llvm-svn: 176854

Summary:
The loader does not call mmap() through the PLT because it has to
bootstrap the process before libc is present.  Hooking dlopen() isn't
enough either because the loader runs module initializers before
returning, and they could run arbitrary msan instrumented code.

If msandr is present, then we can intercept the mmaps from dlopen at the
syscall layer and clear the shadow there.  If msandr is missing, we
clear the shadow after dlopen() and hope any initializers are trivial.

Reviewers: eugenis

CC: kcc, llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D509

llvm-svn: 176818

llvm-svn: 173910

llvm-svn: 173161

llvm-svn: 172069

llvm-svn: 172057

Check for conflicting memory mappings before attempting to map shadow.
Helps avoid segfault on Linux with disabled ASLR.

llvm-svn: 171100

Initial commit of the MemorySanitizer runtime library.

llvm-svn: 169858