52 lines · cpp
1//===-- Linux implementation of getentropy --------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#include "src/unistd/getentropy.h"10#include "hdr/errno_macros.h"11#include "src/__support/OSUtil/syscall.h"12#include "src/__support/common.h"13#include "src/__support/libc_errno.h"14 15#include <sys/syscall.h> // For syscall numbers.16 17namespace LIBC_NAMESPACE_DECL {18LLVM_LIBC_FUNCTION(int, getentropy, (void *buffer, size_t length)) {19 // check the length limit20 if (length > 256) {21 libc_errno = EIO;22 return -1;23 }24 25 char *cursor = static_cast<char *>(buffer);26 while (length != 0) {27 // 0 flag means urandom and blocking, which meets the assumption of28 // getentropy29 auto ret = syscall_impl<long>(SYS_getrandom, cursor, length, 0);30 31 // on success, advance the buffer pointer32 if (ret >= 0) {33 length -= static_cast<size_t>(ret);34 cursor += ret;35 continue;36 }37 38 auto error = -static_cast<int>(ret);39 40 // on EINTR, try again41 if (error == EINTR)42 continue;43 44 // on ENOSYS, forward errno and exit;45 // otherwise, set EIO and exit46 libc_errno = (error == ENOSYS) ? ENOSYS : EIO;47 return -1;48 }49 return 0;50}51} // namespace LIBC_NAMESPACE_DECL52