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/libc_errno.h"
20#include "src/__support/macros/sanitizer.h"
21
22namespace LIBC_NAMESPACE_DECL {
23
24LLVM_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

source code of libc/src/sys/socket/linux/recvfrom.cpp