Hi,
I've been testing RLIMIT_DATA...
On Thu, Dec 19, 2024 at 10:36:49PM +0100, Luca wrote:
>
> I see that some limits (e.g. RLIMIT_DATA) are managed in glibc instead of
> gnumach, maybe this could be a simpler way to add some minimal support? I
> guess that one might overcome these limits by using directly the mach rpc or
> hijacking glibc, but it could be enough for some use cases.
>
I failed to make it do anything. The only place where RLIMIT_DATA is read is
in the Mach/Hurd specific `__hurd_set_brk` function.
glibc-2.40/sysdeps/mach/hurd/brk.c: rlimit =
_hurd_rlimits[RLIMIT_DATA].rlim_cur;
[line 92]
Which is called from __sbrk, and at that point I'm lost.
Also, I cannot make it to fail with the attached test program.
#include <errno.h>
#include <error.h>
#include <limits.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/resource.h>
#include <unistd.h>
static const size_t M_1GB = (size_t) 1 * (size_t) 1024 * (size_t) 1024 * (size_t) 1024;
static const size_t M_2GB = (size_t) 2 * M_1GB;
static const size_t M_4GB = (size_t) 4 * M_1GB;
static const size_t M_8GB = (size_t) 8 * M_1GB;
int
main(int argc, char **argv)
{
if (argc > 1 && argv[1][0] == 'l')
{
struct rlimit lims = { M_1GB / 4, M_1GB / 4 };
int err = setrlimit(RLIMIT_DATA, &lims);
if (err == -1)
{
error(1, errno, "setrlimit failed");
}
}
void *addr1 = malloc(M_8GB);
if (addr1 == NULL)
{
error(1, errno, "[addr1] mmap failed: errno=%u, ", errno);
}
void *addr2 = malloc(M_8GB);
if (addr2 == NULL)
{
free(addr1);
error(1, errno, "[addr2] mmap failed");
}
free(addr1);
free(addr2);
return 0;
}
