:        /* Perform event callback for previously registered entries. */
     1361:   99:        for (info = gcov_info_head; info; info = info->next)
     1360:  100:                gcov_event(GCOV_ADD, info);
        1:  101:        mutex_unlock(&gcov_lock);
        1:  102:}
        -:  103:
        -:  104:#ifdef CONFIG_MODULES
        -:  105:static inline int within(void *addr, void *start, unsigned long size)
        -:  106:{
    13666:  107:        return ((addr >= start) && (addr < start + size));
        -:  108:}
        -:  109:
        -:  110:/* Update list and generate events when modules are unloaded. */
      158:  111:static int gcov_module_notifier(struct notifier_block *nb, unsigned long event,
        -:  112:                                void *data)
        -:  113:{
      158:  114:        struct module *mod = data;
        -:  115:        struct gcov_info *info;
        -:  116:        struct gcov_info *prev;
        -:  117:
      158:  118:        if (event != MODULE_STATE_GOING)
      149:  119:                return NOTIFY_OK;
        9:  120:        mutex_lock(&gcov_lock);
        9:  121:        prev = NULL;
        -:  122:        /* Remove entries located in module from linked list. */
    13675:  123:        for (info = gcov_info_head; info; info = info->next) {
    27332:  124:                if (within(info, mod->module_core, mod->core_size)) {
        9:  125:                        if (prev)
    #####:  126:                                prev->next = info->next;
        -:  127:                        else
        9:  128:                                gcov_info_head = info->next;
        9:  129:                        if (gcov_events_enabled)
        9:  130:                                gcov_event(GCOV_REMOVE, info);
        -:  131:                } else
    13657:  132:                        prev = info;
        -:  133:        }
        9:  134:        mutex_unlock(&gcov_lock);
        -:  135:
        9:  136:        return NOTIFY_OK;
        -:  137:}
        -:  138:
        -:  139:static struct notifier_block gcov_nb = {
        -:  140:        .notifier_call  = gcov_module_notifier,
        -:  141:};
        -:  142:
        1:  143:static int __init gcov_init(void)
        -:  144:{
        1:  145:        return register_module_notifier(&gcov_nb);
        -:  146:}
        -:  147:device_initcall(gcov_init);
        -:  148:#endif /* CONFIG_MODULES */
[root@localhost linux-2.6.38.8]#

试试其他文件：

[root@localhost linux-2.6.38.8]# gcov /usr/src/linux-2.6.38.8/drivers/net/e1000/e1000_main.c -o /sys/kernel/debug/gcov/usr/src/linux-2.6.38.8/drivers/net/e1000/
[root@localhost linux-2.6.38.8]# ls *.gcov
atomic.h.gcov              getorder.h.gcov   irqflags.h.gcov   skbuff.h.gcov
bitops.h.gcov              gfp.h.gcov        kobject.h.gcov    slab.h.gcov
checksum_64.h.gcov         highmem.h.gcov    list.h.gcov       slub_def.h.gcov
device.h.gcov              if_vlan.h.gcov    mii.h.gcov        spinlock.h.gcov
dma-mapping-common.h.gcov  interrupt.h.gcov  mm.h.gcov         tcp.h.gcov
dma-mapping.h.gcov         io.h.gcov         netdevice.h.gcov  thread_info.h.gcov
e1000_main.c.gcov          ip.h.gcov         paravirt.h.gcov   uaccess.h.gcov
etherdevice.h.gcov         ipv6.h.gcov       pci.h.gcov
[root@localhost linux-2.6.38.8]# head e1000_main.c.gcov
        -:    0:Source:drivers/net/e1000/e1000_main.c
        -:    0:Graph:/sys/kernel/debug/gcov/usr/src/linux-2.6.38.8/drivers/net/e1000/e1000_main.gcno
        -:    0:Data:/sys/kernel/debug/gcov/usr/src/linux-2.6.38.8/drivers/net/e1000/e1000_main.gcda
        -:    0:Runs:0
        -:    0:Programs:0
        -:    1:/*******************************************************************************
        -:    2:
        -:    3:  Intel PRO/1000 Linux driver
        -:    4:  Copyright(c) 1999 - 2006 Intel Corporation.
        -:    5:
[root@localhost linux-2.6.38.8]#

的确OK。值得注意的是，不能切换当前目录，否则得到的e1000_main.c.gcov没有源代码，全是EOF（一开始，我看把我的内核源码目录 /usr/src/linux-2.6.38.8/搞得很混乱，所以切换当前目录到/tmp目录，结果发现生成的文件没有对应的源代码）：

[root@localhost tmp]# head e1000_main.c.gcov
        -:    0:Source:drivers/net/e1000/e1000_main.c
        -:    0:Graph:/sys/kernel/debug/gcov/usr/src/linux-2.6.38.8/drivers/net/e1000/e1000_main.gcno
        -:    0:Data:/sys/kernel/debug/gcov/usr/src/linux-2.6.38.8/drivers/net/e1000/e1000_main.gcda
        -:    0:Runs:0
        -:    0:Programs:0
        -:    1:/*EOF*/
        -:    2:/*EOF*/
        -:    3:/*EOF*/
        -:    4:/*EOF*/
        -:    5:/*EOF*/

