[lsan][test] Obtaining page size using sysconf(_SC_PAGESIZE)

[Ami-zhang]

Summary

The effectiveness of the mprotect function depends on whether
the first argument is aligned to a page boundary. If mprotect
doesn't work, the kernel will not generate a SIGSEGV signal for
the process when the calling process tries to access memory in
a manner that violates the protection. If so, this test fails.

The problem for this test is that it uses a fixed 4 kB page size
and is aligned. This fails when the page size is not 4 kB. For
example, this fails on LoongArch which uses a 16 kB pagesize.

[SixWeining]

LGTM and wait for others.

[xen0n]

Although I'd name the variable pagesize_mask if doing this myself, I'm not particularly picky about this. Apparently we can expect people to understand that a power-of-2 minus one automatically becomes a mask...

[MaskRay]

compiler-rt/test/lsan/TestCases/Linux/leak_check_segv.cpp

2

We don't use clang-format markers in tests. And we don't clang-format tests.

[Ami-zhang]

In D148407#4281082, @xen0n wrote:

Although I'd name the variable pagesize_mask if doing this myself, I'm not particularly picky about this. Apparently we can expect people to understand that a power-of-2 minus one automatically becomes a mask...

Okay, thanks for your suggestion. I have modified it.

compiler-rt/test/lsan/TestCases/Linux/leak_check_segv.cpp

2

Ok.

[Ami-zhang]

Addressed @xen0n's and @MaskRay's comments.

[Ami-zhang]

Clang-format this file.

compiler-rt/test/lsan/TestCases/Linux/leak_check_segv.cpp

 // Test that SIGSEGV during leak checking does not crash the process.
 // RUN: %clangxx_lsan -O1 %s -o %t && not %run %t 2>&1 | FileCheck %s
 // UNSUPPORTED: ppc
-#include <stdlib.h>
+#include <sanitizer/lsan_interface.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <sys/mman.h>
-#include <sanitizer/lsan_interface.h>
+#include <unistd.h>
 
 char data[10 * 1024 * 1024];
 
 int main() {
+  long pagesize_mask = sysconf(_SC_PAGESIZE) - 1;
   void *p = malloc(10 * 1024 * 1024);
   // surprise-surprise!
-  mprotect((void*)(((unsigned long)p + 4095) & ~4095), 16 * 1024, PROT_NONE);
-  mprotect((void*)(((unsigned long)data + 4095) & ~4095), 16 * 1024, PROT_NONE);
+  mprotect((void *)(((unsigned long)p + pagesize_mask) & ~pagesize_mask),
+           16 * 1024, PROT_NONE);
+  mprotect((void *)(((unsigned long)data + pagesize_mask) & ~pagesize_mask),
+           16 * 1024, PROT_NONE);
   __lsan_do_leak_check();
   fprintf(stderr, "DONE\n");
 }
 
 // CHECK: Tracer caught signal 11
 // CHECK: LeakSanitizer has encountered a fatal error
 // CHECK: HINT: For debugging, try setting {{.*}} LSAN_OPTIONS
 // CHECK-NOT: DONE