最近在调式一个判断nand是好的还是坏的驱动+测试程序，于是有了以下的调式过程，似乎自己也学到了一点知识，所以记录一下。
这篇文章主要是讲述调式驱动的一个方法而已。
先来看看测试程序
#include <string.h>
#include <errno.h>
#include "dragonboard_inc.h"
#include <sys/ioctl.h>
#include <linux/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
/* just define an ioctl cmd for nand test*/
#define DRAGON_BOARD_TEST _IO('V',55)
int main(int argc, char *argv[])
{
char filename[256];
int fd;
int retval = -1;
if (argc == 2) {
strncpy(filename, argv[1], 256);
}
else {
db_error("Usage: nandrw FILE
");
retval = -1;
}
/* open file */
fd = open(filename, O_RDWR);
printf("filename is %s
",filename);
printf("nand fd = %d
",fd);
if (fd < 0) {
db_error("can't open %s(%s)
", filename, strerror(errno));
retval = -1;
}
/* if nand ok,return 0;otherwise,return -1 */
retval = ioctl(fd, DRAGON_BOARD_TEST);
printf("ioctl_retval = %d
",retval);
if (retval < 0) {
db_error("error in ioctl(%s)......
", strerror(errno));
return retval;
}
/* TEST OK */
return retval;
}测试用例很简单，先打开/dev/nanda的设备节点，用于返回fd给ioctl用， ioctl里的cmd = DRAGON_BOARD_TEST，这是底层实现。
ioctl调用完了就返回，如果返回0表示nand是好的，否则表示nand是坏的。底层如何实现，我就不细说了。
这里需要提的是，测试用例并没有主动调用close(fd)，但是，但是，但是，你万万不要忘了，系统是会自动回收的，系统会帮你调用close函数。
于是有了下面这个bug 的log信息：
[ 7.947228] Unable to handle kernel paging request at virtual address ed9f4b00 [ 7.956339] pgd = d78a8000 [ 7.956876] [ed9f4b00] *pgd=00000000 [ 7.956876] Internal error: Oops: 80000005 [#1] PREEMPT SMP ARM [ 7.956876] Modules linked in: sunxi_keyboard ft5x_ts nand(O) lcd disp [ 7.956876] CPU: 0 Tainted: G O (3.4.39 #21) [ 7.956876] PC is at 0xed9f4b00 [ 7.956876] LR is at nand_blk_release+0x24/0x28 [nand] [ 7.956876] pc : [<ed9f4b00>] lr : [<bf116ed4>] psr: a0000033 [ 7.956876] sp : d76abe08 ip : d76abe18 fp : d76abe14 [ 7.956876] r10: d7dc5998 r9 : d7740a90 r8 : d7c02650 [ 7.956876] r7 : d7854000 r6 : 0000001f r5 : bf11719c r4 : bf14b828 [ 7.956876] r3 : ed9f4b01 r2 : d76abe00 r1 : 0000ffff r0 : d7854400 [ 7.956876] Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA Thumb Segment user [ 7.956876] Control: 10c5387d Table: 578a806a DAC: 00000015 [ 7.956876] [ 7.956876] PC: 0xed9f4a80: [ 7.956876] 4a80 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4aa0 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4ac0 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4ae0 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4b00 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4b20 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4b40 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4b60 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] [ 7.956876] SP: 0xd76abd88: [ 7.956876] bd88 c09a7b40 c0e769e4 d76abdb4 d76abda0 c0062dec c0085640 ed9f4b00 a0000033 [ 7.956876] bda8 ffffffff d76abdf4 d76abe14 d76abdc0 c0010438 c000a25c d7854400 0000ffff [ 7.956876] bdc8 d76abe00 ed9f4b01 bf14b828 bf11719c 0000001f d7854000 d7c02650 d7740a90 [ 7.956876] bde8 d7dc5998 d76abe14 d76abe18 d76abe08 bf116ed4 ed9f4b00 a0000033 ffffffff [ 7.956876] be08 d76abe2c d76abe18 bf1171c8 bf116ebc bf14b7f8 d7c02640 d76abe5c d76abe30 [ 7.956876] be28 c0134da0 bf1171a8 d7c027a0 d7c02640 0000001f d7c02650 d7776688 00000000 [ 7.956876] be48 d7740a90 d7dc5998 d76abe7c d76abe60 