试试自定义模块：

[root@localhost module_test]# cat module_test.c 

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>

#define OOPSTIMEOUT 100
static unsigned long start_time;

static unsigned int fun_hook(unsigned int hooknum,
                struct sk_buff *skb,
                const struct net_device *in,
                const struct net_device *out,
                int (*okfn)(struct sk_buff *))
{
        printk(KERN_DEBUG "skb data len: %u\n", skb->len);

        return NF_ACCEPT;
}

static struct nf_hook_ops nf_ops = {
        .hook = fun_hook,
        .owner = THIS_MODULE,
        .pf = NFPROTO_IPV4,
        .hooknum = NF_INET_PRE_ROUTING,
        .priority = NF_IP_PRI_NAT_DST,
};

static int __init module_test_init(void)
{
        int ret = 0;
        start_time = jiffies;

        ret = nf_register_hook(&nf_ops);
        if (ret < 0) {
                printk("error register hook %d.\n", ret);
                return ret;
        }
        printk("insmod ok, start_time: %lu.\n", start_time);

        return 0;
}

static void __exit module_test_exit(void)
{
        nf_unregister_hook(&nf_ops);
        return;
}

module_init(module_test_init);
module_exit(module_test_exit);

MODULE_LICENSE("GPL");

[root@localhost module_test]# cat Makefile
# Makefile

MDIR = $(shell pwd)

ifeq (, $(KSRC))
        KSRC := /usr/src/linux-`uname -r`
endif

ifeq (, $(PROJECT_DIR))
        PROJECT_DIR := $(PWD)/../
endif

module := module_test

obj-m := $(module).o

srcs =  $(wildcard, *.c)

$(module)-objs := $(addsuffix .o, $(basename $(srcs)))

EXTRA_CFLAGS += -g $(FLAG) -I$(PROJECT_DIR)/inc -I${SHAREDHDR} -I$(KERNELHDR) -O2 -D__KERNEL__ -DMODULE $(INCLUDE) -DEXPORT_SYMTAB

TARGET = $(module).ko

all:
        make -C $(KSRC) M=$(MDIR) modules

debug:
        make EXTRA_FLAGS="${EXTRA_CFLAGS} -DDEBUG" -C $(KSRC) M=$(MDIR) modules

clean:
        make -C $(KSRC) M=$(MDIR) clean

install: all
        cp -f $(TARGET) $(INSTALL_DIR)
[root@localhost module_test]# make
make -C /usr/src/linux-`uname -r` M=/home/gcov/module_test modules
make[1]: Entering directory `/usr/src/linux-2.6.38.8'
  CC [M]  /home/gcov/module_test/module_test.o
  Building modules, stage 2.
  MODPOST 1 modules
  CC      /home/gcov/module_test/module_test.mod.o
  LD [M]  /home/gcov/module_test/module_test.ko
make[1]: Leaving directory `/usr/src/linux-2.6.38.8'
[root@localhost module_test]# insmod module_test.ko

看结果：

[root@localhost module_test]# gcov /home/gcov/module_test/module_test.c -o /sys/kernel/debug/gcov/home/gcov/module_test/
File '/home/gcov/module_test/module_test.c'
Lines executed:71.43% of 14
/home/gcov/module_test/module_test.c:creating 'module_test.c.gcov'

[root@localhost module_test]# cat module_test.c.gcov
        -:    0:Source:/home/gcov/module_test/module_test.c
        -:    0:Graph:/sys/kernel/debug/gcov/home/gcov/module_test/module_test.gcno
        -:    0:Data:/sys/kernel/debug/gcov/home/gcov/module_test/module_test.gcda
        -:    0:Runs:0
        -:    0:Programs:0
        -:    1:
        -:    2:#include <linux/kernel.h>
        -:    3:#include <linux/module.h>
        -:    4:#include <linux/netfilter.h>
        -:    5:#include <linux/netfilter_ipv4.h>
        -:    6:
        -:    7:#define OOPSTIMEOUT 100
        -:    8:static unsigned long start_time;
        -:    9:
       37:   10:static unsigned int fun_hook(unsigned int hooknum,
        -:   11:                struct sk_buff *skb,
        -:   12:                const struct net_device *in,
        -:   13:                const struct net_device *out,
        -:   14:                int (*okfn)(struct sk_buff *))
        -:   15:{
       37:   16:        printk(KERN_DEBUG "skb data len: %u\n", skb->len);
        -:   17:
       37:   18:        return NF_ACCEPT;
        -:   19:}
        -:   20:
        -:   21:static struct nf_hook_ops nf_ops = {
        -:   22:        .hook = fun_hook,
        -:   23:        .owner = THIS_MODULE,
        -:   24:        .pf = NFPROTO_IPV4,
        -:   25:        .hooknum = NF_INET_PRE_ROUTING,
        -:   26:        .priority = NF_IP_PRI_NAT_DST,
        -:   27:};
        -:   28:
        1:   29:static int __init module_test_init(void)
        -:   30:{
        1:   31:        int ret = 0;
        1:   32:        start_time = jiffies;
        -:   33:
        1:   34:        ret = nf_register_hook(&nf_ops);
        1:   35:        if (ret < 0) {
    #####:   36:                printk("error register hook %d.\n", ret);
    #####:   37:                return ret;
        -:   38:        }
        1:   39:        printk("insmod ok, start_time: %lu.\n", start_time);
        -:   40:
        1:   41:        return 0;
        -:   42:}
        -:   43:
    #####:   44:static void __exit module_test_exit(void)
        -:   45:{
    #####:   46:        nf_unregister_hook(&nf_ops);
        -:   47:        return;
        -:   48:}
        -:   49:
        -:   50:module_init(module_test_init);
        -:   51:module_exit(module_test_exit);
        -:   52:
        -:   53:MODULE_LICENSE("GPL");
        -:   54:
[root@localhost module_test]#

完全参考：http://ltp.sourceforge.net/coverage/gcov.php

转载请保留地址：http://lenky.info/archives/2012/08/24/1888 或 http://lenky.info/?p=1888

---

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