[compiler-rt] [safestack] Enable for aarch64

[zatrazz]

Summary

This patch enables the safestack for aarch64. The frontend already have
it enabled on all supported architectures and no adjustment is required
in llvm.

The compiler-rt adjustments are basically add on the cmake configuration
to enable the tests and fix the pagesize debug check by getting its
value at runtime (since aarch64 has multiple pagesize depending of
kernel configuration).

All tests pass on aarch64-linux.

[zatrazz]

Ping.

[eugenis]

LGTM

[zatrazz]

I also pushed a patch (r255491) to disable the overflow.c check on AArch64 (the buildbot accuses an error which I can't currently reproduce in my environments).

cmake/config-ix.cmake

 set(ALL_DFSAN_SUPPORTED_ARCH ${X86_64} ${MIPS64} ${ARM64})
 set(ALL_LSAN_SUPPORTED_ARCH ${X86_64} ${MIPS64} ${ARM64})
 set(ALL_MSAN_SUPPORTED_ARCH ${X86_64} ${MIPS64} ${ARM64})
 set(ALL_PROFILE_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64} ${PPC64}
     ${MIPS32} ${MIPS64})
 set(ALL_TSAN_SUPPORTED_ARCH ${X86_64} ${MIPS64} ${ARM64})
 set(ALL_UBSAN_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64}
     ${MIPS32} ${MIPS64} ${PPC64})
-set(ALL_SAFESTACK_SUPPORTED_ARCH ${X86} ${X86_64})
+set(ALL_SAFESTACK_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM64})
 
 if(APPLE)
   include(CompilerRTDarwinUtils)
 
   # On Darwin if /usr/include doesn't exist, the user probably has Xcode but not
   # the command line tools. If this is the case, we need to find the OS X
   # sysroot to pass to clang.
   if(NOT EXISTS /usr/include)

lib/safestack/safestack.cc

 // during program execution.
 //
 //===----------------------------------------------------------------------===//
 
 #include <limits.h>
 #include <pthread.h>
 #include <stddef.h>
 #include <stdint.h>
+#include <unistd.h>
 #include <sys/resource.h>
 #include <sys/types.h>
 #include <sys/user.h>
 
 #include "interception/interception.h"
 #include "sanitizer_common/sanitizer_common.h"
 
 // TODO: The runtime library does not currently protect the safe stack beyond

 
 /// Minimum stack alignment for the unsafe stack.
 const unsigned kStackAlign = 16;
 
 /// Default size of the unsafe stack. This value is only used if the stack
 /// size rlimit is set to infinity.
 const unsigned kDefaultUnsafeStackSize = 0x2800000;
 
+/// Runtime page size obtained through sysconf
+static unsigned pageSize;
+
 // TODO: To make accessing the unsafe stack pointer faster, we plan to
 // eventually store it directly in the thread control block data structure on
 // platforms where this structure is pointed to by %fs or %gs. This is exactly
 // the same mechanism as currently being used by the traditional stack
 // protector pass to store the stack guard (see getStackCookieLocation()
 // function above). Doing so requires changing the tcbhead_t struct in glibc
 // on Linux and tcb struct in libc on FreeBSD.
 //
if (attr) {
     pthread_attr_init(&tmpattr);
     pthread_attr_getstacksize(&tmpattr, &size);
     pthread_attr_getguardsize(&tmpattr, &guard);
     pthread_attr_destroy(&tmpattr);
   }
 
   CHECK_NE(size, 0);
   CHECK_EQ((size & (kStackAlign - 1)), 0);
-  CHECK_EQ((guard & (PAGE_SIZE - 1)), 0);
+  CHECK_EQ((guard & (pageSize - 1)), 0);
 
   void *addr = unsafe_stack_alloc(size, guard);
   struct tinfo *tinfo =
       (struct tinfo *)(((char *)addr) + size - sizeof(struct tinfo));
   tinfo->start_routine = start_routine;
   tinfo->start_routine_arg = arg;
   tinfo->unsafe_stack_start = addr;
   tinfo->unsafe_stack_size = size;
void __safestack_init() {
   struct rlimit limit;
   if (getrlimit(RLIMIT_STACK, &limit) == 0 && limit.rlim_cur != RLIM_INFINITY)
     size = limit.rlim_cur;
 
   // Allocate unsafe stack for main thread
   void *addr = unsafe_stack_alloc(size, guard);
 
   unsafe_stack_setup(addr, size, guard);
+  pageSize = sysconf(_SC_PAGESIZE);
 
   // Initialize pthread interceptors for thread allocation
   INTERCEPT_FUNCTION(pthread_create);
 
   // Setup the cleanup handler
   pthread_key_create(&thread_cleanup_key, thread_cleanup_handler);
 }