0371dff995
When using the relative vtable ABI, if a vtable is not dso_local, it's given private linkage (if not COMDAT) or hidden visibility (if COMDAT) to make it dso_local (to place it in rodata instead of data.rel.ro), and an alias generated with the original linkage and visibility. This alias could later be removed from the symbol table, e.g. if using a version script, at which point we lose all symbol information about the vtable. Use internal linkage instead of private linkage to avoid this. While I'm here, clarify the comment about why COMDAT vtables can't use internal (or private) linkage, and associate it with the else block where hidden visibility is applied instead of internal linkage.
37 lines
2.0 KiB
C++
37 lines
2.0 KiB
C++
// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -o - -emit-llvm -fsanitize=hwaddress | FileCheck %s
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/// The usual vtable will have default visibility. In this case, the actual
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/// vtable is hidden and the alias is made public. With hwasan enabled, we want
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/// to ensure the local one self-referenced in the hidden vtable is not
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/// hwasan-instrumented.
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// CHECK-DAG: @_ZTV1A.local = internal unnamed_addr constant { [3 x i32] } { [3 x i32] [i32 0, i32 trunc (i64 sub (i64 ptrtoint (ptr @_ZTI1A.rtti_proxy to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [3 x i32] }, ptr @_ZTV1A.local, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @_ZN1A3fooEv to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [3 x i32] }, ptr @_ZTV1A.local, i32 0, i32 0, i32 2) to i64)) to i32)] }, no_sanitize_hwaddress, align 4
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// CHECK-DAG: @_ZTV1A = unnamed_addr alias { [3 x i32] }, ptr @_ZTV1A.local
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// CHECK-DAG: @_ZTI1A.rtti_proxy = linkonce_odr hidden unnamed_addr constant ptr @_ZTI1A, no_sanitize_hwaddress, comdat
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class A {
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public:
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virtual void foo();
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};
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void A::foo() {}
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void A_foo(A *a) {
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a->foo();
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}
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/// If the vtable happens to be hidden, then the alias is not needed. In this
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/// case, the original vtable struct itself should be unsanitized.
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// CHECK-DAG: @_ZTV1B = hidden unnamed_addr constant { [3 x i32] } { [3 x i32] [i32 0, i32 trunc (i64 sub (i64 ptrtoint (ptr @_ZTI1B.rtti_proxy to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [3 x i32] }, ptr @_ZTV1B, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @_ZN1B3fooEv to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [3 x i32] }, ptr @_ZTV1B, i32 0, i32 0, i32 2) to i64)) to i32)] }, no_sanitize_hwaddress, align 4
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// CHECK-DAG: @_ZTI1B.rtti_proxy = linkonce_odr hidden unnamed_addr constant ptr @_ZTI1B, no_sanitize_hwaddress, comdat
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class __attribute__((visibility("hidden"))) B {
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public:
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virtual void foo();
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};
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void B::foo() {}
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void B_foo(B *b) {
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b->foo();
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}
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