处理不受setrlimit限制的资源

Question

我写了一个简单的程序来限制它的数据大小为65Kb,并验证相同我分配一个超过65Kb的虚拟内存,逻辑上如果我正在做所有正确(如下)malloc调用应该失败,不是吗？

#include <sys/resource.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>

int main (int argc, char *argv[])
{
  struct rlimit limit;


  /* Get max data size . */
  if (getrlimit(RLIMIT_DATA, &limit) != 0) {
    printf("getrlimit() failed with errno=%d\n", errno);
    return 1;
  }

  printf("The soft limit is %lu\n", limit.rlim_cur);
  printf("The hard limit is %lu\n", limit.rlim_max);

  limit.rlim_cur = 65 * 1024;
  limit.rlim_max = 65 * 1024;

  if (setrlimit(RLIMIT_DATA, &limit) != 0) {
    printf("setrlimit() failed with errno=%d\n", errno);
    return 1;
  }

  if (getrlimit(RLIMIT_DATA, &limit) != 0) {
    printf("getrlimit() failed with errno=%d\n", errno);
    return 1;
  }

  printf("The soft limit is %lu\n", limit.rlim_cur);
  printf("The hard limit is %lu\n", limit.rlim_max);
  system("bash -c 'ulimit -a'");
    int *new2 = NULL;
    new2 = malloc(66666666);
    if (new2 == NULL)
    {
        printf("malloc failed\n");
        return;
    }
    else
    {
        printf("success\n");
    }

  return 0;
}

令人惊讶的是,输出是这样的 -

The soft limit is 4294967295
The hard limit is 4294967295
The soft limit is 66560
The hard limit is 66560
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) 65
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 14895
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 14895
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
success

我做错了吗？请放弃您的输入.谢谢!

Answer 1

从setrlimit手册页:

RLIMIT_DATA

进程数据段的最大大小(初始化数据,未初始化数据和堆).此限制会影响对brk(2)和sbrk(2)的调用,这些调用在遇到此资源的软限制时会因错误ENOMEM而失败.

具体而言,该资源不适用于通过获取的内存mmap.内部malloc使用各种机制来获取新内存.在这种情况下,你会发现它使用mmap而不是sbrk或brk.您可以通过从程序中转储系统调用来验证这一点strace.

要实现您想要的功能,请使用RLIMIT_AS资源.