使用skyeye运行《Linux设备驱动开发详解》的实例（二）

<a>编译和安装</a>

<a>选中三个模块：</a>

<a>─── driver examples in 'Explain Linux Device Drivers in detail' ─────────────────────────────┐ │ Arrow keys navigate the menu. <Enter> selects submenus ---&gt;. Highlighted letters are hotkeys. Pressing <Y> │ │ includes, <N> excludes, <M> modularizes features. Press <Esc><Esc> to exit, <?> for Help, </> for Search. Legend: │ │ [*] built-in [ ] excluded <M> module < > module capable │ │ │ │ ┌───────────────────────────────────────────────────────────┐ │ │ │ --- driver examples in 'Explain Linux Device Drivers in detail' │ │ │ │ <M> Hello World │ │ │ │ <M> globalmem │ │ │ │ <M> globalfifo │ │ │ │ │ │</a>

<a>在linux-2.6.31下运行：</a>

<a>bhsong@bhsong-laptop:~/develop/svn/ldd6410/linux-2.6.31$ make modules</a>

<a>以loopback方式mount根文件系统，譬如对于skyeye的initrd.img运行如下命令：</a>

<a>...skyeye/training-simulation$ sudo mount -o loop initrd.img initrd</a>

<a>将所有模块安装到根文件系统：</a>

<a>make INSTALL_MOD_PATH=/home/bhsong/develop/training/skyeye/training-simulation/initrd modules_install</a>

<a>请根据你的路径，正确的设置INSTALL_MOD_PATH。安装之后，所有模块以及模块间依赖关系进入根文件系统：</a>

<a>启动Linux，对于skyeye为：</a>

<a>sudo skyeye -e vmlinux -c skyeye-standalone.conf ... Welcome to _ _____ __ __ _ _ / \ / __ \ / \_/ \ | | |_| / _ \ | | | | / /\ /\ \ | | _ ____ _ _ _ _ / /_\ \ | |__| | / / \_/ \ \| | | | _ \| | | |\ \/ / / /___\ \ | |__\ \ | | | || |___ | | |_| | |_| |/ \ /_/ \_\| | \_\|_| |_||_____||_|_| |_|\____|\_/\_/ ARMLinux for Lihacker LDD6410 For further information please check: http://www.lihacker.com/ http://www.linuxdriver.cn/ For technical support, please subscribe mail list [email protected] and post there. The url is http://groups.google.com/group/linuxdriver. #</a>

<a>modprobe hello modprobe globalmem globalmem_major=250 modprobe globalfifo globalfifo_major=251</a>

<a>skyeye对insmod的支持有些问题，加载模块时会出现：</a>

<a># modprobe hello Unable to handle kernel paging request at virtual address bf000000 pgd = c05f0000 [bf000000] *pgd=00000000 Internal error: Oops: 807 [#1] Modules linked in: CPU: 0 Not tainted (2.6.31.6-svn79 #21) PC is at __memzero+0x24/0x80 LR is at 0x0 pc : [<c0107404>] lr : [<00000000>] psr: 20000013 sp : c182bf0c ip : 00000000 fp : 00000005 r10: c2807230 r9 : c2807000 r8 : c2807388 r7 : 00000004 r6 : c2807168 r5 : 00000012 r4 : bf000000 r3 : 00000000 r2 : 00000000 r1 : 00000464 r0 : bf000000 Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user Control: 0000317f Table: c05f0000 DAC: 00000015 Process modprobe (pid: 795, stack limit = 0xc182a270) Stack: (0xc182bf0c to 0xc182c000) bf00: c005fba0 00000979 00000000 c2807518 c2807608 bf20: c28072dc c1139e60 c28078a0 00000010 000000c5 c2807388 c182a000 c2807630 bf40: 00000000 c008c178 00000171 00000000 0015ec79 00000287 00000001 00000008 bf60: 00000000 00000979 0015e2f0 00000000 0015e300 c002bf48 c182a000 00000000 bf80: 00000000 c0060878 c1c1a2c0 c1c2f3a0 00000003 00000979 0015e2f0 0015dfa8 bfa0: 00000080 c002bda0 00000979 0015e2f0 0015e300 00000979 0015e2f0 00000000 bfc0: 00000979 0015e2f0 0015dfa8 00000080 0015e2a0 0015dfbc 00000001 00000000 bfe0: bea65958 bea65948 000177f8 00009350 20000010 0015e300 ab081000 11000006 [<c0107404>] (__memzero+0x24/0x80) from [<00000000>] (0x0) Code: e52de004 e1a0c002 e1a0e002 e2511040 (a8a0500c) ---[ end trace 1e19dcbb1e19dcba ]--- Segmentation fault</a>

