[libc-commits] [libc] [libc] Implement getentropy in sys/random (PR #226501)

[Pavel Labath via libc-commits]

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@@ -0,0 +1,49 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Linux implementation of the getentropy function.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/random/getentropy.h"
+
+#include "hdr/errno_macros.h"
+#include "hdr/types/size_t.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/getrandom.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, getentropy, (void *buffer, size_t length)) {
+  constexpr size_t MAX_BYTES = 256;
+  if (length > MAX_BYTES) {
+    libc_errno = EIO;
+    return -1;
+  }
+
+  auto *buf_ptr = reinterpret_cast<char *>(buffer);
+  size_t remaining = length;
+  while (remaining > 0) {
+    auto result = linux_syscalls::getrandom(buf_ptr, remaining, 0);
+    if (!result.has_value()) {
+      if (result.error() == EINTR)
+        continue;
+      libc_errno = static_cast<int>(result.error());
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labath wrote:

I believe this cast isn't needed.

https://github.com/llvm/llvm-project/pull/226501