[PATCH 2/4] ASAN for MIPS: Correct struct_kernel_stat_sz for MIPS and don't use <sys/stat.h>.

[Hans-Peter Nilsson]

As mentioned in <http://gcc.gnu.org/ml/gcc/2018-03/msg00133.html>
the bogus adjustment to 160 from 144 (which is reverted here),
is a single-token commit in upstream r301307, an attempt to
correct a failed build due to an upstream change to compile the
runtime with D_FILE_OFFSET_BITS=64.  The correct fix is here:
just use the right include.  Yes, user-struct-stat64-as-stat is
actually 160 for MIPS o32 and I hear user-struct-stat is also
160 for n32.  There are additional fields appended for
user-struct-stat!  I guess for MIPS it's as bad as it gets for
mixing up kernel and user struct stat.  The context of the patch
doesn't show that in the #else there's the correct include, the
one for <asm/stat.h> to get the kernel-struct-stat.  If you
can't compile it, IMHO the kernel headers are just too old; 3.2
is fine for example.

This will be upstreamed, as soon as I find out the process.
It currently applies with some offsets to upstream, FWIW.

libsanitizer:
	* sanitizer_common/sanitizer_platform_limits_linux.cc: Do not
	take the shortcut to #include <sys/stat.h> for MIPS instead of
	the kernel <asm/stat.h>.  Explain why sys/stat.h is misleading
	or wrong to get the kernel struct stat.
	* sanitizer_common/sanitizer_platform_limits_posix.h [__mips__]:
	Correct the value for 32-bit non-android struct_kernel_stat_sz.

diff --git a/libsanitizer/sanitizer_common/sanitizer_platform_limits_linux.cc b/libsanitizer/sanitizer_common/sanitizer_platform_limits_linux.cc
index 23a0148..3a90653 100644
--- a/libsanitizer/sanitizer_common/sanitizer_platform_limits_linux.cc
+++ b/libsanitizer/sanitizer_common/sanitizer_platform_limits_linux.cc
@@ -25,9 +25,12 @@
 
 // With old kernels (and even new kernels on powerpc) asm/stat.h uses types that
 // are not defined anywhere in userspace headers. Fake them. This seems to work
-// fine with newer headers, too.
+// fine with newer headers, too.  Beware that with <sys/stat.h>, struct stat
+// takes the form of struct stat64 on 32-bit platforms if _FILE_OFFSET_BITS=64.
+// Also, for some platforms (e.g. mips) there are additional members in the
+// <sys/stat.h> struct stat:s.
 #include <linux/posix_types.h>
-#if defined(__x86_64__) ||  defined(__mips__)
+#if defined(__x86_64__)
 #include <sys/stat.h>
 #else
 #define ino_t __kernel_ino_t
diff --git a/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h b/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h
index 4d11d07..132e5e9 100644
--- a/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h
+++ b/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h
@@ -86,7 +86,7 @@ namespace __sanitizer {
 #elif defined(__mips__)
   const unsigned struct_kernel_stat_sz =
                  SANITIZER_ANDROID ? FIRST_32_SECOND_64(104, 128) :
-                                     FIRST_32_SECOND_64(160, 216);
+                                     FIRST_32_SECOND_64(144, 216);
   const unsigned struct_kernel_stat64_sz = 104;
 #elif defined(__s390__) && !defined(__s390x__)
   const unsigned struct_kernel_stat_sz = 64;
-- 
2.1.4

brgds, H-P