Linux 如何释放使用 mmap 分配的内存？
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How to free memory allocated using mmap?
提问by kingsmasher1
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它。我已经完成了 mprotect - PROT_WRITE 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
采纳答案by cnicutar
You need to use munmapfor 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它。您不需要做任何其他事情（更改保护位等）。但是您应该检查munmap.
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).
