sanitizer: Don't intercept ustat for Linux

[hjl.tools]

Summary

<sys/ustat.h> has been removed from glibc 2.28 by:

commit cf2478d53ad7071e84c724a986b56fe17f4f4ca7
Author: Adhemerval Zanella <[e-mail]>
Date: Sun Mar 18 11:28:59 2018 +0800

Deprecate ustat syscall interface

This patch removes its reference from libsanitizer for Linux to fix

https://bugs.llvm.org/show_bug.cgi?id=37418

[cryptoad]

Sorry I don't know enough about the ustat usages, resigning as a reviewer.

[kcc]

the ustat interceptor has been added in 2013, probably as part of the work on msan.

r190157 | eugenis | 2013-09-06 07:20:01 -0700 (Fri, 06 Sep 2013) | 2 lines
[sanitizer] A bunch of linux system call handlers.

I bet some code uses ustat and was causing msan false positives.
We don't seem to have tests for it, and such a test doesn't appear trivial for the LLVM test suite.

What will happen on pre 2.28 if we remove this interceptor?
Will msan get new false positives?

[hjl.tools]

I tested it on Fedora 28 which has glibc 2.27. There is no regression, probably because there is no test.
We can a definition of sizeof(struct ustat) to sanitizer_common/sanitizer_platform_limits_posix.cc, which
doesn't depend on <sys/ustat.h>.

[kcc]

Yes, I think a much safer fix would be to add

unsigned struct_ustat_sz = <SOMETHING>;  // glibc >= 2.28 doesn't have <sys/ustat.h> so we can't include it and use  sizeof(struct ustat);

[hjl.tools]

Replaced by

https://reviews.llvm.org/D47281

lib/sanitizer_common/sanitizer_common_syscalls.inc

 PRE_SYSCALL(newfstat)(long fd, void *statbuf) {}
 
 POST_SYSCALL(newfstat)(long res, long fd, void *statbuf) {
   if (res >= 0) {
     if (statbuf) POST_WRITE(statbuf, struct_kernel_stat_sz);
   }
 }
 
-#if !SANITIZER_ANDROID
+#if !SANITIZER_LINUX && !SANITIZER_ANDROID
 PRE_SYSCALL(ustat)(long dev, void *ubuf) {}
 
 POST_SYSCALL(ustat)(long res, long dev, void *ubuf) {
   if (res >= 0) {
     if (ubuf) POST_WRITE(ubuf, struct_ustat_sz);
   }
 }
 #endif  // !SANITIZER_ANDROID

lib/sanitizer_common/sanitizer_platform_limits_posix.cc

 #include <sys/kd.h>
 #include <sys/shm.h>
 #include <sys/statvfs.h>
 #include <sys/timex.h>
 #if defined(__mips64)
 # include <sys/procfs.h>
 #endif
 #include <sys/user.h>
-#include <sys/ustat.h>
 #include <linux/cyclades.h>
 #include <linux/if_eql.h>
 #include <linux/if_plip.h>
 #include <linux/lp.h>
 #include <linux/mroute.h>
 #include <linux/mroute6.h>
 #include <linux/scc.h>
 #include <linux/serial.h>

 #if SANITIZER_LINUX || SANITIZER_FREEBSD
   unsigned struct_rlimit_sz = sizeof(struct rlimit);
   unsigned struct_timespec_sz = sizeof(struct timespec);
   unsigned struct_utimbuf_sz = sizeof(struct utimbuf);
   unsigned struct_itimerspec_sz = sizeof(struct itimerspec);
 #endif // SANITIZER_LINUX || SANITIZER_FREEBSD
 
 #if SANITIZER_LINUX && !SANITIZER_ANDROID
-  unsigned struct_ustat_sz = sizeof(struct ustat);
   unsigned struct_rlimit64_sz = sizeof(struct rlimit64);
   unsigned struct_statvfs64_sz = sizeof(struct statvfs64);
 #endif // SANITIZER_LINUX && !SANITIZER_ANDROID
 
 #if (SANITIZER_LINUX || SANITIZER_FREEBSD) && !SANITIZER_ANDROID
   unsigned struct_timex_sz = sizeof(struct timex);
   unsigned struct_msqid_ds_sz = sizeof(struct msqid_ds);
   unsigned struct_mq_attr_sz = sizeof(struct mq_attr);