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util: make use of the new getrandom() syscall if it is available when needing entropy

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Doesn't require an fd, and could be a bit faster, so let's make use of
it, if it is available.
This commit is contained in:
Lennart Poettering 2014-10-29 17:06:32 +01:00
parent d0159fdc7a
commit 539618a0dd
3 changed files with 41 additions and 2 deletions
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3
configure.ac
View File

@ -308,7 +308,7 @@ LIBS="$save_LIBS"
AC_CHECK_FUNCS([memfd_create])
AC_CHECK_FUNCS([__secure_getenv secure_getenv])
AC_CHECK_DECLS([gettid, pivot_root, name_to_handle_at, setns, LO_FLAGS_PARTSCAN],
AC_CHECK_DECLS([gettid, pivot_root, name_to_handle_at, setns, getrandom, LO_FLAGS_PARTSCAN],
[], [], [[
#include <sys/types.h>
#include <unistd.h>
@ -316,6 +316,7 @@ AC_CHECK_DECLS([gettid, pivot_root, name_to_handle_at, setns, LO_FLAGS_PARTSCAN]
#include <fcntl.h>
#include <sched.h>
#include <linux/loop.h>
#include <linux/random.h>
]])
AC_CHECK_DECLS([IFLA_MACVLAN_FLAGS,

15
src/shared/missing.h
View File

@ -140,6 +140,21 @@ static inline int memfd_create(const char *name, unsigned int flags) {
}
#endif
#ifndef __NR_getrandom
# if defined __x86_64__
# define __NR_getrandom 278
# else
# warning "__NR_getrandom unknown for your architecture"
# define __NR_getrandom 0xffffffff
# endif
#endif
#if !HAVE_DECL_GETRANDOM
static inline int getrandom(void *buffer, size_t count, unsigned flags) {
return syscall(__NR_getrandom, buffer, count, flags);
}
#endif
#ifndef BTRFS_IOCTL_MAGIC
#define BTRFS_IOCTL_MAGIC 0x94
#endif

25
src/shared/util.c
View File

@ -2466,14 +2466,37 @@ char* dirname_malloc(const char *path) {
}
int dev_urandom(void *p, size_t n) {
_cleanup_close_ int fd;
static int have_syscall = -1;
int r, fd;
ssize_t k;
/* Use the syscall unless we know we don't have it, or when
* the requested size is too large for it. */
if (have_syscall != 0 || (size_t) (int) n != n) {
r = getrandom(p, n, 0);
if (r == (int) n) {
have_syscall = true;
return 0;
}
if (r < 0) {
if (errno == ENOSYS)
/* we lack the syscall, continue with reading from /dev/urandom */
have_syscall = false;
else
return -errno;
} else
/* too short read? */
return -EIO;
}
fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (fd < 0)
return errno == ENOENT ? -ENOSYS : -errno;
k = loop_read(fd, p, n, true);
safe_close(fd);
if (k < 0)
return (int) k;
if ((size_t) k != n)