# strace modprobe hello

execve("/sbin/modprobe", ["modprobe", "hello"], [/* 7 vars */]) = 0

uname({sys="Linux", node="lihacker", ...}) = 0

brk(0) = 0x15d000

brk(0x15dd02) = 0x15dd02

set_tls(0x15d4a0, 0x1573c0, 0, 0x1, 0x15d4a0) = 0

brk(0x17ed02) = 0x17ed02

brk(0x17f000) = 0x17f000

getuid32() = 0

chdir("/lib/modules") = 0

chdir("2.6.31.6-svn79") = 0

open("/proc/modules", O_RDONLY) = 3

fstat64(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0

mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40000000

read(3, ""..., 1024) = 0

close(3) = 0

munmap(0x40000000, 4096) = 0

lstat64("/etc/modprobe.conf", 0xbe846880) = -1 ENOENT (No such file or directory)

lstat64("/etc/modprobe.d", 0xbe846880) = -1 ENOENT (No such file or directory)

open("modules.dep", O_RDONLY) = 3

fstat64(3, {st_mode=S_IFREG|0644, st_size=17141, ...}) = 0

mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40001000

read(3, "/lib/modules/2.6.31.6-svn79/kerne"..., 1024) = 1024

read(3, "nel/net/netfilter/x_tables.ko\n/li"..., 1024) = 1024

read(3, "/net/netfilter/xt_esp.ko: /lib/mo"..., 1024) = 1024

read(3, "ables.ko /lib/modules/2.6.31.6-sv"..., 1024) = 1024

read(3, "es/2.6.31.6-svn79/kernel/net/netf"..., 1024) = 1024

read(3, ".6-svn79/kernel/net/netfilter/nf_"..., 1024) = 1024

read(3, "b/modules/2.6.31.6-svn79/kernel/n"..., 1024) = 1024

read(3, "etfilter/nf_conntrack_ipv4.ko /li"..., 1024) = 1024

read(3, ".6.31.6-svn79/kernel/net/netfilte"..., 1024) = 1024

read(3, "defrag_ipv4.ko\n/lib/modules/2.6.3"..., 1024) = 1024

read(3, "tfilter/nf_conntrack_ipv4.ko /lib"..., 1024) = 1024

read(3, ".6-svn79/kernel/net/ipv4/netfilte"..., 1024) = 1024

read(3, "1.6-svn79/kernel/net/netfilter/x_"..., 1024) = 1024

read(3, "ib/modules/2.6.31.6-svn79/kernel/"..., 1024) = 1024

read(3, "o:\n/lib/modules/2.6.31.6-svn79/ke"..., 1024) = 757

munmap(0x40001000, 4096) = 0

open("/lib/modules/2.6.31.6-svn79/kernel/drivers/char/driver_examples/hello.ko", O_RDONLY) = 3

fstat64(3, {st_mode=S_IFREG|0644, st_size=2425, ...}) = 0

read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\1\0(\0\1\0\0\0\0\0\0\0\0\0\0\0\210"..., 3072) = 2425

read(3, ""..., 647) = 0

init_module(0x15e300, 2425, ""Unable to handle kernel paging request at virtual address bf000000

pgd = c0620000

[bf000000] *pgd=00000000

Internal error: Oops: 807 [#1]

Modules linked in:

CPU: 0 Not tainted (2.6.31.6-svn79 #21)

PC is at __memzero+0x24/0x80

LR is at 0x0

pc : [<c0107404>] lr : [<00000000>] psr: 20000013

sp : c069ff0c ip : 00000000 fp : 00000005

r10: c2807230 r9 : c2807000 r8 : c2807388

r7 : 00000004 r6 : c2807168 r5 : 00000012 r4 : bf000000

r3 : 00000000 r2 : 00000000 r1 : 00000464 r0 : bf000000

Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user

Control: 0000317f Table: c0620000 DAC: 00000015

Process modprobe (pid: 796, stack limit = 0xc069e270)

Stack: (0xc069ff0c to 0xc06a0000)

ff00: c005fba0 00000000 00000000 c2807518 c2807608

ff20: c28072dc c1139240 c28078a0 00000010 00000000 c2807388 00000000 c2807630

ff40: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000

ff60: 00000000 00000979 0015e2f0 00000000 0015e300 c002bf48 c069e000 00000000

ff80: 00000000 c0060878 be846958 c002dbe0 00000000 00000979 0015e2f0 0015dfa8

ffa0: 00000080 c002bf0c 00000979 0015e2f0 0015e300 00000979 0015e2f0 00000000

ffc0: 00000979 0015e2f0 0015dfa8 00000080 0015e2a0 0015dfbc 00000001 00000000

ffe0: be846958 be846948 000177f8 00009350 20000010 0015e300 ebff1fc9 e3500000

[<c0107404>] (__memzero+0x24/0x80) from [<00000000>] (0x0)

Code: e52de004 e1a0c002 e1a0e002 e2511040 (a8a0500c)

