如何使用strsep（）来象征字符串
我有一个内核模块，在模块中，我正在尝试使用strep（）拆分字符串。我有以下解密变量，其中包含我要拆分的字符串。
unsigned char decrypt[KEY_SIZE];
printk(KERN_DEBUG "%s\n", decrypt);
输出：
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
E = 010001
D = 21AFE07431CE47269083F8F8B7ABCBCEDA6DCB975457BE6662942C64091586FEE755C9A3832EAA0868665DB507A41A15F1EDF12E44ECF03D0E61111D457D730FA700D0FB0B6C13607C0F5F1DDDEB61AE9019E53A9C998F2AD5924430EEA3E9DA1B0E5F2B575DDBE86C4096B5C87661F7A7E7F7F21D0701509BBA881B4AE463F6F18C7F04AB742319E2D7319EECA136EEB0CF7B2BFA87E3A0E69FBC0E5FDC7EE6271EB2CA09DDBF7C8B57D951762708D76890E62858C1D5FC5B7E40D50913CE7797BD80F6A398FB92703FBDD33FBCB129B86E54F13EC14DA68BE139634DD1E9C01F01751
...
...
我正在使用以下代码提取值。我的目标是获取n，e，d的值。当我调用此模块时，我的机器冻结了。但是，当我使用gdb调试循环时，它会起作用。
正如@john Bollinger所问的那样，我有以下行可以在使用strsep（）之前进行字符串null终止。
size_t lenght = strlen(decrypt);
int N = lenght - 2361; // 2361 is the original size
decrypt[lenght - N] = '\0';
代码：
char *s3 = decrypt;
int k = 0;
int size = 0;
char *test;
while (s3 != NULL) {
test = strsep(&s3, " ");
test = strsep(&s3, " ");
test = strsep(&s3, "\n");
switch (k) {
case 0:
size = strlen(test);
printk(KERN_DEBUG "token id %d: size %d, token is %s\n", k, size, test);
break;
case 1:
size = strlen(test);
printk(KERN_DEBUG "token id %d: size %d, token is %s\n", k, size, test);
break;
case 2:
size = strlen(test);
printk(KERN_DEBUG "token id %d: size %d, token is %s\n", k, size, test);
break;
........
........
}
k = k + 1;
}
有人可以告诉我，我在这里做什么？还是有其他线程安全功能可以拆分字符串？提前致谢。
内核版本：Linux 4.15.0-142代
I have a kernel module, and in the module, I'm trying to split a string using strsep(). I have the following decrypt variable that contains the string I'm trying to split.
unsigned char decrypt[KEY_SIZE];
printk(KERN_DEBUG "%s\n", decrypt);
output:
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
E = 010001
D = 21AFE07431CE47269083F8F8B7ABCBCEDA6DCB975457BE6662942C64091586FEE755C9A3832EAA0868665DB507A41A15F1EDF12E44ECF03D0E61111D457D730FA700D0FB0B6C13607C0F5F1DDDEB61AE9019E53A9C998F2AD5924430EEA3E9DA1B0E5F2B575DDBE86C4096B5C87661F7A7E7F7F21D0701509BBA881B4AE463F6F18C7F04AB742319E2D7319EECA136EEB0CF7B2BFA87E3A0E69FBC0E5FDC7EE6271EB2CA09DDBF7C8B57D951762708D76890E62858C1D5FC5B7E40D50913CE7797BD80F6A398FB92703FBDD33FBCB129B86E54F13EC14DA68BE139634DD1E9C01F01751
...
...
I'm using the following code to extract the values. My goal is to get the value of N, E, D in each case. When I call this module, my machine freeze. However, when I use gdb to debug the loop, it works.
As @John Bollinger asked, I have the following line to make the string null-terminated before using strsep().
size_t lenght = strlen(decrypt);
int N = lenght - 2361; // 2361 is the original size
decrypt[lenght - N] = '\0';
Code:
char *s3 = decrypt;
int k = 0;
int size = 0;
char *test;
while (s3 != NULL) {
test = strsep(&s3, " ");
test = strsep(&s3, " ");
test = strsep(&s3, "\n");
switch (k) {
case 0:
size = strlen(test);
printk(KERN_DEBUG "token id %d: size %d, token is %s\n", k, size, test);
break;
case 1:
size = strlen(test);
printk(KERN_DEBUG "token id %d: size %d, token is %s\n", k, size, test);
break;
case 2:
size = strlen(test);
printk(KERN_DEBUG "token id %d: size %d, token is %s\n", k, size, test);
break;
........
........
}
k = k + 1;
}
Can someone please tell me, what am I doing incorrectly here? Or is there any other thread-safe function available to split a string? Thanks in advance.
Kernel version: Linux 4.15.0-142-generic
如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱，如果其他用户或者作者回复了您的评论，将不能在第一时间通知您！
发布评论
评论（1）
我看到您显然在使用结果之前没有验证结果之前的一件事。如果输入恰好不完全按照您的预期进行格式，那么
test在输入到switch> switch时很容易成为，并且该代码似乎没有预期这种可能性。当然，“不完全按照您的期望，格式化”也可能意味着有错误的期望。例如，触发上述
test的NULL值的一种方法是输入的最后一行，以新线结束。在这种情况下，strsep不会注意到它已经到达字符串的末端，直到下一个周期。另外，此声明是可疑的：
如果数据可以达到
key_size的长度，则没有为字符串终止器留出空间。如果要通过strsep（）将其作为字符串处理，或者通过printk将其输出或将其输出为字符串，则必须具有字符串终结器。如果数据自然没有终结器，则需要确保添加一个（必须离开空间）。此外，除最后一个令牌外，本身本身并非错误 。您可以通过简单的指针差来获得彼此代币的长度：
s3 -test -1。The one thing I see that you are clearly doing wrong is not validating your results before using them. If the input happens not to be formatted exactly as you expect, then it is easily possible for
testto be null at entry to theswitch, and the code does not appear to anticipate that possibility.Of course, "not formatted exactly as you expect" might also mean having the wrong expectations. For example, one way to trigger the aforementioned null value of
testwould be for the last line of the input to end with a newline. In that case,strsepwould not notice that it had reached the end of the string until the next cycle.Also, this declaration is suspicious:
If the data can be up to
KEY_SIZEin length, then that leaves no room for a string terminator. You must have a string terminator if you are processing it as a string viastrsep()or outputting it or a tail of it as a string viaprintk. If the data don't naturally have a terminator then you need to make sure to add one (for which you must leave space).Additionally, not wrong per se, but wasteful: calling
strlen(), except for the last token. You can get the length of each other token by simple pointer difference:s3 - test - 1.