Re: [PATCH v2 3/3] hurd: Implement SHM_ANON

[Samuel Thibault]

Applied, thanks!

Sergey Bugaev, le lun. 30 janv. 2023 15:52:16 +0300, a ecrit:
> This adds a special SHM_ANON value that can be passed into shm_open ()
> in place of a name. When called in this way, shm_open () will create a
> new anonymous shared memory file. The file will be created in the same
> way that other shared memory files are created (i.e., under /dev/shm/),
> except that it is not given a name and therefore cannot be reached from
> the file system, nor by other calls to shm_open (). This is accomplished
> by utilizing O_TMPFILE.
> 
> This is intended to be compatible with FreeBSD's API of the same name.
> 
> Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
> ---
>  posix/shm-directory.c             | 25 +++++++++++++++++++++----
>  rt/shm_open.c                     |  5 +++++
>  sysdeps/mach/hurd/bits/mman_ext.h | 25 +++++++++++++++++++++++++
>  3 files changed, 51 insertions(+), 4 deletions(-)
>  create mode 100644 sysdeps/mach/hurd/bits/mman_ext.h
> 
> diff --git a/posix/shm-directory.c b/posix/shm-directory.c
> index 47e2355d..86d9fd8e 100644
> --- a/posix/shm-directory.c
> +++ b/posix/shm-directory.c
> @@ -23,17 +23,34 @@
>  #include <alloc_buffer.h>
>  #include <shm-directory.h>
>  #include <string.h>
> +#include <sys/mman.h>
> +#include <fcntl.h>
>  
>  int
>  __shm_get_name (struct shmdir_name *result, const char *name, bool 
> sem_prefix)
>  {
> +  struct alloc_buffer buffer;
> +  size_t namelen;
> +
> +  buffer = alloc_buffer_create (result->name, sizeof (result->name));
> +  alloc_buffer_copy_bytes (&buffer, SHMDIR, strlen (SHMDIR));
> +
> +#if defined (SHM_ANON) && defined (O_TMPFILE)
> +  if (name == SHM_ANON)
> +    {
> +      /* For SHM_ANON, we want shm_open () to pass O_TMPFILE to open (),
> +         with SHMDIR itself as the path.  So, leave it at that.  */
> +      alloc_buffer_add_byte (&buffer, 0);
> +      if (alloc_buffer_has_failed (&buffer))
> +        return -1;
> +      return 0;
> +    }
> +#endif
> +
>    while (name[0] == '/')
>      ++name;
> -  size_t namelen = strlen (name);
> +  namelen = strlen (name);
>  
> -  struct alloc_buffer buffer
> -    = alloc_buffer_create (result->name, sizeof (result->name));
> -  alloc_buffer_copy_bytes (&buffer, SHMDIR, strlen (SHMDIR));
>    if (sem_prefix)
>      alloc_buffer_copy_bytes (&buffer, "sem.", strlen ("sem."));
>    alloc_buffer_copy_bytes (&buffer, name, namelen + 1);
> diff --git a/rt/shm_open.c b/rt/shm_open.c
> index 48970bbc..6c1f4d60 100644
> --- a/rt/shm_open.c
> +++ b/rt/shm_open.c
> @@ -23,6 +23,7 @@
>  #include <shlib-compat.h>
>  #include <shm-directory.h>
>  #include <unistd.h>
> +#include <sys/mman.h>
>  
>  /* Open shared memory object.  */
>  int
> @@ -36,6 +37,10 @@ __shm_open (const char *name, int oflag, mode_t mode)
>      }
>  
>    oflag |= O_NOFOLLOW | O_CLOEXEC;
> +#if defined (SHM_ANON) && defined (O_TMPFILE)
> +  if (name == SHM_ANON)
> +    oflag |= O_TMPFILE;
> +#endif
>  
>    int fd = __open64_nocancel (dirname.name, oflag, mode);
>    if (fd == -1 && __glibc_unlikely (errno == EISDIR))
> diff --git a/sysdeps/mach/hurd/bits/mman_ext.h 
> b/sysdeps/mach/hurd/bits/mman_ext.h
> new file mode 100644
> index 00000000..f022826e
> --- /dev/null
> +++ b/sysdeps/mach/hurd/bits/mman_ext.h
> @@ -0,0 +1,25 @@
> +/* System-specific extensions of <sys/mman.h>, Hurd version.
> +   Copyright (C) 2022 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#ifndef _SYS_MMAN_H
> +# error "Never include <bits/mman_ext.h> directly; use <sys/mman.h> instead."
> +#endif
> +
> +#ifdef __USE_GNU
> +# define SHM_ANON    ((const char *) 1)
> +#endif /* __USE_GNU  */
> -- 
> 2.39.1
> 

-- 
Samuel
---
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