From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60931) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZgwLV-0005S8-Di for qemu-devel@nongnu.org; Tue, 29 Sep 2015 10:57:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZgwLP-0007tb-JJ for qemu-devel@nongnu.org; Tue, 29 Sep 2015 10:57:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56037) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZgwLP-0007tT-BC for qemu-devel@nongnu.org; Tue, 29 Sep 2015 10:57:27 -0400 Date: Tue, 29 Sep 2015 17:57:22 +0300 From: "Michael S. Tsirkin" Message-ID: <20150929174638-mutt-send-email-mst@redhat.com> References: <1438864852-4939-1-git-send-email-marcandre.lureau@redhat.com> <1438864852-4939-4-git-send-email-marcandre.lureau@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1438864852-4939-4-git-send-email-marcandre.lureau@redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v3 03/16] util: add memfd helpers List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: marcandre.lureau@redhat.com Cc: haifeng.lin@huawei.com, thibaut.collet@6wind.com, jasowang@redhat.com, qemu-devel@nongnu.org, pbonzini@redhat.com On Thu, Aug 06, 2015 at 02:40:39PM +0200, marcandre.lureau@redhat.com wro= te: > From: Marc-Andr=E9 Lureau >=20 > Add qemu_memfd_alloc/free() helpers. >=20 > The function helps to allocate and seal a memfd, and implements an > open/unlink/mmap fallback for system that do not support memfd. >=20 > Signed-off-by: Marc-Andr=E9 Lureau > --- > include/qemu/memfd.h | 4 +++ > util/memfd.c | 74 ++++++++++++++++++++++++++++++++++++++++++++= ++++++-- > 2 files changed, 76 insertions(+), 2 deletions(-) >=20 > diff --git a/include/qemu/memfd.h b/include/qemu/memfd.h > index 8b1fe6a..950fb88 100644 > --- a/include/qemu/memfd.h > +++ b/include/qemu/memfd.h > @@ -17,4 +17,8 @@ > #define F_SEAL_WRITE 0x0008 /* prevent writes */ > #endif > =20 > +void *qemu_memfd_alloc(const char *name, size_t size, unsigned int sea= ls, > + int *fd); > +void qemu_memfd_free(void *ptr, size_t size, int fd); > + > #endif /* QEMU_MEMFD_H */ > diff --git a/util/memfd.c b/util/memfd.c > index a98d57e..8b2b785 100644 > --- a/util/memfd.c > +++ b/util/memfd.c > @@ -27,6 +27,14 @@ > =20 > #include "config-host.h" > =20 > +#include > +#include > + > +#include > +#include > +#include > +#include > + > #include "qemu/memfd.h" > =20 > #ifdef CONFIG_MEMFD > @@ -44,13 +52,75 @@ > #define MFD_ALLOW_SEALING 0x0002U > #endif > =20 > -static inline int memfd_create(const char *name, unsigned int flags) > +static int memfd_create(const char *name, unsigned int flags) > { > return syscall(__NR_memfd_create, name, flags); > } > #else /* !LINUX */ > -static inline int memfd_create(const char *name, unsigned int flags) > +static int memfd_create(const char *name, unsigned int flags) > { > return -1; > } > #endif > + > +void *qemu_memfd_alloc(const char *name, size_t size, unsigned int sea= ls, > + int *fd) > +{ > + void *ptr; > + int mfd; > + > + mfd =3D memfd_create(name, MFD_ALLOW_SEALING|MFD_CLOEXEC); Hmm. Does this interact correctly with the -mem-prealloc flag? > + if (mfd !=3D -1) { > + if (ftruncate(mfd, size) =3D=3D -1) { Any limitations on size? > + perror("ftruncate"); > + close(mfd); > + return NULL; > + } > + > + if (fcntl(mfd, F_ADD_SEALS, seals) =3D=3D -1) { > + perror("fcntl"); > + close(mfd); > + return NULL; > + } > + } else { > + const char *tmpdir =3D getenv("TMPDIR"); > + gchar *fname; > + > + tmpdir =3D tmpdir ? tmpdir : "/tmp"; > + > + fname =3D g_strdup_printf("%s/memfd-XXXXXX", tmpdir); This means there's now work to be done to set up selinux to allow QEMU creating memfd under /tmp. Maybe it's better to just fail gracefully for now. > + mfd =3D mkstemp(fname); > + unlink(fname); > + g_free(fname); > + > + if (mfd =3D=3D -1) { > + perror("mkstemp"); > + return NULL; > + } > + > + if (ftruncate(mfd, size) =3D=3D -1) { > + perror("ftruncate"); > + close(mfd); > + return NULL; > + } > + } > + > + ptr =3D mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, mfd, 0); Pls add space around | here and elsewhere. > + if (ptr =3D=3D MAP_FAILED) { > + perror("mmap"); > + close(mfd); > + return NULL; > + } > + > + *fd =3D mfd; > + return ptr; > +} > + > +void qemu_memfd_free(void *ptr, size_t size, int fd) > +{ > + if (ptr) { > + munmap(ptr, size); > + } > + > + close(fd); I notice you close fd unconditionally, but it's only returned on success above. So this will close an uninitialized one? > +} > --=20 > 2.4.3