Message ID | 1443544494-28737-6-git-send-email-marcandre.lureau@redhat.com |
---|---|
State | New |
Headers | show |
On Tue, Sep 29, 2015 at 06:34:35PM +0200, marcandre.lureau@redhat.com wrote: > From: Marc-André Lureau <marcandre.lureau@redhat.com> > > Add qemu_memfd_alloc/free() helpers. > > The function helps to allocate and seal a memfd. > > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> > --- > include/qemu/memfd.h | 4 ++++ > util/memfd.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++-- > 2 files changed, 61 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..3168902 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 +52,60 @@ > #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; > + > + *fd = -1; > + mfd = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC); > + if (mfd != -1) { > + if (ftruncate(mfd, size) == -1) { > + perror("ftruncate"); > + close(mfd); > + return NULL; > + } > + > + if (fcntl(mfd, F_ADD_SEALS, seals) == -1) { > + perror("fcntl"); > + close(mfd); > + return NULL; > + } Why do it here? I note that you don't try to do this with the tmpfs fallback. > + } else { > + perror("memfd"); > + return NULL; > + } > + > + ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0); > + 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); > + } > + > + if (fd != -1) { > + close(fd); > + } > +} > -- > 2.4.3
----- Original Message ----- > On Tue, Sep 29, 2015 at 06:34:35PM +0200, marcandre.lureau@redhat.com wrote: > > From: Marc-André Lureau <marcandre.lureau@redhat.com> > > > > Add qemu_memfd_alloc/free() helpers. > > > > The function helps to allocate and seal a memfd. > > > > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> > > --- > > include/qemu/memfd.h | 4 ++++ > > util/memfd.c | 59 > > ++++++++++++++++++++++++++++++++++++++++++++++++++-- > > 2 files changed, 61 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..3168902 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 +52,60 @@ > > #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; > > + > > + *fd = -1; > > + mfd = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC); > > + if (mfd != -1) { > > + if (ftruncate(mfd, size) == -1) { > > + perror("ftruncate"); > > + close(mfd); > > + return NULL; > > + } > > + > > + if (fcntl(mfd, F_ADD_SEALS, seals) == -1) { > > + perror("fcntl"); > > + close(mfd); > > + return NULL; > > + } > > Why do it here? I note that you don't try to do this with the tmpfs > fallback. The idea of the helper is to use the best practices of using memfd: sealing, and provide graceful feedback if not available. Without sealing, there isn't much benefit over traditional open/mmap. If you want to use memfd differently, for ex to enforce sealing, then the helper isn't of much use. F_ADD_SEALS doesn't work on regular open/mmap shared memory, it was added with memfd afaik. Since some kernel support memfd without sealing, I'll add a fallback for that case. > > > + } else { > > + perror("memfd"); > > + return NULL; > > + } > > + > > + ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0); > > + 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); > > + } > > + > > + if (fd != -1) { > > + close(fd); > > + } > > +} > > -- > > 2.4.3 >
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..3168902 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 +52,60 @@ #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; + + *fd = -1; + mfd = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC); + if (mfd != -1) { + if (ftruncate(mfd, size) == -1) { + perror("ftruncate"); + close(mfd); + return NULL; + } + + if (fcntl(mfd, F_ADD_SEALS, seals) == -1) { + perror("fcntl"); + close(mfd); + return NULL; + } + } else { + perror("memfd"); + return NULL; + } + + ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0); + 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); + } + + if (fd != -1) { + close(fd); + } +}