c0134f5c c0134ce0 d7776680 d780f070 [ 7.956876] be68 00000008 d7776688 d76abe8c d76abe80 c0134f94 c0134e44 d76abec4 d76abe90 [ 7.956876] [ 7.956876] IP: 0xd76abd98: [ 7.956876] bd98 c0062dec c0085640 ed9f4b00 a0000033 ffffffff d76abdf4 d76abe14 d76abdc0 [ 7.956876] bdb8 c0010438 c000a25c d7854400 0000ffff d76abe00 ed9f4b01 bf14b828 bf11719c [ 7.956876] bdd8 0000001f d7854000 d7c02650 d7740a90 d7dc5998 d76abe14 d76abe18 d76abe08 [ 7.956876] bdf8 bf116ed4 ed9f4b00 a0000033 ffffffff d76abe2c d76abe18 bf1171c8 bf116ebc [ 7.956876] be18 bf14b7f8 d7c02640 d76abe5c d76abe30 c0134da0 bf1171a8 d7c027a0 d7c02640 [ 7.956876] be38 0000001f d7c02650 d7776688 00000000 d7740a90 d7dc5998 d76abe7c d76abe60 [ 7.956876] be58 c0134f5c c0134ce0 d7776680 d780f070 00000008 d7776688 d76abe8c d76abe80 [ 7.956876] be78 c0134f94 c0134e44 d76abec4 d76abe90 c01045a8 c0134f78 00000000 00000000 [ 7.956876] [ 7.956876] FP: 0xd76abd94: [ 7.956876] bd94 d76abda0 c0062dec c0085640 ed9f4b00 a0000033 ffffffff d76abdf4 d76abe14 [ 7.956876] bdb4 d76abdc0 c0010438 c000a25c d7854400 0000ffff d76abe00 ed9f4b01 bf14b828 [ 7.956876] bdd4 bf11719c 0000001f d7854000 d7c02650 d7740a90 d7dc5998 d76abe14 d76abe18 [ 7.956876] bdf4 d76abe08 bf116ed4 ed9f4b00 a0000033 ffffffff d76abe2c d76abe18 bf1171c8 [ 7.956876] be14 bf116ebc bf14b7f8 d7c02640 d76abe5c d76abe30 c0134da0 bf1171a8 d7c027a0 [ 7.956876] be34 d7c02640 0000001f d7c02650 d7776688 00000000 d7740a90 d7dc5998 d76abe7c [ 7.956876] be54 d76abe60 c0134f5c c0134ce0 d7776680 d780f070 00000008 d7776688 d76abe8c [ 7.956876] be74 d76abe80 c0134f94 c0134e44 d76abec4 d76abe90 c01045a8 c0134f78 00000000 [ 7.956876] [ 7.956876] R0: 0xd7854380: [ 7.956876] 4380 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 43a0 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 43c0 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 43e0 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 4400 bf14b828 ee367b0e ee205b07 ee376b02 eeb5cb05 ee311bc0 eef18b06 ee0efa10 [ 7.956876] 4420 bf48cb0e 5b41eeb1 eeb0d401 eeb55b41 eef16bc0 bf48fa10 7b46eeb1 eeb0d401 [ 7.956876] 4440 eeb47b46 eef15bc7 f301fa10 ee36839e 4bda7b48 ed93447b ee316b00 ed9d7b07 [ 7.956876] 4460 ee371b02 ee317b06 ee399b07 ed9f4b08 4bd37bc0 ed93447b ee201b00 ee246b07 [ 7.956876] [ 7.956876] R2: 0xd76abd80: [ 7.956876] bd80 00000000 c00d09b4 c09a7b40 c0e769e4 d76abdb4 d76abda0 c0062dec c0085640 [ 7.956876] bda0 ed9f4b00 a0000033 ffffffff d76abdf4 d76abe14 d76abdc0 c0010438 c000a25c [ 7.956876] bdc0 d7854400 0000ffff d76abe00 ed9f4b01 bf14b828 bf11719c 0000001f d7854000 [ 7.956876] bde0 d7c02650 d7740a90 d7dc5998 d76abe14 d76abe18 d76abe08 bf116ed4 ed9f4b00 [ 7.956876] be00 a0000033 ffffffff d76abe2c d76abe18 bf1171c8 bf116ebc bf14b7f8 d7c02640 [ 7.956876] be20 d76abe5c d76abe30 c0134da0 bf1171a8 d7c027a0 d7c02640 0000001f d7c02650 [ 7.956876] be40 d7776688 00000000 d7740a90 d7dc5998 d76abe7c d76abe60 c0134f5c c0134ce0 [ 7.956876] be60 d7776680 d780f070 00000008 d7776688 d76abe8c d76abe80 c0134f94 c0134e44 [ 7.956876] [ 7.956876] R3: 0xed9f4a81: [ 7.956876] 4a80 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4aa0 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4ac0 