Messages in this thread | | | Date | Wed, 8 Oct 2008 10:57:21 +0200 | From | "Michael Kerrisk" <> | Subject | Re: [PATCH, v3] shmat: introduce flag SHM_MAP_NOT_FIXED |
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Kirill,
On Tue, Oct 7, 2008 at 6:15 PM, Kirill A. Shutemov <kirill@shutemov.name> wrote: > 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.
Please CC linux-api@vger.kernel.org on patches that change the kernel-userspace interface.
Cheers,
Michael
> 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 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
-- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Found a documentation bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html
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