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From: Samuel Thibault <sthibaul@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc] hurd: Implement SHM_ANON Date: Wed, 1 Feb 2023 22:36:33 +0000 (GMT) [thread overview] Message-ID: <20230201223633.D2E793858CDA@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=a979b72747e34add3433a23c0966490cd809120f commit a979b72747e34add3433a23c0966490cd809120f Author: Sergey Bugaev <bugaevc@gmail.com> Date: Mon Jan 30 15:52:16 2023 +0300 hurd: Implement SHM_ANON 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> Message-Id: <20230130125216.6254-4-bugaevc@gmail.com> Diff: --- 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(-) diff --git a/posix/shm-directory.c b/posix/shm-directory.c index 47e2355d0d..86d9fd8e4f 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 48970bbc81..6c1f4d604f 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 0000000000..f022826eee --- /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 */
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