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4ae0 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4b00 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4b20 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4b40 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4b60 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] 4b80 ******** ******** ******** ******** ******** ******** ******** ******** [ 7.956876] [ 7.956876] R7: 0xd7853f80: [ 7.956876] 3f80 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 3fa0 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 3fc0 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 3fe0 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 4000 0000005d 00000000 00000001 646e616e 00000061 00000000 00000000 00000000 [ 7.956876] 4020 00000000 00000000 00000000 00000000 00000000 00000000 d777c880 00000000 [ 7.956876] 4040 00000000 00000000 00000200 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 4060 00000000 d79e4f40 d777c640 d776a22c d79e5e0c d81b3b40 d80c3d00 c097e5c8 [ 7.956876] [ 7.956876] R8: 0xd7c025d0: [ 7.956876] 25d0 00000000 00000000 d7c025d8 d7c025d8 00000000 00000000 00000000 c06496fc [ 7.956876] 25f0 000200d0 d7761b70 00000000 00000000 d7c02600 d7c02600 00000000 d7c0260c [ 7.956876] 2610 d7c0260c d7c02440 00000000 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 2630 00000000 00000000 00000000 00000000 05d00000 00000000 d7c026d0 00000000 [ 7.956876] 2650 00000000 00000000 00000000 d7c0265c d7c0265c d78e73c0 d780f1ac d780f1ac [ 7.956876] 2670 00000000 00000000 00000000 00000000 d7c02680 d7c02680 d7c02640 00001000 [ 7.956876] 2690 d7854040 00000000 00000000 d7854000 d760c078 d7c02aa4 c096d70c 00000000 [ 7.956876] 26b0 00000000 00000001 00000000 00000000 d7c026c0 d7c026c0 00000000 00000000 [ 7.956876] [ 7.956876] R9: 0xd7740a10: [ 7.956876] 0a10 d7740a10 d7740a10 d7740a18 d7740a18 d7740a20 d7740a20 00000000 d800ba40 [ 7.956876] 0a30 00000000 00000000 00000017 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 0a50 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 0a70 00000000 00000000 00000000 00000000 d801fd00 d801fd00 d8021380 d7d26aa8 [ 7.956876] 0a90 d7c01f70 d810dc00 00000020 c0940774 00000001 d7740cec d7740cec d80212ec [ 7.956876] 0ab0 d7740dac d810dc8c d7740f34 d781aec0 d7740d00 d7740dc0 d7740ac8 d7740ac8 [ 7.956876] 0ad0 d7740ad0 d7740ad0 d7740ad8 d7740ad8 d7740ae0 d7740ae0 00000000 d800ba40 [ 7.956876] 0af0 00000000 00000000 00000014 00000000 00000000 00000000 00000000 00000000 [ 7.956876] [ 7.956876] R10: 0xd7dc5918: [ 7.956876] 5918 d7cda1a8 c12872e0 d7dc52b0 bf51d0bd 0000000f d7dc5934 d7e0ce58 74736574 [ 7.956876] 5938 6e6f635f 2e676966 00786566 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 5958 00000000 00000000 00000000 c0652fc0 d782fc00 00000002 00000000 d782fc94 [ 7.956876] 5978 d782fc94 d7dc5324 d7dc5324 d7dc5984 d7dc5984 d7e0cefc d7e0cefc 00000000 [ 7.956876] 5998 00000088 00000004 00000000 c128ba94 d7c01f70 12770052 00000005 d7dc59bc [ 7.956876] 59b8 d780f070 646e616e 00000061 00000000 00000000 00000000 00000000 00000000 [ 7.956876] 59d8 00000000 00000000 00000002 00000000 00000000 c0648a40 d810dc00 00000000 [ 