On Thu, Aug 06, 2015 at 02:40:39PM +0200, marcandre.lur...@redhat.com wrote: > From: Marc-André Lureau <marcandre.lur...@redhat.com> > > Add qemu_memfd_alloc/free() helpers. > > The function helps to allocate and seal a memfd, and implements an > open/unlink/mmap fallback for system that do not support memfd. > > Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com> > --- > include/qemu/memfd.h | 4 +++ > util/memfd.c | 74 > ++++++++++++++++++++++++++++++++++++++++++++++++++-- > 2 files changed, 76 insertions(+), 2 deletions(-) > > 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 > > +void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals, > + 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 @@ > > #include "config-host.h" > > +#include <glib.h> > +#include <glib/gprintf.h> > + > +#include <stdio.h> > +#include <stdlib.h> > +#include <fcntl.h> > +#include <sys/mman.h> > + > #include "qemu/memfd.h" > > #ifdef CONFIG_MEMFD > @@ -44,13 +52,75 @@ > #define MFD_ALLOW_SEALING 0x0002U > #endif > > -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 seals, > + int *fd) > +{ > + void *ptr; > + int mfd; > + > + mfd = memfd_create(name, MFD_ALLOW_SEALING|MFD_CLOEXEC);
Hmm. Does this interact correctly with the -mem-prealloc flag? > + if (mfd != -1) { > + if (ftruncate(mfd, size) == -1) { Any limitations on size? > + perror("ftruncate"); > + close(mfd); > + return NULL; > + } > + > + if (fcntl(mfd, F_ADD_SEALS, seals) == -1) { > + perror("fcntl"); > + close(mfd); > + return NULL; > + } > + } else { > + const char *tmpdir = getenv("TMPDIR"); > + gchar *fname; > + > + tmpdir = tmpdir ? tmpdir : "/tmp"; > + > + fname = 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 = mkstemp(fname); > + unlink(fname); > + g_free(fname); > + > + if (mfd == -1) { > + perror("mkstemp"); > + return NULL; > + } > + > + if (ftruncate(mfd, size) == -1) { > + perror("ftruncate"); > + close(mfd); > + return NULL; > + } > + } > + > + ptr = mmap(0, size, PROT_READ|PROT_WRITE, MAP_SHARED, mfd, 0); Pls add space around | here and elsewhere. > + if (ptr == MAP_FAILED) { > + perror("mmap"); > + close(mfd); > + return NULL; > + } > + > + *fd = 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? > +} > -- > 2.4.3