1 //===-- Linux implementation of pread -------------------------------------===// 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-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "src/unistd/pread.h" 10 11 #include "src/__support/OSUtil/syscall.h" // For internal syscall function. 12 #include "src/__support/common.h" 13 #include "src/__support/macros/sanitizer.h" // for MSAN_UNPOISON 14 #include "src/errno/libc_errno.h" 15 #include <stdint.h> // For uint64_t. 16 #include <sys/syscall.h> // For syscall numbers. 17 18 namespace LIBC_NAMESPACE { 19 20 LLVM_LIBC_FUNCTION(ssize_t, pread, 21 (int fd, void *buf, size_t count, off_t offset)) { 22 #ifdef LIBC_TARGET_ARCH_IS_RISCV32 23 static_assert(sizeof(off_t) == 8); 24 ssize_t ret = LIBC_NAMESPACE::syscall_impl<ssize_t>( 25 SYS_pread64, fd, buf, count, (long)offset, 26 (long)(((uint64_t)(offset)) >> 32)); 27 #else 28 ssize_t ret = LIBC_NAMESPACE::syscall_impl<ssize_t>(SYS_pread64, fd, buf, 29 count, offset); 30 #endif 31 // The cast is important since there is a check that dereferences the pointer 32 // which fails on void*. 33 MSAN_UNPOISON(reinterpret_cast<char *>(buf), count); 34 if (ret < 0) { 35 libc_errno = static_cast<int>(-ret); 36 return -1; 37 } 38 return ret; 39 } 40 41 } // namespace LIBC_NAMESPACE 42