7.956876] 59f8 00000000 d7dc59fc d7dc59fc d7d2a20c d7d23d34 d7dc5a0c d7dc5a0c d780f114 [ 7.956876] Process nandrw (pid: 159, stack limit = 0xd76aa2f8) [ 7.956876] Stack: (0xd76abe08 to 0xd76ac000) [ 7.956876] be00: d76abe2c d76abe18 bf1171c8 bf116ebc bf14b7f8 d7c02640 [ 7.956876] be20: d76abe5c d76abe30 c0134da0 bf1171a8 d7c027a0 d7c02640 0000001f d7c02650 [ 7.956876] be40: d7776688 00000000 d7740a90 d7dc5998 d76abe7c d76abe60 c0134f5c c0134ce0 [ 7.956876] be60: d7776680 d780f070 00000008 d7776688 d76abe8c d76abe80 c0134f94 c0134e44 [ 7.956876] be80: d76abec4 d76abe90 c01045a8 c0134f78 00000000 00000000 d76abec4 d7776680 [ 7.956876] bea0: 00000000 d8038380 d8038388 00000028 d76aa000 00000000 d76abee4 d76abec8 [ 7.956876] bec0: c0100dc4 c0104494 d80383fc d8038380 00000000 00000001 d76abf0c d76abee8 [ 7.956876] bee0: c00397cc c0100d50 d78e73c0 d8038380 d78e7680 000000f8 c00109e8 00000000 [ 7.956876] bf00: d76abf2c d76abf10 c00398c0 c0039738 00800000 d78e73c0 00000000 d76aa000 [ 7.956876] bf20: d76abf74 d76abf30 c0039b80 c0039884 d76abf6c 00000001 c0102b08 c013ae84 [ 7.956876] bf40: 00000000 00000000 d76abf64 d793eb80 00000000 d76aa000 000000f8 c00109e8 [ 7.956876] bf60: d76aa000 00000000 d76abf94 d76abf78 c003a384 c00398d0 000a27f0 b6fc475c [ 7.956876] bf80: 00000000 000000f8 d76abfa4 d76abf98 c003a3d0 c003a2f8 00000000 d76abfa8 [ 7.956876] bfa0: c0010780 c003a3bc 000a27f0 b6fc475c 00000000 000a27dc ffffffff 00000000 [ 7.956876] bfc0: 000a27f0 b6fc475c 00000000 000000f8 b6fc6000 00000000 b6fc6000 00000000 [ 7.956876] bfe0: b6fee000 bede1b48 b6eb6494 b6f23964 60000010 00000000 587c1821 587c1c21 [ 7.956876] [<bf116ed4>] (nand_blk_release+0x24/0x28 [nand]) from [<bf1171c8>] (nand_release+0x2c/0x44 [nand]) [ 7.956876] [<bf1171c8>] (nand_release+0x2c/0x44 [nand]) from [<c0134da0>] (__blkdev_put+0xcc/0x164) [ 7.956876] [<c0134da0>] (__blkdev_put+0xcc/0x164) from [<c0134f5c>] (blkdev_put+0x124/0x134) [ 7.956876] [<c0134f5c>] (blkdev_put+0x124/0x134) from [<c0134f94>] (blkdev_close+0x28/0x2c) [ 7.956876] [<c0134f94>] (blkdev_close+0x28/0x2c) from [<c01045a8>] (fput+0x120/0x228) [ 7.956876] [<c01045a8>] (fput+0x120/0x228) from [<c0100dc4>] (filp_close+0x80/0x8c) [ 7.956876] [<c0100dc4>] (filp_close+0x80/0x8c) from [<c00397cc>] (put_files_struct+0xa0/0xfc) [ 7.956876] [<c00397cc>] (put_files_struct+0xa0/0xfc) from [<c00398c0>] (exit_files+0x48/0x4c) [ 7.956876] [<c00398c0>] (exit_files+0x48/0x4c) from [<c0039b80>] (do_exit+0x2bc/0x7d0) [ 7.956876] [<c0039b80>] (do_exit+0x2bc/0x7d0) from [<c003a384>] (do_group_exit+0x98/0xc4) [ 7.956876] [<c003a384>] (do_group_exit+0x98/0xc4) from [<c003a3d0>] (__wake_up_parent+0x0/0x30) [ 7.956876] [<c003a3d0>] (__wake_up_parent+0x0/0x30) from [<c0010780>] (ret_fast_syscall+0x0/0x30) [ 7.956876] Code: bad PC value [ 9.177219] ---[ end trace b1efa7b6baf6b056 ]--- [ 9.182375] Fixing recursive fault but reboot is needed!从上面的log可以看出是调用nand_blk_release函数的时候出错了，为什么会出错，pc指针的操作错误。从而证明了，即使没有主动调用close函数，系统也会在自动回收资源的时候，帮你调用close函数。
重点要说的是，调式方法：
1.先找到nand_blk_release是在哪个文件编译出来的，比如：我的是nand_blk.c
2.arm-none-linux-gnueabi-objdump -S nand_blk.o > ~/nand.S
3.分析nand.S，它是一个C语言+汇编的文件，比分析全汇编的文件方便多了。
这里就不详细分析nand.S了，因为这貌似涉及到公司秘密问题。