Messages in this thread Patch in this message | | | From | "Kirill A. Shutemov" <> | Subject | [PATCH, v3] shmat: introduce flag SHM_MAP_NOT_FIXED | Date | Tue, 7 Oct 2008 19:15:17 +0300 |
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If SHM_MAP_NOT_FIXED specified and shmaddr is not NULL, then the kernel takes shmaddr as a hint about where to place the mapping. The address of the mapping is returned as the result of the call.
It's similar to mmap() without MAP_FIXED.
Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name> Cc: Andi Kleen <andi@firstfloor.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Hugh Dickins <hugh@veritas.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Ulrich Drepper <drepper@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> --- include/linux/shm.h | 2 ++ ipc/shm.c | 7 ++++--- 2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/include/linux/shm.h b/include/linux/shm.h index eca6235..fd288eb 100644 --- a/include/linux/shm.h +++ b/include/linux/shm.h @@ -55,6 +55,8 @@ struct shmid_ds { #define SHM_RND 020000 /* round attach address to SHMLBA boundary */ #define SHM_REMAP 040000 /* take-over region on attach */ #define SHM_EXEC 0100000 /* execution access */ +#define SHM_MAP_NOT_FIXED 0200000 /* interpret attach address as a search + * hint */ /* super user shmctl commands */ #define SHM_LOCK 11 diff --git a/ipc/shm.c b/ipc/shm.c index e77ec69..54f3c61 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -819,7 +819,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr) if (shmid < 0) goto out; else if ((addr = (ulong)shmaddr)) { - if (addr & (SHMLBA-1)) { + if (!(shmflg & SHM_MAP_NOT_FIXED) && (addr & (SHMLBA-1))) { if (shmflg & SHM_RND) addr &= ~(SHMLBA-1); /* round down */ else @@ -828,7 +828,8 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr) #endif goto out; } - flags = MAP_SHARED | MAP_FIXED; + flags = MAP_SHARED | + (shmflg & SHM_MAP_NOT_FIXED ? 0 : MAP_FIXED); } else { if ((shmflg & SHM_REMAP)) goto out; @@ -892,7 +893,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr) sfd->vm_ops = NULL; down_write(¤t->mm->mmap_sem); - if (addr && !(shmflg & SHM_REMAP)) { + if (addr && !(shmflg & (SHM_REMAP|SHM_MAP_NOT_FIXED))) { err = -EINVAL; if (find_vma_intersection(current->mm, addr, addr + size)) goto invalid; -- 1.5.6.5.GIT
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