I have allocated code using mmap, but unable to free it because of segmentation fault. I have done mprotect - PROT_WRITE to make it writable, but still i am unable to free it.
我已经使用mmap分配了代码,但由于分段错误而无法释放代码。我已经完成了mprotect - PROT_WRITE以使其可写,但我仍然无法释放它。
Please help me.
请帮我。
enter code here
1 #include <stdio.h>
2 #include <memory.h>
3 #include <stdlib.h>
4 #include <unistd.h>
5 #include <sys/mman.h>
6 #include <sys/types.h>
7 #include <fcntl.h>
8
9 int main()
10 {
11 void * allocation;
12 size_t size;
13 static int devZerofd = -1;
14
15 if ( devZerofd == -1 ) {
16 devZerofd = open("/dev/zero", O_RDWR);
17 if ( devZerofd < 0 )
18 perror("open() on /dev/zero failed");
19 }
20
21 allocation = (caddr_t) mmap(0, 5000, PROT_READ|PROT_NONE, MAP_PRIVATE, devZerofd, 0);
22
23 if ( allocation == (caddr_t)-1 )
24 fprintf(stderr, "mmap() failed ");
25
26 if ( mprotect((caddr_t)allocation, 5000, PROT_WRITE) < 0 )
27 fprintf(stderr, "mprotect failed");
28 else
29 printf("mprotect done: memory allocated at address %u\n",allocation);
30
31 strcpy(allocation,"Hello, how are you");
32 puts(allocation);
33
34 if ( mprotect((caddr_t)allocation, 5000, PROT_WRITE) < 0 )
35 fprintf(stderr, "mprotect failed");
36
37 free(allocation);
38
39 }
40
41
1 个解决方案
#1
15
You need to use munmap for that. You don't need to do anything else (change protection bits etc). But you should check the return code of munmap.
你需要使用munmap。您不需要做任何其他事情(更改保护位等)。但你应该检查munmap的返回码。
munmap(allocation, 5000);
free(3) can only be used to free memory allocated via malloc(3).
free(3)只能用于释放通过malloc(3)分配的内存。
#1
15
You need to use munmap for that. You don't need to do anything else (change protection bits etc). But you should check the return code of munmap.
你需要使用munmap。您不需要做任何其他事情(更改保护位等)。但你应该检查munmap的返回码。
munmap(allocation, 5000);
free(3) can only be used to free memory allocated via malloc(3).
free(3)只能用于释放通过malloc(3)分配的内存。