Re: [PATCH vm-limit v2] Remaining patches of the VM limit implementation

[Diego Nieto Cid]

On Mon, Sep 01, 2025 at 12:18:51AM +0200, Samuel Thibault wrote:
> 
> I'm thinking that probably the __vm_set_size_limit call, since it is
> directed to the host port, does not actually go through rpctrace

Ok

> Do you actually see the RPC call?

No, there's no entry for the vm_set_size_limit in the rpctrace
output when I use the setrlimit function.

But, with the atttached program (which calls vm_set_size_limit directly)
it is shown correctly in rpctrace:

    ...
    38<--44(pid3837)->proc_getprivports_request () = 0    60<--55(pid3837)    
31<--62(pid3837) 
    task9(pid3837)->mach_port_mod_refs (pn{ 20} 0 1) = 0
    49<--25(pid3837)->io_write_request ("task=0x1; host=0x14\n" -1)task=0x1; 
host=0x14
     = 0 20
    60<--55(pid3837)->vm_set_size_limit ( task9(pid3837) 2147483648 2147483648) 
= 0
    task9(pid3837)->mach_port_deallocate (pn{ 20}) = 0
    38<--44(pid3837)->proc_mark_exit_request (0 0) = 0
    task9(pid3837)->task_terminate () = 0

That lead me to suspect of the GLIBC implementation (or the installation).
Just in case, I will try again after addressing the review of the gnumach part.


Regards,
Diego

#include <error.h>
#include <hurd.h>
#include <mach/mach.h>
#include <mach/gnumach.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>

static const size_t M_2GB = 2l * 1024l * 1024l * 1024l;

int main (int argc, char **argv)
{
  kern_return_t err;
  mach_port_t task = mach_task_self ();
  mach_port_t host = MACH_PORT_NULL;

  err = get_privileged_ports (&host, NULL);
  if (err)
    error (1, err, "error getting host priv port");

  fprintf (stderr, "task=0x%x; host=0x%x\n", task, host);

  err = vm_set_size_limit(host, task, M_2GB, M_2GB);

  if (host != MACH_PORT_NULL)
    mach_port_deallocate (task, host);

  if (err)
    error (1, err, "error setting size limit task");

  return 0;
}