---[ end trace 1e19dcbb1e19dcba ]---

+++ killed by SIGSEGV +++

很明显，死在内核的linux-2.6.31/kernel/module.c的init_module()函数中,加上几个printk:

2453 SYSCALL_DEFINE3(init_module, void __user *, umod,

2454 unsigned long, len, const char __user *, uargs)

2455 {

2456 struct module *mod;

2457 int ret = 0;

2458

2459 printk("%s %d\n", __func__, __LINE__);

2460

2461 /* Must have permission */

2462 if (!capable(CAP_SYS_MODULE) || modules_disabled)

2463 return -EPERM;

2464

2465 +printk("%s %d\n", __func__, __LINE__);

2466

2467 /* Only one module load at a time, please */

2468 if (mutex_lock_interruptible(&module_mutex) != 0)

2469 return -EINTR;

2470

2471 +printk("%s %d\n", __func__, __LINE__);

2472

2473 /* Do all the hard work */

2474 mod = load_module(umod, len, uargs);

2475 if (IS_ERR(mod)) {

2476 mutex_unlock(&module_mutex);

2477 return PTR_ERR(mod);

2478 }

2479

2480 +printk("%s %d\n", __func__, __LINE__);

2481

再次运行:

# modprobe hello

sys_init_module 2459

sys_init_module 2465

sys_init_module 2471

Unable to handle kernel paging request at virtual address bf000000

pgd = c05f0000

从打印信息可以看出，panic发生在load_module函数，既然"sys_init_module 2471"被打印而"sys_init_module 2480"未打印。继续跟进load_module()，直到最后发现内核崩溃在memset(ptr, 0, mod-&gt;core_size);：

static noinline struct module *load_module(void __user *umod,

unsigned long len,

const char __user *uargs)

{

...

ptr = module_alloc_update_bounds(mod-&gt;core_size);

kmemleak_not_leak(ptr);

memset(ptr, 0, mod-&gt;core_size);

一路跟踪源代码，发现ARM的Kernel会将模块的内存申请在3G-16M到3G的区域，而skyeye在内核空间处理3G以下地址的时候，会发生错误:

"Unable to handle kernel paging request at virtual address bf000000"

因此，workaround掉这个bug:

Index: arch/arm/kernel/module.c

===================================================================

--- arch/arm/kernel/module.c (revision 87)

+++ arch/arm/kernel/module.c (working copy)

@@ -38,7 +38,7 @@

#ifdef CONFIG_MMU

void *module_alloc(unsigned long size)

- struct vm_struct *area;

+ /*struct vm_struct *area;

size = PAGE_ALIGN(size);

if (!size)

@@ -49,6 +49,9 @@

return NULL;

return __vmalloc_area(area, GFP_KERNEL, PAGE_KERNEL_EXEC);

+*/

+ return size == 0 ? NULL : kmalloc(size, GFP_KERNEL);

}

#else /* CONFIG_MMU */

@@ -59,7 +62,7 @@

void module_free(struct module *module, void *region)

- vfree(region);

+ kfree(region);

int module_frob_arch_sections(Elf_Ehdr *hdr,

由于此workaround使用了kmalloc，如果内核模块很大，kmalloc申请的内存不够存放，则可以修改： include/linux/slab.h中的KMALLOC_SHIFT_HIGH宏定义。另外，此workaround成立的条件是mem=32M或小于32M。现在我们可以自由地加载模块了，看看结果：

加载模块：

Hello World enter

# modprobe globalmem globalmem_major=250

# modprobe globalfifo globalfifo_major=251

查看加载的模块:

# lsmod

Not tainted

globalmem 3356 0 - Live 0xc0f66000

hello 1188 0 - Live 0xc1128000

globalfifo 4292 0 - Live 0xc182a000

查看设备：

# cat /proc/devices

Character devices:

1 mem

2 pty

3 ttyp

4 /dev/vc/0

4 tty

4 ttyS

5 /dev/tty

5 /dev/console

5 /dev/ptmx

7 vcs

10 misc

13 input

21 sg

29 fb

128 ptm

136 pts

204 s3c2410_serial

250 globalmem

251 globalfifo

建立结点：

# mknod /dev/globalmem c 250 0

# mknod /dev/globalfifo c 251 0

读写设备文件：

# echo "hello, cisco" &gt; /dev/globalmem

written 13 bytes(s) from 0

# cat /dev/globalmem

read 4096 bytes(s) from 0

hello, cisco

# cat /dev/globalfifo &

# echo "hello,Linux, I love you" &gt; /dev/globalfifo

written 24 bytes(s),current_len:24

# read 24 bytes(s),current_len:0

hello,cisco, I love you

本文转自 21cnbao 51CTO博客，原文链接：http://blog.51cto.com/21cnbao/283418，如需转载请自行联系原作者

使用skyeye运行《Linux设备驱动开发详解》的实例（二）

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