我将尝试解释Linux进程内存布局的基本知识,并提供以下程序作为参考:
这些内存区域的目的是什么?
然后我在运行程序后按下几次回车键。当它打印出 "Before malloc in thread 1" 后,内存布局如下:
这两个区域有什么目的?
这两个区域的目的是什么?
我正在尝试理解Linux进程内存布局的基础知识,我得到了这个程序:
#include <stdio.h> // standard io
#include <stdlib.h> // C standard library
#include <pthread.h> // threading
#include <unistd.h> // unix standard library
#include <sys/types.h> // system types for linux
// getchar basically is like "read"
// it prompts the user for input
// in this case, the input is thrown away
// which makes similar to a "pause" continuation primitive
// but a pause that is resolved through user input, which we promptly throw away!
void * thread_func (void * arg) {
printf("Before malloc in thread 1\n");
getchar();
char * addr = (char *) malloc(1000);
printf("After malloc and before free in thread 1\n");
getchar();
free(addr);
printf("After free in thread 1\n");
getchar();
}
int main () {
char * addr;
printf("Welcome to per thread arena example::%d\n", getpid());
printf("Before malloc in the main thread\n");
getchar();
addr = (char *) malloc(1000);
printf("After malloc and before free in main thread\n");
getchar();
free(addr);
printf("After free in main thread\n");
getchar();
// pointer to the thread 1
pthread_t thread_1;
// pthread_* functions return 0 upon succeeding, and other numbers upon failing
int pthread_status;
pthread_status = pthread_create(&thread_1, NULL, thread_func, NULL);
if (pthread_status != 0) {
printf("Thread creation error\n");
return -1;
}
// returned status code from thread_1
void * thread_1_status;
pthread_status = pthread_join(thread_1, &thread_1_status);
if (pthread_status != 0) {
printf("Thread join error\n");
return -1;
}
return 0;
}
当我启动程序时,/proc/<pid>/maps
中的内容如下:
00400000-00401000 r-xp 00000000 08:01 1323314 /home/oscp/xg/c/memory_layout/a.out
00600000-00601000 r--p 00000000 08:01 1323314 /home/oscp/xg/c/memory_layout/a.out
00601000-00602000 rw-p 00001000 08:01 1323314 /home/oscp/xg/c/memory_layout/a.out
7fcc372d7000-7fcc37491000 r-xp 00000000 08:01 1053757 /lib/x86_64-linux-gnu/libc-2.19.so
7fcc37491000-7fcc37691000 ---p 001ba000 08:01 1053757 /lib/x86_64-linux-gnu/libc-2.19.so
7fcc37691000-7fcc37695000 r--p 001ba000 08:01 1053757 /lib/x86_64-linux-gnu/libc-2.19.so
7fcc37695000-7fcc37697000 rw-p 001be000 08:01 1053757 /lib/x86_64-linux-gnu/libc-2.19.so
7fcc37697000-7fcc3769c000 rw-p 00000000 00:00 0
7fcc3769c000-7fcc376b5000 r-xp 00000000 08:01 1053877 /lib/x86_64-linux-gnu/libpthread-2.19.so
7fcc376b5000-7fcc378b4000 ---p 00019000 08:01 1053877 /lib/x86_64-linux-gnu/libpthread-2.19.so
7fcc378b4000-7fcc378b5000 r--p 00018000 08:01 1053877 /lib/x86_64-linux-gnu/libpthread-2.19.so
7fcc378b5000-7fcc378b6000 rw-p 00019000 08:01 1053877 /lib/x86_64-linux-gnu/libpthread-2.19.so
7fcc378b6000-7fcc378ba000 rw-p 00000000 00:00 0
7fcc378ba000-7fcc378dd000 r-xp 00000000 08:01 1053733 /lib/x86_64-linux-gnu/ld-2.19.so
7fcc37abe000-7fcc37ac1000 rw-p 00000000 00:00 0
7fcc37ad8000-7fcc37adc000 rw-p 00000000 00:00 0
7fcc37adc000-7fcc37add000 r--p 00022000 08:01 1053733 /lib/x86_64-linux-gnu/ld-2.19.so
7fcc37add000-7fcc37ade000 rw-p 00023000 08:01 1053733 /lib/x86_64-linux-gnu/ld-2.19.so
7fcc37ade000-7fcc37adf000 rw-p 00000000 00:00 0
7ffdc1cff000-7ffdc1d20000 rw-p 00000000 00:00 0 [stack]
7ffdc1dd8000-7ffdc1ddb000 r--p 00000000 00:00 0 [vvar]
7ffdc1ddb000-7ffdc1ddd000 r-xp 00000000 00:00 0 [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]
这些内存区域的目的是什么?
