Re: [PATCH v2 0/3] gnumach VM entry re-coalescing

[Samuel Thibault]

Hello,

Sorry for the delay, I could test this more than just booting, and
confirm that this fixes the numerous map entries for successive mallocs
in processes :)

Applied, thanks!
Samuel

Sergey Bugaev, le mer. 05 juil. 2023 17:16:36 +0300, a ecrit:
> This is the remaining patches from "Forward merging entries and other
> VM shenanigans" (specifically the vm_map_coalesce_entry part), with
> that one issue fixed. And here's a reproducer that fails with v1 and
> works now:
> 
> Sergey
> 
> 
> #define _GNU_SOURCE
> 
> #include <stdio.h>
> #include <mach.h>
> #include <error.h>
> #include <errno.h>
> #include <unistd.h>
> #include <spawn.h>
> #include <sys/wait.h>
> 
> int
> main ()
> {
>   error_t err;
>   vm_offset_t offset;
>   extern char **environ;
>   pid_t pid;
>   int *ptr;
>   char *child_argv[] = { "vminfo", NULL, NULL };
> 
>   asprintf (&child_argv[1], "%d", getpid ());
> 
>   /* Allocate space for four pages.  */
>   err = vm_allocate (mach_task_self (), &offset, vm_page_size * 4, 1);
>   if (err)
>     error (1, err, "vm_allocate space");
> 
>   printf ("Allocated at %p\n", (void *) (offset + vm_page_size));
> 
>   /* Deallocate them back!  */
>   err = vm_deallocate (mach_task_self (), offset, vm_page_size * 4);
>   if (err)
>     error (1, err, "vm_deallocate space");
> 
>   offset += vm_page_size;
> 
>   /* Allocate the two pages.  */
>   err = vm_allocate (mach_task_self (), &offset, vm_page_size * 2, 0);
>   if (err)
>     error (1, err, "vm_allocate");
> 
>   ptr = (int *) (offset + vm_page_size);
> 
>   /* Realize the object.  */
>   *ptr = 1234;
> 
>   /* Deallocate the first page, and reallocate it
>      with a different protection.  */
>   err = vm_deallocate (mach_task_self (), offset, vm_page_size);
>   if (err)
>     error (1, err, "vm_deallocate page");
> 
>   err = vm_map (mach_task_self (), &offset, vm_page_size, 0, 0,
>                 MACH_PORT_NULL, 0, 0, VM_PROT_ALL, VM_PROT_ALL,
>                 VM_INHERIT_COPY);
>   if (err)
>     error (1, err, "vm_map");
> 
>   printf ("====== Before coalescing ======\n");
>   fflush (stdout);
>   posix_spawn (&pid, "/bin/vminfo", NULL, NULL, child_argv, environ);
>   wait (NULL);
> 
>   /* Coalesce the two entries back together.  */
>   err = vm_protect (mach_task_self (), offset,
>                     vm_page_size, 0, VM_PROT_DEFAULT);
>   if (err)
>     error (1, err, "vm_protect (VM_PROT_DEFAULT)");
> 
>   printf ("====== After coalescing ======\n");
>   fflush (stdout);
>   posix_spawn (&pid, "/bin/vminfo", NULL, NULL, child_argv, environ);
>   wait (NULL);
> 
>   /* Check whether the data is still there.  */
>   printf ("%d\n", *(const int *) (offset + vm_page_size));
> }
> 

-- 
Samuel
---
Pour une évaluation indépendante, transparente et rigoureuse !
Je soutiens la Commission d'Évaluation de l'Inria.