[Arm][libsanitizer] Fix arm libsanitizer failure with bleeding edge glibc

[tnfchris]

Summary

Glibc has recently introduced changed to the mode field in ipc_perm in commit 2f959dfe849e0646e27403f2e4091536496ac0f0. For Arm this means that the mode field no longer has the same size.

This causes an assert failure against libsanitizer's internal copy of ipc_perm. Since this change can't be easily detected I am adding arm to the list of targets that are excluded from this check.

[tellenbach]

Please update the patch with more context, i.e., run git diff -U99999 or something similar. See https://llvm.org/docs/Phabricator.html#requesting-a-review-via-the-web-interface

[tnfchris]

Add more context, to diff.

[eugenis]

LGTM
We only really care about the size of struct shmid_ds AFAIK, not any of its fields individually.

[jakubjelinek]

The change looks wrong, the upcoming glibc 2.31 changes aren't just about ARM, but actually most of the architectures, so adding a special case just for ARM is just weird.
Either we should change the structures to match what glibc 2.31 will have and disable this ipc_perm mode checking if not __GLIBC_PREREQ (2, 31) on SANITIZER_LINUX,
or the check needs to be disabled on most Linux architectures.
Affected are e.g. x86_64, i?86, riscv*, sparc 32-bit, s390 31-bit, arm. And, on arm big endian and s390 31-bit there is even an important ABI change, so shmctl interception
won't be able to use dlsym but will need to use dlvsym.
Completely untested patch would be something like:

• sanitizer_common/sanitizer_platform_limits_posix.h 2019-11-07 17:56:23.530835549 +0100

+++ sanitizer_common/sanitizer_platform_limits_posix.h 2019-11-12 12:22:26.314511706 +0100
@@ -207,26 +207,13 @@ struct __sanitizer_ipc_perm {

u64 __unused1;                                                                                                                                  
u64 __unused2;

#elif defined(sparc)
-#if defined(arch64)

unsigned mode;

• unsigned short __pad1;

-#else

• unsigned short __pad1;
• unsigned short mode; unsigned short __pad2;

-#endif

unsigned short __seq;                                                                                                                           
unsigned long long __unused1;                                                                                                                   
unsigned long long __unused2;

-#elif defined(mips) || defined(aarch64) || defined(s390x)

• unsigned int mode;
• unsigned short __seq;
• unsigned short __pad1;
• unsigned long __unused1;
• unsigned long __unused2; #else
• unsigned short mode;
• unsigned short __pad1;

+ unsigned int mode;

unsigned short __seq;                                                                                                                           
unsigned short __pad2;

#if defined(x86_64) && !defined(_LP64)
---sanitizer_common/sanitizer_platform_limits_posix.cpp 2019-11-07 17:56:23.551835239 +0100
+++ sanitizer_common/sanitizer_platform_limits_posix.cpp 2019-11-12 12:23:42.959358844 +0100
@@ -1128,11 +1128,9 @@ CHECK_SIZE_AND_OFFSET(ipc_perm, uid);
CHECK_SIZE_AND_OFFSET(ipc_perm, gid);
CHECK_SIZE_AND_OFFSET(ipc_perm, cuid);
CHECK_SIZE_AND_OFFSET(ipc_perm, cgid);
-#if (!defined(aarch64) || !SANITIZER_LINUX || __GLIBC_PREREQ (2, 21)) && \

• !defined(arm)

-/* On aarch64 glibc 2.20 and earlier provided incorrect mode field. */
-/* On Arm newer glibc provide a different mode field, it's hard to detect

• so just disable the check. */

+#if !SANITIZER_LINUX || __GLIBC_PREREQ (2, 31)
+/* glibc 2.30 and earlier provided 16-bit mode field instead of 32-bit
+ on most architectures. */
CHECK_SIZE_AND_OFFSET(ipc_perm, mode);
#endif

compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.cpp

 # else
 CHECK_SIZE_AND_OFFSET(ipc_perm, __key);
 CHECK_SIZE_AND_OFFSET(ipc_perm, __seq);
 # endif
 CHECK_SIZE_AND_OFFSET(ipc_perm, uid);
 CHECK_SIZE_AND_OFFSET(ipc_perm, gid);
 CHECK_SIZE_AND_OFFSET(ipc_perm, cuid);
 CHECK_SIZE_AND_OFFSET(ipc_perm, cgid);
-#if !defined(__aarch64__) || !SANITIZER_LINUX || __GLIBC_PREREQ (2, 21)
+#if (!defined(__aarch64__) || !SANITIZER_LINUX || __GLIBC_PREREQ (2, 21)) && \
+    !defined(__arm__)
 /* On aarch64 glibc 2.20 and earlier provided incorrect mode field.  */
+/* On Arm newer glibc provide a different mode field, it's hard to detect
+   so just disable the check.  */
 CHECK_SIZE_AND_OFFSET(ipc_perm, mode);
 #endif
 
 CHECK_TYPE_SIZE(shmid_ds);
 CHECK_SIZE_AND_OFFSET(shmid_ds, shm_perm);
 CHECK_SIZE_AND_OFFSET(shmid_ds, shm_segsz);
 CHECK_SIZE_AND_OFFSET(shmid_ds, shm_atime);
 CHECK_SIZE_AND_OFFSET(shmid_ds, shm_dtime);