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);}