[hwasan] Add test case for null pointer dereference (#122186)

This shows that HWASan will emit a memaccess intrinsic for null pointer
dereferences, with or without a fixed shadow.

This is a simplification of an internal bug report by dvyukov.

llvm/test/CodeGen/AArch64/hwasan-zero-ptr.ll

@@ -0,0 +1,65 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -filetype asm -o - %s | FileCheck %s
+
+; This shows that when dereferencing a null pointer, HWASan will call
+; __hwasan_check_x4294967071_19_fixed_0_short_v2
+; (N.B. 4294967071 == 2**32 - 239 + 14 == 2**32 - X0 + XZR
+;
+; The source was generated from llvm/test/Instrumentation/HWAddressSanitizer/zero-ptr.ll.
+
+; ModuleID = '<stdin>'
+source_filename = "<stdin>"
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64--linux-android10000"
+
+$hwasan.module_ctor = comdat any
+
+@__start_hwasan_globals = external hidden constant [0 x i8]
+@__stop_hwasan_globals = external hidden constant [0 x i8]
+@hwasan.note = private constant { i32, i32, i32, [8 x i8], i32, i32 } { i32 8, i32 8, i32 3, [8 x i8] c"LLVM\00\00\00\00", i32 trunc (i64 sub (i64 ptrtoint (ptr @__start_hwasan_globals to i64), i64 ptrtoint (ptr @hwasan.note to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @__stop_hwasan_globals to i64), i64 ptrtoint (ptr @hwasan.note to i64)) to i32) }, section ".note.hwasan.globals", comdat($hwasan.module_ctor), align 4
+
+; Function Attrs: sanitize_hwaddress
+define void @test_store_to_zeroptr() #0 {
+; CHECK-LABEL: test_store_to_zeroptr:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    str x30, [sp, #-16]! // 8-byte Folded Spill
+; CHECK-NEXT:    .cfi_def_cfa_offset 16
+; CHECK-NEXT:    .cfi_offset w30, -16
+; CHECK-NEXT:    bl __hwasan_check_x4294967071_19_fixed_0_short_v2
+; CHECK-NEXT:    mov x8, xzr
+; CHECK-NEXT:    mov w9, #42 // =0x2a
+; CHECK-NEXT:    str x9, [x8]
+; CHECK-NEXT:    ldr x30, [sp], #16 // 8-byte Folded Reload
+; CHECK-NEXT:    ret
+entry:
+  %.hwasan.shadow = call ptr asm "", "=r,0"(ptr null)
+  %b = inttoptr i64 0 to ptr
+  call void @llvm.hwasan.check.memaccess.shortgranules.fixedshadow(ptr %b, i32 19, i64 0)
+  store i64 42, ptr %b, align 8
+  ret void
+}
+
+; Function Attrs: nounwind
+declare void @llvm.hwasan.check.memaccess.shortgranules.fixedshadow(ptr, i32 immarg, i64 immarg) #1
+
+attributes #0 = { sanitize_hwaddress }
+attributes #1 = { nounwind }
+
+declare void @__hwasan_init()
+
+; Function Attrs: nounwind
+define internal void @hwasan.module_ctor() #1 comdat {
+; CHECK-LABEL: hwasan.module_ctor:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    str x30, [sp, #-16]! // 8-byte Folded Spill
+; CHECK-NEXT:    bl __hwasan_init
+; CHECK-NEXT:    ldr x30, [sp], #16 // 8-byte Folded Reload
+; CHECK-NEXT:    ret
+  call void @__hwasan_init()
+  ret void
+}
+
+!llvm.module.flags = !{!1}
+
+!0 = !{ptr @hwasan.note}
+!1 = !{i32 4, !"nosanitize_hwaddress", i32 1}

llvm/test/Instrumentation/HWAddressSanitizer/zero-ptr.ll

@@ -0,0 +1,35 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; RUN: opt < %s -passes=hwasan -S | FileCheck %s
+; RUN: opt < %s -passes=hwasan -hwasan-recover=0 -hwasan-mapping-offset=0 -S | FileCheck %s --check-prefixes=ABORT-ZERO-BASED-SHADOW
+
+; This shows that HWASan will emit a memaccess check when dereferencing a null
+; pointer.
+; The output is used as the source for llvm/test/CodeGen/AArch64/hwasan-zero-ptr.ll.
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64--linux-android10000"
+
+define void @test_store_to_zeroptr() sanitize_hwaddress {
+; CHECK-LABEL: define void @test_store_to_zeroptr
+; CHECK-SAME: () #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[DOTHWASAN_SHADOW:%.*]] = call ptr asm "", "=r,0"(ptr @__hwasan_shadow)
+; CHECK-NEXT:    [[B:%.*]] = inttoptr i64 0 to ptr
+; CHECK-NEXT:    call void @llvm.hwasan.check.memaccess.shortgranules(ptr [[DOTHWASAN_SHADOW]], ptr [[B]], i32 19)
+; CHECK-NEXT:    store i64 42, ptr [[B]], align 8
+; CHECK-NEXT:    ret void
+;
+; ABORT-ZERO-BASED-SHADOW-LABEL: define void @test_store_to_zeroptr
+; ABORT-ZERO-BASED-SHADOW-SAME: () #[[ATTR0:[0-9]+]] {
+; ABORT-ZERO-BASED-SHADOW-NEXT:  entry:
+; ABORT-ZERO-BASED-SHADOW-NEXT:    [[DOTHWASAN_SHADOW:%.*]] = call ptr asm "", "=r,0"(ptr null)
+; ABORT-ZERO-BASED-SHADOW-NEXT:    [[B:%.*]] = inttoptr i64 0 to ptr
+; ABORT-ZERO-BASED-SHADOW-NEXT:    call void @llvm.hwasan.check.memaccess.shortgranules.fixedshadow(ptr [[B]], i32 19, i64 0)
+; ABORT-ZERO-BASED-SHADOW-NEXT:    store i64 42, ptr [[B]], align 8
+; ABORT-ZERO-BASED-SHADOW-NEXT:    ret void
+;
+entry:
+  %b = inttoptr i64 0 to i64*
+  store i64 42, ptr %b
+  ret void
+}