Re: [PATCH 1/4] hurd: Implement MAP_32BIT

[Samuel Thibault]

Applied, thanks!

Sergey Bugaev, le lun. 24 avril 2023 00:55:23 +0300, a ecrit:
> This is a flag that can be passed to mmap () to request that the mapping
> being established should be located in the lower 2 GB area of the
> address space, so only the lower 31 (not 32) bits can be set in its
> address, and the address can be represented as a 32-bit integer without
> truncating it.
> 
> This flag is intended to be compatible with Linux, FreeBSD, and Darwin
> flags of the same name. Out of those systems, it appears Linux and
> FreeBSD take MAP_32BIT to mean "map 31 bit", whereas Darwin allows the
> 32nd bit to be set in the address as well. The Hurd follows Linux and
> FreeBSD behavior.
> 
> Unlike on those systems, on the Hurd MAP_32BIT is defined on all
> supported architectures (which currently are only i386 and x86_64).
> 
> Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
> ---
>  sysdeps/mach/hurd/bits/mman_ext.h |  1 +
>  sysdeps/mach/hurd/dl-sysdep.c     |  8 +++++---
>  sysdeps/mach/hurd/mmap.c          | 10 ++++++----
>  3 files changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/sysdeps/mach/hurd/bits/mman_ext.h 
> b/sysdeps/mach/hurd/bits/mman_ext.h
> index f022826e..bbb94743 100644
> --- a/sysdeps/mach/hurd/bits/mman_ext.h
> +++ b/sysdeps/mach/hurd/bits/mman_ext.h
> @@ -22,4 +22,5 @@
>  
>  #ifdef __USE_GNU
>  # define SHM_ANON    ((const char *) 1)
> +# define MAP_32BIT   0x1000
>  #endif /* __USE_GNU  */
> diff --git a/sysdeps/mach/hurd/dl-sysdep.c b/sysdeps/mach/hurd/dl-sysdep.c
> index 6e167e12..d7b309e0 100644
> --- a/sysdeps/mach/hurd/dl-sysdep.c
> +++ b/sysdeps/mach/hurd/dl-sysdep.c
> @@ -451,7 +451,7 @@ __mmap (void *addr, size_t len, int prot, int flags, int 
> fd, off_t offset)
>  {
>    error_t err;
>    vm_prot_t vmprot;
> -  vm_address_t mapaddr;
> +  vm_address_t mapaddr, mask;
>    mach_port_t memobj_rd, memobj_wr;
>  
>    vmprot = VM_PROT_NONE;
> @@ -462,6 +462,8 @@ __mmap (void *addr, size_t len, int prot, int flags, int 
> fd, off_t offset)
>    if (prot & PROT_EXEC)
>      vmprot |= VM_PROT_EXECUTE;
>  
> +  mask = (flags & MAP_32BIT) ? ~(vm_address_t) 0x7FFFFFFF : 0;
> +
>    if (flags & MAP_ANON)
>      memobj_rd = MACH_PORT_NULL;
>    else
> @@ -476,7 +478,7 @@ __mmap (void *addr, size_t len, int prot, int flags, int 
> fd, off_t offset)
>  
>    mapaddr = (vm_address_t) addr;
>    err = __vm_map (__mach_task_self (),
> -               &mapaddr, (vm_size_t) len, 0,
> +               &mapaddr, (vm_size_t) len, mask,
>                 !(flags & MAP_FIXED),
>                 memobj_rd,
>                 (vm_offset_t) offset,
> @@ -491,7 +493,7 @@ __mmap (void *addr, size_t len, int prot, int flags, int 
> fd, off_t offset)
>        if (! err)
>       err = __vm_map (__mach_task_self (),
>                       &mapaddr, (vm_size_t) len,
> -                     0,
> +                     mask,
>                       !(flags & MAP_FIXED),
>                       memobj_rd, (vm_offset_t) offset,
>                       flags & (MAP_COPY|MAP_PRIVATE),
> diff --git a/sysdeps/mach/hurd/mmap.c b/sysdeps/mach/hurd/mmap.c
> index 20a41e36..c3cc1856 100644
> --- a/sysdeps/mach/hurd/mmap.c
> +++ b/sysdeps/mach/hurd/mmap.c
> @@ -36,7 +36,7 @@ __mmap (void *addr, size_t len, int prot, int flags, int 
> fd, off_t offset)
>    error_t err;
>    vm_prot_t vmprot, max_vmprot;
>    memory_object_t memobj;
> -  vm_address_t mapaddr;
> +  vm_address_t mapaddr, mask;
>    boolean_t copy;
>  
>    mapaddr = (vm_address_t) addr;
> @@ -55,6 +55,8 @@ __mmap (void *addr, size_t len, int prot, int flags, int 
> fd, off_t offset)
>  
>    copy = ! (flags & MAP_SHARED);
>  
> +  mask = (flags & MAP_32BIT) ? ~(vm_address_t) 0x7FFFFFFF : 0;
> +
>    switch (flags & MAP_TYPE)
>      {
>      default:
> @@ -134,7 +136,7 @@ __mmap (void *addr, size_t len, int prot, int flags, int 
> fd, off_t offset)
>      max_vmprot = VM_PROT_ALL;
>  
>    err = __vm_map (__mach_task_self (),
> -               &mapaddr, (vm_size_t) len, (vm_address_t) 0,
> +               &mapaddr, (vm_size_t) len, mask,
>                 mapaddr == 0,
>                 memobj, (vm_offset_t) offset,
>                 copy, vmprot, max_vmprot,
> @@ -149,7 +151,7 @@ __mmap (void *addr, size_t len, int prot, int flags, int 
> fd, off_t offset)
>         err = __vm_deallocate (__mach_task_self (), mapaddr, len);
>         if (! err)
>           err = __vm_map (__mach_task_self (),
> -                         &mapaddr, (vm_size_t) len, (vm_address_t) 0,
> +                         &mapaddr, (vm_size_t) len, mask,
>                           0, memobj, (vm_offset_t) offset,
>                           copy, vmprot, max_vmprot,
>                           copy ? VM_INHERIT_COPY : VM_INHERIT_SHARE);
> @@ -159,7 +161,7 @@ __mmap (void *addr, size_t len, int prot, int flags, int 
> fd, off_t offset)
>      {
>        if (mapaddr != 0 && (err == KERN_NO_SPACE || err == 
> KERN_INVALID_ADDRESS))
>       err = __vm_map (__mach_task_self (),
> -                     &mapaddr, (vm_size_t) len, (vm_address_t) 0,
> +                     &mapaddr, (vm_size_t) len, mask,
>                       1, memobj, (vm_offset_t) offset,
>                       copy, vmprot, max_vmprot,
>                       copy ? VM_INHERIT_COPY : VM_INHERIT_SHARE);
> -- 
> 2.40.0
> 

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