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authorDavid Herrmann <dh.herrmann@gmail.com>2014-08-08 14:25:29 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-08-08 15:57:31 -0700
commit9183df25fe7b194563db3fec6dc3202a5855839c (patch)
tree8af760c24e1ee26e159598ae2a66912ef40cd3b0 /arch
parent40e041a2c858b3caefc757e26cb85bfceae5062b (diff)
downloadlinux-9183df25fe7b194563db3fec6dc3202a5855839c.tar.bz2
shm: add memfd_create() syscall
memfd_create() is similar to mmap(MAP_ANON), but returns a file-descriptor that you can pass to mmap(). It can support sealing and avoids any connection to user-visible mount-points. Thus, it's not subject to quotas on mounted file-systems, but can be used like malloc()'ed memory, but with a file-descriptor to it. memfd_create() returns the raw shmem file, so calls like ftruncate() can be used to modify the underlying inode. Also calls like fstat() will return proper information and mark the file as regular file. If you want sealing, you can specify MFD_ALLOW_SEALING. Otherwise, sealing is not supported (like on all other regular files). Compared to O_TMPFILE, it does not require a tmpfs mount-point and is not subject to a filesystem size limit. It is still properly accounted to memcg limits, though, and to the same overcommit or no-overcommit accounting as all user memory. Signed-off-by: David Herrmann <dh.herrmann@gmail.com> Acked-by: Hugh Dickins <hughd@google.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Ryan Lortie <desrt@desrt.ca> Cc: Lennart Poettering <lennart@poettering.net> Cc: Daniel Mack <zonque@gmail.com> Cc: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/syscalls/syscall_32.tbl1
-rw-r--r--arch/x86/syscalls/syscall_64.tbl1
2 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
index d1b4a119d4a5..028b78168d85 100644
--- a/arch/x86/syscalls/syscall_32.tbl
+++ b/arch/x86/syscalls/syscall_32.tbl
@@ -362,3 +362,4 @@
353 i386 renameat2 sys_renameat2
354 i386 seccomp sys_seccomp
355 i386 getrandom sys_getrandom
+356 i386 memfd_create sys_memfd_create
diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
index 252c804bb1aa..ca2b9aa78c81 100644
--- a/arch/x86/syscalls/syscall_64.tbl
+++ b/arch/x86/syscalls/syscall_64.tbl
@@ -325,6 +325,7 @@
316 common renameat2 sys_renameat2
317 common seccomp sys_seccomp
318 common getrandom sys_getrandom
+319 common memfd_create sys_memfd_create
#
# x32-specific system call numbers start at 512 to avoid cache impact