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| author | Sergey Bugaev <bugaevc@gmail.com> | 2023-06-26 02:17:51 +0300 |
|---|---|---|
| committer | Samuel Thibault <samuel.thibault@ens-lyon.org> | 2023-07-03 01:38:14 +0200 |
| commit | 27cb2bb93d611d772621e801bf85c8b2b4c8b598 (patch) | |
| tree | a291b70c84deb4a1719d32dffc55d7453a9f1a0c /sysdeps/mach/hurd/bits | |
| parent | 19c3b318127005444e55feb35e27d877a6af8461 (diff) | |
| download | glibc-27cb2bb93d611d772621e801bf85c8b2b4c8b598.tar.gz glibc-27cb2bb93d611d772621e801bf85c8b2b4c8b598.tar.xz glibc-27cb2bb93d611d772621e801bf85c8b2b4c8b598.zip | |
hurd: Implement MAP_EXCL
MAP_FIXED is defined to silently replace any existing mappings at the address range being mapped over. This, however, is a dangerous, and only rarely desired behavior. Various Unix systems provide replacements or additions to MAP_FIXED: * SerenityOS and Linux provide MAP_FIXED_NOREPLACE. If the address space already contains a mapping in the requested range, Linux returns EEXIST. SerenityOS returns ENOMEM, however that is a bug, as the MAP_FIXED_NOREPLACE implementation is intended to be compatible with Linux. * FreeBSD provides the MAP_EXCL flag that has to be used in combination with MAP_FIXED. It returns EINVAL if the requested range already contains existing mappings. This is directly analogous to the O_EXCL flag in the open () call. * DragonFly BSD, NetBSD, and OpenBSD provide MAP_TRYFIXED, but with different semantics. DragonFly BSD returns ENOMEM if the requested range already contains existing mappings. NetBSD does not return an error, but instead creates the mapping at a different address if the requested range contains mappings. OpenBSD behaves the same, but also notes that this is the default behavior even without MAP_TRYFIXED (which is the case on the Hurd too). Since the Hurd leans closer to the BSD side, add MAP_EXCL as the primary API to request the behavior of not replacing existing mappings. Declare MAP_FIXED_NOREPLACE and MAP_TRYFIXED as aliases of (MAP_FIXED|MAP_EXCL), so any existing software that checks for either of those macros will pick them up automatically. For compatibility with Linux, return EEXIST if a mapping already exists. Signed-off-by: Sergey Bugaev <bugaevc@gmail.com> Message-Id: <20230625231751.404120-5-bugaevc@gmail.com>
Diffstat (limited to 'sysdeps/mach/hurd/bits')
| -rw-r--r-- | sysdeps/mach/hurd/bits/mman_ext.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/sysdeps/mach/hurd/bits/mman_ext.h b/sysdeps/mach/hurd/bits/mman_ext.h index bbb94743e9..9658cdd658 100644 --- a/sysdeps/mach/hurd/bits/mman_ext.h +++ b/sysdeps/mach/hurd/bits/mman_ext.h @@ -22,5 +22,10 @@ #ifdef __USE_GNU # define SHM_ANON ((const char *) 1) -# define MAP_32BIT 0x1000 + +# define MAP_32BIT 0x1000 /* Map in the lower 2 GB. */ +# define MAP_EXCL 0x4000 /* With MAP_FIXED, don't replace existing mappings. */ + +# define MAP_TRYFIXED (MAP_FIXED | MAP_EXCL) /* BSD name. */ +# define MAP_FIXED_NOREPLACE (MAP_FIXED | MAP_EXCL) /* Linux name. */ #endif /* __USE_GNU */ |