[compiler-rt][aarch64] Add PAC-RET/BTI support to HWASAN.

[danielkiss]

Summary

Support for -mbranch-protection.

[eugenis]

LGTM

compiler-rt/lib/builtins/assembly.h

#define GNU_PROPERTY(type, value)                                              \
   .asciz "GNU" SEPARATOR                                                       \
   .word type SEPARATOR                                                         \
   .word 4 SEPARATOR                                                            \
   .word value SEPARATOR                                                        \
   .word 0 SEPARATOR                                                            \
   .popsection
 
 #if BTI_FLAG != 0
-#define BTI_C bti c
+#define BTI_C hint #34
+#define BTI_J hint #36
 #else
 #define BTI_C
+#define BTI_J
 #endif
 
 #if (BTI_FLAG | PAC_FLAG) != 0
 #define GNU_PROPERTY_BTI_PAC                                                   \
   GNU_PROPERTY(GNU_PROPERTY_AARCH64_FEATURE_1_AND, BTI_FLAG | PAC_FLAG)
 #else
 #define GNU_PROPERTY_BTI_PAC
 #endif

compiler-rt/lib/hwasan/hwasan_setjmp.S

 //===-- hwasan_setjmp.S --------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file is a part of HWAddressSanitizer.
 //
 // HWAddressSanitizer runtime.
 //===----------------------------------------------------------------------===//
 
 #include "sanitizer_common/sanitizer_asm.h"
+#include "builtins/assembly.h"
 
 #if HWASAN_WITH_INTERCEPTORS && defined(__aarch64__)
 #include "sanitizer_common/sanitizer_platform.h"
 
 // We want to save the context of the calling function.
 // That requires
 // 1) No modification of the link register by this function.
 // 2) No modification of the stack pointer by this function.
 // 3) (no modification of any other saved register, but that's not really going
 // to occur, and hence isn't as much of a worry).
 //
 // There's essentially no way to ensure that the compiler will not modify the
 // stack pointer when compiling a C function.
 // Hence we have to write this function in assembly.
 
 .section .text
 .file "hwasan_setjmp.S"
 
 .global __interceptor_setjmp
 ASM_TYPE_FUNCTION(__interceptor_setjmp)
 __interceptor_setjmp:
   CFI_STARTPROC
+  BTI_C
   mov x1, #0
   b __interceptor_sigsetjmp
   CFI_ENDPROC
 ASM_SIZE(__interceptor_setjmp)
 
 #if SANITIZER_ANDROID
 // Bionic also defines a function `setjmp` that calls `sigsetjmp` saving the
 // current signal.
 .global __interceptor_setjmp_bionic
 ASM_TYPE_FUNCTION(__interceptor_setjmp_bionic)
 __interceptor_setjmp_bionic:
   CFI_STARTPROC
+  BTI_C
   mov x1, #1
   b __interceptor_sigsetjmp
   CFI_ENDPROC
 ASM_SIZE(__interceptor_setjmp_bionic)
 #endif
 
 .global __interceptor_sigsetjmp
 ASM_TYPE_FUNCTION(__interceptor_sigsetjmp)
 __interceptor_sigsetjmp:
   CFI_STARTPROC
+  BTI_C
   stp x19, x20, [x0, #0<<3]
   stp x21, x22, [x0, #2<<3]
   stp x23, x24, [x0, #4<<3]
   stp x25, x26, [x0, #6<<3]
   stp x27, x28, [x0, #8<<3]
   stp x29, x30, [x0, #10<<3]
   stp  d8,  d9, [x0, #14<<3]
   stp d10, d11, [x0, #16<<3]

 #endif
 
 ALIAS __interceptor_setjmp, _setjmp
 .weak _setjmp
 #endif
 
 // We do not need executable stack.
 NO_EXEC_STACK_DIRECTIVE
+
+GNU_PROPERTY_BTI_PAC

compiler-rt/lib/hwasan/hwasan_tag_mismatch_aarch64.S

 #include "sanitizer_common/sanitizer_asm.h"
+#include "builtins/assembly.h"
 
 // The content of this file is AArch64-only:
 #if defined(__aarch64__)
 
 // The responsibility of the HWASan entry point in compiler-rt is to primarily
 // readjust the stack from the callee and save the current register values to
 // the stack.
 // This entry point function should be called from a __hwasan_check_* symbol.

 // clobbering the x17 register in error reports, and that the program will have
 // a runtime dependency on the __hwasan_tag_mismatch_v2 symbol therefore it will
 // fail to start up given an older (i.e. incompatible) runtime.
 .section .text
 .file "hwasan_tag_mismatch_aarch64.S"
 .global __hwasan_tag_mismatch
 .type __hwasan_tag_mismatch, %function
 __hwasan_tag_mismatch:
+  BTI_J
+
   // Compute the granule position one past the end of the access.
   mov x16, #1
   and x17, x1, #0xf
   lsl x16, x16, x17
   and x17, x0, #0xf
   add x17, x16, x17
 
   // Load the shadow byte again and check whether it is a short tag within the
__hwasan_tag_mismatch:
   // call and resume execution.
   ldp x0, x1, [sp], #256
   ret
 
 .global __hwasan_tag_mismatch_v2
 .type __hwasan_tag_mismatch_v2, %function
 __hwasan_tag_mismatch_v2:
   CFI_STARTPROC
+  BTI_J
 
   // Set the CFA to be the return address for caller of __hwasan_check_*. Note
   // that we do not emit CFI predicates to describe the contents of this stack
   // frame, as this proxy entry point should never be debugged. The contents
   // are static and are handled by the unwinder after calling
   // __hwasan_tag_mismatch. The frame pointer is already correctly setup
   // by __hwasan_check_*.
   add x29, sp, #232

 
 .Lfunc_end0:
   .size __hwasan_tag_mismatch, .Lfunc_end0-__hwasan_tag_mismatch
 
 #endif  // defined(__aarch64__)
 
 // We do not need executable stack.
 NO_EXEC_STACK_DIRECTIVE
+
+GNU_PROPERTY_BTI_PAC