1 //===-- Linux implementation of recvfrom ----------------------------------===// 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/sys/socket/recvfrom.h" 10 11 #include <linux/net.h> // For SYS_SOCKET socketcall number. 12 #include <sys/syscall.h> // For syscall numbers. 13 14 #include "hdr/types/socklen_t.h" 15 #include "hdr/types/ssize_t.h" 16 #include "hdr/types/struct_sockaddr.h" 17 #include "src/__support/OSUtil/syscall.h" // For internal syscall function. 18 #include "src/__support/common.h" 19 #include "src/__support/macros/sanitizer.h" 20 #include "src/errno/libc_errno.h" 21 22 namespace LIBC_NAMESPACE_DECL { 23 24 LLVM_LIBC_FUNCTION(ssize_t, recvfrom, 25 (int sockfd, void *buf, size_t len, int flags, 26 sockaddr *__restrict src_addr, 27 socklen_t *__restrict addrlen)) { 28 // addrlen is a value-result argument. If it's not null, it passes the max 29 // size of the buffer src_addr to the syscall. After the syscall, it's updated 30 // to the actual size of the source address. This may be larger than the 31 // buffer, in which case the buffer contains a truncated result. 32 size_t srcaddr_sz; 33 if (src_addr) 34 srcaddr_sz = *addrlen; 35 (void)srcaddr_sz; // prevent "set but not used" warning 36 37 #ifdef SYS_recvfrom 38 ssize_t ret = LIBC_NAMESPACE::syscall_impl<ssize_t>( 39 SYS_recvfrom, sockfd, buf, len, flags, src_addr, addrlen); 40 #elif defined(SYS_socketcall) 41 unsigned long sockcall_args[6] = {static_cast<unsigned long>(sockfd), 42 reinterpret_cast<unsigned long>(buf), 43 static_cast<unsigned long>(len), 44 static_cast<unsigned long>(flags), 45 reinterpret_cast<unsigned long>(src_addr), 46 static_cast<unsigned long>(addrlen)}; 47 ssize_t ret = LIBC_NAMESPACE::syscall_impl<ssize_t>( 48 SYS_socketcall, SYS_RECVFROM, sockcall_args); 49 #else 50 #error "socket and socketcall syscalls unavailable for this platform." 51 #endif 52 if (ret < 0) { 53 libc_errno = static_cast<int>(-ret); 54 return -1; 55 } 56 57 MSAN_UNPOISON(buf, ret); 58 59 if (src_addr) { 60 size_t min_src_addr_size = (*addrlen < srcaddr_sz) ? *addrlen : srcaddr_sz; 61 (void)min_src_addr_size; // prevent "set but not used" warning 62 63 MSAN_UNPOISON(src_addr, min_src_addr_size); 64 } 65 return ret; 66 } 67 68 } // namespace LIBC_NAMESPACE_DECL 69