7fcc37491000-7fcc37691000 ---p 001ba000 08:01 1053757 /lib/x86_64-linux-gnu/libc-2.19.so
...
7fcc37abe000-7fcc37ac1000 rw-p 00000000 00:00 0
7fcc37ad8000-7fcc37adc000 rw-p 00000000 00:00 0
然后我在运行程序后按下几次回车键。当它打印出 "Before malloc in thread 1" 后,内存布局如下:
00400000-00401000 r-xp 00000000 08:01 1323314 /home/oscp/xg/c/memory_layout/a.out
00600000-00601000 r--p 00000000 08:01 1323314 /home/oscp/xg/c/memory_layout/a.out
00601000-00602000 rw-p 00001000 08:01 1323314 /home/oscp/xg/c/memory_layout/a.out
00632000-00653000 rw-p 00000000 00:00 0 [heap]
7fcc36ad6000-7fcc36ad7000 ---p 00000000 00:00 0
7fcc36ad7000-7fcc372d7000 rw-p 00000000 00:00 0
7fcc372d7000-7fcc37491000 r-xp 00000000 08:01 1053757 /lib/x86_64-linux-gnu/libc-2.19.so
7fcc37491000-7fcc37691000 ---p 001ba000 08:01 1053757 /lib/x86_64-linux-gnu/libc-2.19.so
7fcc37691000-7fcc37695000 r--p 001ba000 08:01 1053757 /lib/x86_64-linux-gnu/libc-2.19.so
7fcc37695000-7fcc37697000 rw-p 001be000 08:01 1053757 /lib/x86_64-linux-gnu/libc-2.19.so
7fcc37697000-7fcc3769c000 rw-p 00000000 00:00 0
7fcc3769c000-7fcc376b5000 r-xp 00000000 08:01 1053877 /lib/x86_64-linux-gnu/libpthread-2.19.so
7fcc376b5000-7fcc378b4000 ---p 00019000 08:01 1053877 /lib/x86_64-linux-gnu/libpthread-2.19.so
7fcc378b4000-7fcc378b5000 r--p 00018000 08:01 1053877 /lib/x86_64-linux-gnu/libpthread-2.19.so
7fcc378b5000-7fcc378b6000 rw-p 00019000 08:01 1053877 /lib/x86_64-linux-gnu/libpthread-2.19.so
7fcc378b6000-7fcc378ba000 rw-p 00000000 00:00 0
7fcc378ba000-7fcc378dd000 r-xp 00000000 08:01 1053733 /lib/x86_64-linux-gnu/ld-2.19.so
7fcc37abe000-7fcc37ac1000 rw-p 00000000 00:00 0
7fcc37ad8000-7fcc37adc000 rw-p 00000000 00:00 0
7fcc37adc000-7fcc37add000 r--p 00022000 08:01 1053733 /lib/x86_64-linux-gnu/ld-2.19.so
7fcc37add000-7fcc37ade000 rw-p 00023000 08:01 1053733 /lib/x86_64-linux-gnu/ld-2.19.so
7fcc37ade000-7fcc37adf000 rw-p 00000000 00:00 0
7ffdc1cff000-7ffdc1d20000 rw-p 00000000 00:00 0 [stack]
7ffdc1dd8000-7ffdc1ddb000 r--p 00000000 00:00 0 [vvar]
7ffdc1ddb000-7ffdc1ddd000 r-xp 00000000 00:00 0 [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]
这两个区域有什么目的?
7fcc36ad6000-7fcc36ad7000 ---p 00000000 00:00 0
7fcc36ad7000-7fcc372d7000 rw-p 00000000 00:00 0
在打印出“在线程1中进行malloc和free之后”的内容之后,它会创建另外两个区域:
7fcc30000000-7fcc30021000 rw-p 00000000 00:00 0
7fcc30021000-7fcc34000000 ---p 00000000 00:00 0
这两个区域的目的是什么?
mmap(NULL, ...)
随机选择它)。 - Peter Cordes