[Sanitizer][MIPS] internal_stat for mips64

[mohit.bhakkad]

Summary

For mips64, structure of the buffer after stat syscall is of kernel_stat, and we need to convert it to stat form.

[kcc]

interestingly, I don't see any uses of internal_lstat.
Does anyone know if we still need it?
Maybe we just delete it?

[samsonov]

We call internal_lstat() from internal symbolizer. I don't know if calling regular interceptor would work there (adding Dmitry).

[samsonov]

lib/sanitizer_common/sanitizer_linux.cc

192

Use

#if defined(__mips64)

219

Nest compiler directives like this:

#if FOO
# if BAR
   // code
 # endif
#endif

lib/sanitizer_common/sanitizer_platform.h

121 ↗

(On Diff #16600)

Is there no header you can #include in sanitizer_linux.cc on MIPS to get the definition of this structure?

In any case, this is the wrong place for the declaration. If you absolutely must provide the declaration, move it to sanitizer_platform_limits_posix.h

[mohit.bhakkad]

Changes in this revision:

• Including asm/stat.h to get definition of kernel_stat

[samsonov]

lib/sanitizer_common/sanitizer_linux.cc

51

Please turn this comment into a few regular english sentences with proper punctuation. It's hard to understand it otherwise.

[mohit.bhakkad]

lib/sanitizer_common/sanitizer_linux.cc

51

Hi @samsonov, is it OK to write it like:

/* For mips64, syscall(__NR_stat) fills the buffer in the 'struct kernel_stat' format. 
   Struct kernel_stat is defined as 'struct stat' in asm/stat.h. To access stat from 
   asm/stat.h, without conflicting with definition in sys/stat.h, we use this trick. */

[samsonov]

LGTM

lib/sanitizer_common/sanitizer_linux.cc

51

Alright, I see what you mean now :) (but use //-style comments)

[mohit.bhakkad]

Changes in this revision:

• Updated the comment/explanation as suggested

[samsonov]

LGTM

[mohit.bhakkad]

In D6385#23, @samsonov wrote:

LGTM

Thanks @samsonov
I don't have commit access, can you please commit it for me?

[dsanders]

I haven't been following the sanitizer reviews particularly closely but from what I've seen yourself and Kumar have been cooperating with the review process properly. If the others agree, perhaps it's time to request commit access.

[kcc]

If the others agree, perhaps it's time to request commit access.

Yes, I'd support granting post-review commit rights to Mohit.

[mohit.bhakkad]

Committed in rL224326

lib/sanitizer_common/sanitizer_linux.cc

 #include "sanitizer_procmaps.h"
 #include "sanitizer_stacktrace.h"
 #include "sanitizer_symbolizer.h"
 
 #if !SANITIZER_FREEBSD
 #include <asm/param.h>
 #endif
 
+// For mips64, syscall(__NR_stat) fills the buffer in the 'struct kernel_stat'
+// format. Struct kernel_stat is defined as 'struct stat' in asm/stat.h. To
+// access stat from asm/stat.h, without conflicting with definition in
+// sys/stat.h, we use this trick.
+#if defined(__mips64)
+#include <sys/types.h>
+#define stat kernel_stat
+#include <asm/stat.h>
+#undef stat
+#endif
+
 #include <dlfcn.h>
 #include <errno.h>
 #include <fcntl.h>
 #if !SANITIZER_ANDROID
 #include <link.h>
 #endif
 #include <pthread.h>
 #include <sched.h>
 #include <sys/mman.h>
 #include <sys/ptrace.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <unistd.h>
static void stat64_to_stat(struct stat64 *in, struct stat *out) {
   out->st_blocks = in->st_blocks;
   out->st_atime = in->st_atime;
   out->st_mtime = in->st_mtime;
   out->st_ctime = in->st_ctime;
   out->st_ino = in->st_ino;
 }
 #endif
 
+#if defined(__mips64)
+static void kernel_stat_to_stat(struct kernel_stat *in, struct stat *out) {
+  internal_memset(out, 0, sizeof(*out));
+  out->st_dev = in->st_dev;
+  out->st_ino = in->st_ino;
+  out->st_mode = in->st_mode;
+  out->st_nlink = in->st_nlink;
+  out->st_uid = in->st_uid;
+  out->st_gid = in->st_gid;
+  out->st_rdev = in->st_rdev;
+  out->st_size = in->st_size;
+  out->st_blksize = in->st_blksize;
+  out->st_blocks = in->st_blocks;
+  out->st_atime = in->st_atime_nsec;
+  out->st_mtime = in->st_mtime_nsec;
+  out->st_ctime = in->st_ctime_nsec;
+  out->st_ino = in->st_ino;
+}
+#endif
+
 uptr internal_stat(const char *path, void *buf) {
 #if SANITIZER_FREEBSD
   return internal_syscall(SYSCALL(stat), path, buf);
 #elif SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
   return internal_syscall(SYSCALL(newfstatat), AT_FDCWD, (uptr)path,
                           (uptr)buf, 0);
 #elif SANITIZER_LINUX_USES_64BIT_SYSCALLS
+# if defined(__mips64)
+  // For mips64, stat syscall fills buffer in the format of kernel_stat
+  struct kernel_stat kbuf;
+  int res = internal_syscall(SYSCALL(stat), path, &kbuf);
+  kernel_stat_to_stat(&kbuf, (struct stat *)buf);
+  return res;
+# else
   return internal_syscall(SYSCALL(stat), (uptr)path, (uptr)buf);
+# endif
 #else
   struct stat64 buf64;
   int res = internal_syscall(SYSCALL(stat64), path, &buf64);
   stat64_to_stat(&buf64, (struct stat *)buf);
   return res;
 #endif
 }