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/errno/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 20 namespace LIBC_NAMESPACE_DECL { 21 22 namespace { 23 24 bool 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 38 LLVM_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