libc/src/sys/mman/linux/shm_common.h

   1 //===---------- Shared implementations for shm_open/shm_unlink ------------===//
   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/__support/CPP/array.h"
  10 #include "src/__support/CPP/optional.h"
  11 #include "src/__support/CPP/string_view.h"
  12 #include "src/__support/macros/config.h"
  13 #include "src/errno/libc_errno.h"
  14 #include "src/string/memory_utils/inline_memcpy.h"
  15
  16 // TODO: Get PATH_MAX via https://github.com/llvm/llvm-project/issues/85121
  17 #include <linux/limits.h>
  18
  19 namespace LIBC_NAMESPACE_DECL {
  20
  21 namespace shm_common {
  22
  23 LIBC_INLINE_VAR constexpr cpp::string_view SHM_PREFIX = "/dev/shm/";
  24 using SHMPath = cpp::array<char, NAME_MAX + SHM_PREFIX.size() + 1>;
  25
  26 LIBC_INLINE cpp::optional<SHMPath> translate_name(cpp::string_view name) {
  27   // trim leading slashes
  28   size_t offset = name.find_first_not_of('/');
  29   if (offset == cpp::string_view::npos) {
  30     libc_errno = EINVAL;
  31     return cpp::nullopt;
  32   }
  33   name = name.substr(offset);
  34
  35   // check the name
  36   if (name.size() > NAME_MAX) {
  37     libc_errno = ENAMETOOLONG;
  38     return cpp::nullopt;
  39   }
  40   if (name == "." || name == ".." || name.contains('/')) {
  41     libc_errno = EINVAL;
  42     return cpp::nullopt;
  43   }
  44
  45   // prepend the prefix
  46   SHMPath buffer;
  47   inline_memcpy(buffer.data(), SHM_PREFIX.data(), SHM_PREFIX.size());
  48   inline_memcpy(buffer.data() + SHM_PREFIX.size(), name.data(), name.size());
  49   buffer[SHM_PREFIX.size() + name.size()] = '\0';
  50   return buffer;
  51 }
  52 } // namespace shm_common
  53
  54 } // namespace LIBC_NAMESPACE_DECL