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-rw-r--r--libc/sysdeps/linux/common/getentropy.c43
-rw-r--r--libc/sysdeps/linux/common/getrandom.c3
-rw-r--r--libc/sysdeps/linux/common/sys/random.h18
3 files changed, 61 insertions, 3 deletions
diff --git a/libc/sysdeps/linux/common/getentropy.c b/libc/sysdeps/linux/common/getentropy.c
new file mode 100644
index 000000000..971674c4f
--- /dev/null
+++ b/libc/sysdeps/linux/common/getentropy.c
@@ -0,0 +1,43 @@
+/*
+ * getentropy() by wrapping getrandom(), for µClibc-ng
+ *
+ * © 2025 mirabilos Ⓕ CC0 or MirBSD or GNU LGPLv2
+ *
+ * Note: may be a thread cancellation point, unlike the
+ * implementations in glibc and musl libc. Should this
+ * ever become a concern, it will need patching.
+ */
+
+#define _DEFAULT_SOURCE
+#include <errno.h>
+#include <unistd.h>
+#include <sys/random.h>
+
+int
+getentropy(void *__buf, size_t __len)
+{
+ ssize_t n;
+
+ if (__len > 256U) {
+ errno = EIO;
+ return (-1);
+ }
+
+ again:
+ if ((n = getrandom(__buf, __len, 0)) == -1)
+ switch (errno) {
+ case EAGAIN: /* should not happen but better safe than sorry */
+ case EINTR:
+ goto again;
+ default:
+ errno = EIO;
+ /* FALLTHROUGH */
+ case EFAULT:
+ case ENOSYS:
+ return (-1);
+ }
+ if ((size_t)n != __len)
+ /* also shouldn’t happen (safety net) */
+ goto again;
+ return (0);
+}
diff --git a/libc/sysdeps/linux/common/getrandom.c b/libc/sysdeps/linux/common/getrandom.c
index bb9841463..1db1663b9 100644
--- a/libc/sysdeps/linux/common/getrandom.c
+++ b/libc/sysdeps/linux/common/getrandom.c
@@ -8,6 +8,7 @@
#include <sys/syscall.h>
#include <sys/random.h>
+
#ifdef __NR_getrandom
-_syscall3(int, getrandom, void *, buf, size_t, buflen, unsigned int, flags)
+_syscall3(ssize_t, getrandom, void *, buf, size_t, buflen, unsigned int, flags)
#endif
diff --git a/libc/sysdeps/linux/common/sys/random.h b/libc/sysdeps/linux/common/sys/random.h
index 3d24e439b..c3d9cf575 100644
--- a/libc/sysdeps/linux/common/sys/random.h
+++ b/libc/sysdeps/linux/common/sys/random.h
@@ -4,11 +4,19 @@
#ifndef _SYS_RANDOM_H
#define _SYS_RANDOM_H 1
+
#include <features.h>
#include <stddef.h>
__BEGIN_DECLS
+#include <bits/types.h>
+
+#ifndef __ssize_t_defined
+typedef __ssize_t ssize_t;
+# define __ssize_t_defined
+#endif
+
#if defined __UCLIBC_LINUX_SPECIFIC__
# if 0 /*def __ASSUME_GETRANDOM_SYSCALL */
# include <linux/random.h>
@@ -26,9 +34,15 @@ __BEGIN_DECLS
# define GRND_RANDOM 0x0002
# define GRND_INSECURE 0x0004
# endif
-/* FIXME: aren't there a couple of __restrict and const missing ? */
-extern int getrandom(void *__buf, size_t count, unsigned int flags)
+extern ssize_t getrandom(void *__buf, size_t count, unsigned int flags)
__nonnull ((1)) __wur;
+
+/* OpenBSD-compatible access to random bytes.
+ May be a cancellation point here, unlike in glibc/musl. */
+# ifndef __getentropy_defined
+extern int getentropy(void *__buf, size_t __len) __nonnull ((1)) __wur;
+# define __getentropy_defined
+# endif
#endif
__END_DECLS