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authorLennart Poettering <lennart@poettering.net>2014-10-29 17:06:32 +0100
committerLennart Poettering <lennart@poettering.net>2014-10-29 17:06:32 +0100
commit539618a0ddc2dc7f0fbe28de2ae0e07b34c81e60 (patch)
tree23a4a87b839413ee39636eb116b5316571c88878
parentd0159fdc7a1009027f019f763106aa13256cf030 (diff)
util: make use of the new getrandom() syscall if it is available when needing entropy
Doesn't require an fd, and could be a bit faster, so let's make use of it, if it is available.
-rw-r--r--configure.ac3
-rw-r--r--src/shared/missing.h15
-rw-r--r--src/shared/util.c25
3 files changed, 41 insertions, 2 deletions
diff --git a/configure.ac b/configure.ac
index f8a95cb9c8..82bc7a63ff 100644
--- a/configure.ac
+++ b/configure.ac
@@ -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,
diff --git a/src/shared/missing.h b/src/shared/missing.h
index bb4f8f23a8..5b87e23eec 100644
--- a/src/shared/missing.h
+++ b/src/shared/missing.h
@@ -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
diff --git a/src/shared/util.c b/src/shared/util.c
index 4143f6d643..ceafba86af 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -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)