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//===-- Linux implementation of getentropy --------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "src/unistd/getentropy.h"
#include "hdr/errno_macros.h"
#include "src/__support/OSUtil/syscall.h"
#include "src/__support/common.h"
#include "src/__support/libc_errno.h"
#include <sys/syscall.h> // For syscall numbers.
namespace LIBC_NAMESPACE_DECL {
LLVM_LIBC_FUNCTION(int, getentropy, (void *buffer, size_t length)) {
// check the length limit
if (length > 256) {
libc_errno = EIO;
return -1;
}
char *cursor = static_cast<char *>(buffer);
while (length != 0) {
// 0 flag means urandom and blocking, which meets the assumption of
// getentropy
auto ret = syscall_impl<long>(SYS_getrandom, cursor, length, 0);
// on success, advance the buffer pointer
if (ret >= 0) {
length -= static_cast<size_t>(ret);
cursor += ret;
continue;
}
auto error = -static_cast<int>(ret);
// on EINTR, try again
if (error == EINTR)
continue;
// on ENOSYS, forward errno and exit;
// otherwise, set EIO and exit
libc_errno = (error == ENOSYS) ? ENOSYS : EIO;
return -1;
}
return 0;
}
} // namespace LIBC_NAMESPACE_DECL
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