Linux 補丁生成與使用

我們在升級Linux 內核的時候，難免會接觸到補丁的知識。下麵對如何生成補丁和如何打補丁作講解。

生成補丁：

製作 hello.c 和 hello_new.c 兩個文件如如下所示。

➜  diff ls
hello.c  hello_new.c  hello_test.c  hi.patch
➜  diff cat hello.c 
#include "stdio.h"
int main(int argc ,char **argv)
{
    printf("Hello World");
}
➜  diff cat hello_new.c 
#include "stdio.h"
int main(int argc ,char **argv)
{
    printf("Hello World\n");
    return 0;
}

使用 diff  -uN 命令 進行生成patch 

➜  diff diff -uN hello_new.c hello.c > hi.patch
➜  diff cat hi.patch 
--- hello_new.c    2018-07-17 16:58:23.679704122 +0800
+++ hello.c    2018-07-17 16:57:59.190677641 +0800
@@ -1,6 +1,5 @@
 #include "stdio.h"
 int main(int argc ,char **argv)
 {
-    printf("Hello World\n");
-    return 0;
+    printf("Hello World");
 }

至此，patch 已經創建完畢。

 之後，我們進行使用 patch 命令 對 hello.c 文件進行打補丁。

➜  diff patch -p0 <hi.patch 
patching file hello.c
Reversed (or previously applied) patch detected!  Assume -R? [n] y
➜  diff cat hello.c
#include "stdio.h"
int main(int argc ,char **argv)
{
    printf("Hello World\n");
    return 0;
}
➜  diff ls
hello.c  hello.c.orig  hello_new.c  hello_test.c  hi.patch
➜  diff cat hello.c.orig 
#include "stdio.h"
int main(int argc ,char **argv)
{
    printf("Hello World");
}
➜  diff cat hello.c
#include "stdio.h"
int main(int argc ,char **argv)
{
    printf("Hello World\n");
    return 0;
}
➜  diff 

可見，補丁已經成功應用，並且生成了 .orig 源文件。 --backup-if-mismatch  選項，可以不進行生成orig 文件。

➜  diff patch -p0 --no-backup-if-mismatch < hi.patch 
patching file hello.c
Reversed (or previously applied) patch detected!  Assume -R? [n] y
➜  diff ls
hello.c  hello_new.c  hello_test.c  hi.patch
➜  diff cat hello.c 
#include "stdio.h"
int main(int argc ,char **argv)
{
    printf("Hello World\n");
    return 0;
}

diff 和 patch 命令介紹：

-pnum or --strip=num
Strip the smallest prefix containing num leading slashes from each file name found in the patch file. A sequence of one or more adjacent slashes is counted as a
single slash. This controls how file names found in the patch file are treated, in case you keep your files in a different directory than the person who sent out
the patch. For example, supposing the file name in the patch file was

/u/howard/src/blurfl/blurfl.c

setting -p0 gives the entire file name unmodified, -p1 gives

u/howard/src/blurfl/blurfl.c

without the leading slash, -p4 gives

blurfl/blurfl.c

and not specifying -p at all just gives you blurfl.c. Whatever you end up with is looked for either in the current directory, or the directory specified by the -d
option.

具體的使用說明，可以使用 man diff 和 man patch 命令來進行查看。