[PATCH] D30261: [Support] Provide linux/magic.h fallback for older kernels

[Michał Górny via Phabricator via llvm-commits]

mgorny created this revision.

The function for distinguishing local and remote files added in r295768
unconditionally uses linux/magic.h header to provide necessary
filesystem magic numbers. However, in kernel headers predating 2.6.18
the magic numbers are spread throughout multiple include files.
Furthermore, LLVM did not require kernel headers being installed so far.

To increase the portability across different versions of Linux kernel
and different Linux systems, add CMake header checks for linux/magic.h
and -- if it is missing -- the linux/nfs_fs.h and linux/smb.h headers
which contained the numbers previously.

Furthermore, since the numbers are static and the feature does not seem
critical enough to make LLVM require kernel headers at all, add fallback
constants for the case when none of the necessary headers is available.


Repository:
  rL LLVM

https://reviews.llvm.org/D30261

Files:
  cmake/config-ix.cmake
  lib/Support/Unix/Path.inc


Index: lib/Support/Unix/Path.inc
===================================================================
--- lib/Support/Unix/Path.inc
+++ lib/Support/Unix/Path.inc
@@ -76,7 +76,16 @@
 #include <sys/param.h>
 #include <sys/mount.h>
 #elif defined(__linux__)
+#if defined(HAVE_LINUX_MAGIC_H)
 #include <linux/magic.h>
+#else
+#if defined(HAVE_LINUX_NFS_FS_H)
+#include <linux/nfs_fs.h>
+#endif
+#if defined(HAVE_LINUX_SMB_H)
+#include <linux/smb.h>
+#endif
+#endif
 #include <sys/vfs.h>
 #else
 #include <sys/mount.h>
@@ -346,6 +355,12 @@
 
 static bool is_local_impl(struct STATVFS &Vfs) {
 #if defined(__linux__)
+#ifndef NFS_SUPER_MAGIC
+#define NFS_SUPER_MAGIC 0x6969
+#endif
+#ifndef SMB_SUPER_MAGIC
+#define SMB_SUPER_MAGIC 0x517B
+#endif
 #ifndef CIFS_MAGIC_NUMBER
 #define CIFS_MAGIC_NUMBER 0xFF534D42
 #endif
Index: cmake/config-ix.cmake
===================================================================
--- cmake/config-ix.cmake
+++ cmake/config-ix.cmake
@@ -88,6 +88,15 @@
     HAVE_CRASHREPORTER_INFO)
 endif()
 
+if(${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
+  check_include_file(linux/magic.h HAVE_LINUX_MAGIC_H)
+  if(NOT HAVE_LINUX_MAGIC_H)
+    # older kernels use split files
+    check_include_file(linux/nfs_fs.h HAVE_LINUX_NFS_FS_H)
+    check_include_file(linux/smb.h HAVE_LINUX_SMB_H)
+  endif()
+endif()
+
 # library checks
 if( NOT PURE_WINDOWS )
   check_library_exists(pthread pthread_create "" HAVE_LIBPTHREAD)


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