tsan: Remove __pointer_chk_guard@GLIBC_PRIVATE requirement for AArch64

Current AArch64 {sig}{set,long}jmp interposing requires accessing glibc
private __pointer_chk_guard to get process xor mask to demangled the
internal {sig}jmp_buf function pointers.

It causes some packing issues, as described in gcc PR#71042 [1], and is
is not a godd practice to rely on a private glibc namespace (since ABI is
not meant to be stable).

This patch fixes it by changing how libtsan obtains the guarded pointer
value: at initialization a specific routine issues a setjmp call and
using the mangled function pointer and the original value derive the
random guarded pointer.

Checked on aarch64 39-bit VMA.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71042

llvm-svn: 278292

compiler-rt/lib/tsan/rtl/tsan_platform_linux.cc

@@ -38,6 +38,7 @@
 #include <sys/mman.h>
 #if SANITIZER_LINUX
 #include <sys/personality.h>
+#include <setjmp.h>
 #endif
 #include <sys/syscall.h>
 #include <sys/socket.h>
@@ -67,6 +68,10 @@ extern "C" void *__libc_stack_end;
 void *__libc_stack_end = 0;
 #endif
 
+#if SANITIZER_LINUX && defined(__aarch64__)
+void InitializeGuardPtr() __attribute__((visibility("hidden")));
+#endif
+
 namespace __tsan {
 
 #ifdef TSAN_RUNTIME_VMA
@@ -264,6 +269,8 @@ void InitializePlatform() {
       CHECK_NE(personality(old_personality | ADDR_NO_RANDOMIZE), -1);
       reexec = true;
     }
+    // Initialize the guard pointer used in {sig}{set,long}jump.
+    InitializeGuardPtr();
 #endif
     if (reexec)
       ReExec();

compiler-rt/lib/tsan/rtl/tsan_rtl_aarch64.S

@@ -1,6 +1,62 @@
 #include "sanitizer_common/sanitizer_asm.h"
+
+.section .bss
+.type	__tsan_pointer_chk_guard, %object
+.size	__tsan_pointer_chk_guard, 8
+__tsan_pointer_chk_guard:
+.zero	8
+
 .section .text
 
+// GLIBC mangles the function pointers in jmp_buf (used in {set,long}*jmp
+// functions) by XORing them with a random guard pointer.  For AArch64 it is a
+// global variable rather than a TCB one (as for x86_64/powerpc) and althought
+// its value is exported by the loader, it lies within a private GLIBC
+// namespace (meaning it should be only used by GLIBC itself and the ABI is
+// not stable). So InitializeGuardPtr obtains the pointer guard value by
+// issuing a setjmp and checking the resulting pointers values against the
+// original ones.
+.hidden _Z18InitializeGuardPtrv
+.global _Z18InitializeGuardPtrv
+.type _Z18InitializeGuardPtrv, @function
+_Z18InitializeGuardPtrv:
+  CFI_STARTPROC
+  // Allocates a jmp_buf for the setjmp call.
+  stp	x29, x30, [sp, -336]!
+  CFI_DEF_CFA_OFFSET (336)
+  CFI_OFFSET (29, -336)
+  CFI_OFFSET (30, -328)
+  add	x29, sp, 0
+  CFI_DEF_CFA_REGISTER (29)
+  add	x0, x29, 24
+
+  // Call libc setjmp that mangle the stack pointer value
+  adrp  x1, :got:_ZN14__interception12real__setjmpE
+  ldr   x1, [x1, #:got_lo12:_ZN14__interception12real__setjmpE]
+  ldr   x1, [x1]
+  blr   x1
+
+  // glibc setjmp mangles both the frame pointer (FP, pc+4 on blr) and the
+  // stack pointer (SP). FP will be placed on ((uintptr*)jmp_buf)[11] and
+  // SP at ((uintptr*)jmp_buf)[13].
+  // The mangle operation is just 'value' xor 'pointer guard value' and
+  // if we know the original value (SP) and the expected one, we can derive
+  // the guard pointer value.
+  mov	x0, sp
+
+  // Loads the mangled SP pointer.
+  ldr	x1, [x29, 128]
+  eor	x0, x0, x1
+  adrp	x2, __tsan_pointer_chk_guard
+  str	x0, [x2, #:lo12:__tsan_pointer_chk_guard]
+  ldp	x29, x30, [sp], 336
+  CFI_RESTORE (30)
+  CFI_RESTORE (19)
+  CFI_DEF_CFA (31, 0)
+  ret
+  CFI_ENDPROC
+.size _Z18InitializeGuardPtrv, .-_Z18InitializeGuardPtrv
+
 .hidden __tsan_setjmp
 .comm _ZN14__interception11real_setjmpE,8,8
 .type setjmp, @function
@@ -23,10 +79,9 @@ setjmp:
   mov     x19, x0
 
   // SP pointer mangling (see glibc setjmp)
-  adrp    x2, :got:__pointer_chk_guard
-  ldr     x2, [x2, #:got_lo12:__pointer_chk_guard]
+  adrp    x2, __tsan_pointer_chk_guard
+  ldr     x2, [x2, #:lo12:__tsan_pointer_chk_guard]
   add     x0, x29, 32
-  ldr     x2, [x2]
   eor     x1, x2, x0
 
   // call tsan interceptor
@@ -71,10 +126,9 @@ _setjmp:
   mov     x19, x0
 
   // SP pointer mangling (see glibc setjmp)
-  adrp    x2, :got:__pointer_chk_guard
-  ldr     x2, [x2, #:got_lo12:__pointer_chk_guard]
+  adrp    x2, __tsan_pointer_chk_guard
+  ldr     x2, [x2, #:lo12:__tsan_pointer_chk_guard]
   add     x0, x29, 32
-  ldr     x2, [x2]
   eor     x1, x2, x0
 
   // call tsan interceptor
@@ -121,10 +175,9 @@ sigsetjmp:
   mov     x19, x0
 
   // SP pointer mangling (see glibc setjmp)
-  adrp    x2, :got:__pointer_chk_guard
-  ldr     x2, [x2, #:got_lo12:__pointer_chk_guard]
+  adrp    x2, __tsan_pointer_chk_guard
+  ldr     x2, [x2, #:lo12:__tsan_pointer_chk_guard]
   add     x0, x29, 32
-  ldr     x2, [x2]
   eor     x1, x2, x0
 
   // call tsan interceptor
@@ -173,10 +226,9 @@ __sigsetjmp:
   mov     x19, x0
 
   // SP pointer mangling (see glibc setjmp)
-  adrp    x2, :got:__pointer_chk_guard
-  ldr     x2, [x2, #:got_lo12:__pointer_chk_guard]
+  adrp    x2, __tsan_pointer_chk_guard
+  ldr     x2, [x2, #:lo12:__tsan_pointer_chk_guard]
   add     x0, x29, 32
-  ldr     x2, [x2]
   eor     x1, x2, x0
 
   // call tsan interceptor