kernel hexdump分析

驱动调试中,很多时候是二进制的，这个时候hexdump就是个非常有用的工具了。
不要再自己去实现类似的功能，kernel代码里面就有：
参考： kernel/lib/hexdump.c
// 0Xxx转换成 ASCII ,实现简单巧妙

const char hex_asc[] = "0123456789abcdef";

#define hex_asc_lo(x)	hex_asc[((x) & 0x0f)]

#define hex_asc_hi(x)	hex_asc[((x) & 0xf0) >> 4]

void hex_dump_to_buffer(const void *buf, size_t len, int rowsize,

			int groupsize, char *linebuf, size_t linebuflen,

			bool ascii)

{

	const u8 *ptr = buf;

	u8 ch;

	int j, lx = 0;

	int ascii_column;

        // 每行固定16或者32个字节，符合国际审美观

	if (rowsize != 16 && rowsize != 32)

		rowsize = 16;

	if (!len)

		goto nil;

	if (len > rowsize)		/* limit to one line at a time */

		len = rowsize;

	if ((len % groupsize) != 0)	/* no mixed size output */

		groupsize = 1;

	switch (groupsize) {

	......

	default:

                //  转换成ASCii 形式

		for (j = 0; (j < len) && (lx + 3) <= linebuflen; j++) {

			ch = ptr[j];

			linebuf[lx++] = hex_asc_hi(ch);

			linebuf[lx++] = hex_asc_lo(ch);

			linebuf[lx++] = ' ';

		}

		if (j)

			lx--;

		ascii_column = 3 * rowsize + 2;

		break;

	}

	if (!ascii)

		goto nil;

        // 加上对应的ASCII字符串，区别如下：

        //  0009ab42: 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f  @ABCDEFGHIJKLMNO

        //  0009ab42: 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f

	while (lx < (linebuflen - 1) && lx < (ascii_column - 1))

		linebuf[lx++] = ' ';

	for (j = 0; (j < len) && (lx + 2) < linebuflen; j++) {

		ch = ptr[j];

		linebuf[lx++] = (isascii(ch) && isprint(ch)) ? ch : '.';

	}

nil:

        // 记得加上结束符号，有可能导致printk --> kernel panic

	linebuf[lx++] = '\0';

}

void print_hex_dump(const char *level, const char *prefix_str, int prefix_type,

		    int rowsize, int groupsize,

		    const void *buf, size_t len, bool ascii)

{

	const u8 *ptr = buf;

	int i, linelen, remaining = len;

        /* 每行数据类似下面

           40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f  @ABCDEFGHIJKLMNO

           |                                          |  |                 |

           -----------------------------------------------

                    16*3 or 32*3                       2      32+1

        */

	unsigned char linebuf[32 * 3 + 2 + 32 + 1];

	if (rowsize != 16 && rowsize != 32)

		rowsize = 16;

	for (i = 0; i < len; i += rowsize) {

		linelen = min(remaining, rowsize);

		remaining -= rowsize;

                //  linebuf 返回需要打印的字符串

		hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,

				   linebuf, sizeof(linebuf), ascii);

                // 是否使用前缀

		switch (prefix_type) {

                     // 加上绝对地址

		case DUMP_PREFIX_ADDRESS:

			printk("%s%s%p: %s\n",

			       level, prefix_str, ptr + i, linebuf);

			break;

                     // 只是简单地加上偏移量而已

		case DUMP_PREFIX_OFFSET:

			printk("%s%s%.8x: %s\n", level, prefix_str, i, linebuf);

			break;

		default:

			printk("%s%s%s\n", level, prefix_str, linebuf);

			break;

		}

	}

}

// 一般在kernel代码中，调用此接口，许多参数用默认的，不需要了解太多细节

void print_hex_dump_bytes(const char *prefix_str, int prefix_type,

			  const void *buf, size_t len)

{

	print_hex_dump(KERN_DEBUG, prefix_str, prefix_type, 16, 1,

		       buf, len, true);

}