1//===-- Linux implementation of getcwd ------------------------------------===//
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/getcwd.h"
10
11#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
12#include "src/__support/common.h"
13#include "src/__support/macros/config.h"
14#include "src/string/allocating_string_utils.h" // For strdup.
15
16#include "src/__support/libc_errno.h"
17#include <linux/limits.h> // This is safe to include without any name pollution.
18#include <sys/syscall.h> // For syscall numbers.
19
20namespace LIBC_NAMESPACE_DECL {
21
22namespace {
23
24bool getcwd_syscall(char *buf, size_t size) {
25 int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_getcwd, buf, size);
26 if (ret < 0) {
27 libc_errno = -ret;
28 return false;
29 } else if (ret == 0 || buf[0] != '/') {
30 libc_errno = ENOENT;
31 return false;
32 }
33 return true;
34}
35
36} // anonymous namespace
37
38LLVM_LIBC_FUNCTION(char *, getcwd, (char *buf, size_t size)) {
39 if (buf == nullptr) {
40 // We match glibc's behavior here and return the cwd in a malloc-ed buffer.
41 // We will allocate a static buffer of size PATH_MAX first and fetch the cwd
42 // into it. This way, if the syscall fails, we avoid unnecessary malloc
43 // and free.
44 char pathbuf[PATH_MAX];
45 if (!getcwd_syscall(pathbuf, PATH_MAX))
46 return nullptr;
47 auto cwd = internal::strdup(pathbuf);
48 if (!cwd) {
49 libc_errno = ENOMEM;
50 return nullptr;
51 }
52 return *cwd;
53 } else if (size == 0) {
54 libc_errno = EINVAL;
55 return nullptr;
56 }
57
58 // TODO: When buf is not sufficient, evaluate the full cwd path using
59 // alternate approaches.
60
61 if (!getcwd_syscall(buf, size))
62 return nullptr;
63 return buf;
64}
65
66} // namespace LIBC_NAMESPACE_DECL
67

source code of libc/src/unistd/linux/getcwd.cpp