[dfsan] Rename and fix an internal test issue for mmap+calloc

[stephan.yichao.zhao]

Summary

The linker suggests using -Wl,-z,notext.

Replaced assert by exit also fixed this.

After renaming, interceptor.c would be used to test interceptors in general by D101204.

[morehouse]

compiler-rt/test/dfsan/mmap_at_init.c

2

This test-only change is fine with me, but why do we need it in the first place? What relocation do we have marked read-only?

[stephan.yichao.zhao]

replaced assert by exit.

compiler-rt/test/dfsan/mmap_at_init.c

2

Not sure exactly which part causes the issue. It relates to assert: line 24 is assert.

ld.lld: error: can't create dynamic relocation R_X86_64_64 against local symbol in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
>>> defined in .../interceptors.c.tmp-calloc.o
>>> referenced by interceptors.c:24 (.../compiler-rt/test/dfsan/interceptors.c:24)
>>>               .../interceptors.c.tmp-calloc.o:(calloc)

Changed assert to an exit. Then it works.

[morehouse]

compiler-rt/test/dfsan/mmap_at_init.c

2

This is odd. @pcc, @eugenis: any idea why we get this linker error?

[stephan.yichao.zhao]

ping

[morehouse]

Change is fine with me, though I wish we understood why it's needed.

[stephan.yichao.zhao]

added comments

[stephan.yichao.zhao]

In D101649#2742217, @morehouse wrote:

Change is fine with me, though I wish we understood why it's needed.

still not sure why assert can cause link errors yet...
I added some comments in the test for reference.

compiler-rt/test/dfsan/mmap_at_init.c

 // RUN: %clang_dfsan -fno-sanitize=dataflow -DCALLOC -c %s -o %t-calloc.o
 // RUN: %clang_dfsan %s %t-calloc.o -o %t
 // RUN: %run %t
 //
 // REQUIRES: x86_64-target-arch
 //
 // Tests that calling mmap() during during dfsan initialization works.
 
-#include <assert.h>
 #include <sanitizer/dfsan_interface.h>
-#include <string.h>
 #include <sys/mman.h>
 #include <unistd.h>
 
 #ifdef CALLOC
 
 // dfsan_init() installs interceptors via dlysm(), which calls calloc().
 // Calling mmap() from here should work even if interceptors haven't been fully
 // set up yet.
 void *calloc(size_t Num, size_t Size) {
   size_t PageSize = getpagesize();
   Size = Size * Num;
   Size = (Size + PageSize - 1) & ~(PageSize - 1); // Round up to PageSize.
   void *Ret = mmap(NULL, Size, PROT_READ | PROT_WRITE,
                    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-  assert(Ret != MAP_FAILED);
+  // Use assert may cause link errors that require -Wl,-z,notext.
+  // Do not know the root cause yet.
+  if (Ret == MAP_FAILED) exit(-1);
   return Ret;
 }
 
 #else
 
 int main() { return 0; }
 
 #endif // CALLOC