[PAC] `arm64e` platform does not set ptrauth attributes properly

[asl]

Consider the following code:

int f() {
  thread_local int j = 0;
  j++;
  return j;
}

Running clang++ tls.cpp -S -O1 -target arm64e-apple-darwin yields:

Lloh0:
        adrp    x0, __ZZ1fvE1j@TLVPPAGE
Lloh1:
        ldr     x0, [x0, __ZZ1fvE1j@TLVPPAGEOFF]
        ldr     x8, [x0]
        blr     x8
        ldr     w8, [x0]
        add     w8, w8, #1
        str     w8, [x0]
        mov     x0, x8
        ldp     x29, x30, [sp], #16             ; 16-byte Folded Reload
        ret
        .loh AdrpLdr    Lloh0, Lloh1
        .cfi_endproc

Note that TLS resolver call is not signed.

And indeed, there are no ptrauth-calls attribute:

define noundef range(i32 -2147483647, -2147483648) i32 @_Z1fv() local_unnamed_addr #0 {
entry:
  %0 = tail call align 4 ptr @llvm.threadlocal.address.p0(ptr align 4 @_ZZ1fvE1j)
  %1 = load i32, ptr %0, align 4, !tbaa !5
  %inc = add nsw i32 %1, 1
  store i32 %inc, ptr %0, align 4, !tbaa !5
  ret i32 %inc
}

; Function Attrs: mustprogress nocallback nofree nosync nounwind speculatable willreturn memory(none)
declare nonnull ptr @llvm.threadlocal.address.p0(ptr nonnull) #1

attributes #0 = { mustprogress nofree norecurse nosync nounwind ssp willreturn memory(readwrite, argmem: none, inaccessiblemem: none) uwtable(sync) "aarch64-jump-table-hardening" "frame-pointer"="non-leaf" "no-tr
apping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="apple-m1" "target-features"="+aes,+altnzcv,+ccdp,+ccidx,+complxnum,+crc,+dit,+dotprod,+flagm,+fp-armv8,+fp16fml,+fptoint,+fullfp16,+jsconv,+lse,
+neon,+pauth,+perfmon,+predres,+ras,+rcpc,+rdm,+sb,+sha2,+sha3,+specrestrict,+ssbs,+v8.1a,+v8.2a,+v8.3a,+v8.4a,+v8a,+zcm,+zcz" }
attributes #1 = { mustprogress nocallback nofree nosync nounwind speculatable willreturn memory(none) }

Explicit options seems to be not accepted by driver:

clang++ tls.cpp -S  -O1 -target arm64e-apple-darwin -S -fptrauth-calls
clang++: error: unsupported option '-fptrauth-calls' for target 'arm64e-apple-darwin'

[llvmbot]

@llvm/issue-subscribers-clang-driver

Author: Anton Korobeynikov (asl)

Consider the following code: ```c++ int f() { thread_local int j = 0; j++; return j; } ```

Running clang++ tls.cpp -S -O1 -target arm64e-apple-darwin yields:

Lloh0:
        adrp    x0, __ZZ1fvE1j@<!-- -->TLVPPAGE
Lloh1:
        ldr     x0, [x0, __ZZ1fvE1j@<!-- -->TLVPPAGEOFF]
        ldr     x8, [x0]
        blr     x8
        ldr     w8, [x0]
        add     w8, w8, #<!-- -->1
        str     w8, [x0]
        mov     x0, x8
        ldp     x29, x30, [sp], #<!-- -->16             ; 16-byte Folded Reload
        ret
        .loh AdrpLdr    Lloh0, Lloh1
        .cfi_endproc

Note that TLS resolver is not signed.

And indeed, there are no ptrauth-calls attribute:

define noundef range(i32 -2147483647, -2147483648) i32 @<!-- -->_Z1fv() local_unnamed_addr #<!-- -->0 {
entry:
  %0 = tail call align 4 ptr @<!-- -->llvm.threadlocal.address.p0(ptr align 4 @<!-- -->_ZZ1fvE1j)
  %1 = load i32, ptr %0, align 4, !tbaa !5
  %inc = add nsw i32 %1, 1
  store i32 %inc, ptr %0, align 4, !tbaa !5
  ret i32 %inc
}

; Function Attrs: mustprogress nocallback nofree nosync nounwind speculatable willreturn memory(none)
declare nonnull ptr @<!-- -->llvm.threadlocal.address.p0(ptr nonnull) #<!-- -->1

attributes #<!-- -->0 = { mustprogress nofree norecurse nosync nounwind ssp willreturn memory(readwrite, argmem: none, inaccessiblemem: none) uwtable(sync) "aarch64-jump-table-hardening" "frame-pointer"="non-leaf" "no-tr
apping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="apple-m1" "target-features"="+aes,+altnzcv,+ccdp,+ccidx,+complxnum,+crc,+dit,+dotprod,+flagm,+fp-armv8,+fp16fml,+fptoint,+fullfp16,+jsconv,+lse,
+neon,+pauth,+perfmon,+predres,+ras,+rcpc,+rdm,+sb,+sha2,+sha3,+specrestrict,+ssbs,+v8.1a,+v8.2a,+v8.3a,+v8.4a,+v8a,+zcm,+zcz" }
attributes #<!-- -->1 = { mustprogress nocallback nofree nosync nounwind speculatable willreturn memory(none) }

Explicit options seems to be not accepted by driver:

clang++ tls.cpp -S  -O1 -target arm64e-apple-darwin -S -fptrauth-calls
clang++: error: unsupported option '-fptrauth-calls' for target 'arm64e-apple-darwin'

[asl]

Tagging @ahmedbougacha @ojhunt

FWIW, ELF platforms are fine.

[asl]

And for the record, running Apple clang with exactly same of options yields:

; Function Attrs: mustprogress nofree norecurse nosync nounwind ssp willreturn memory(readwrite, argmem: none, inaccessiblemem: none) uwtable(sync)
define range(i32 -2147483647, -2147483648) i32 @_Z1fv() local_unnamed_addr #0 {
  %1 = tail call align 4 ptr @llvm.threadlocal.address.p0(ptr align 4 @_ZZ1fvE1j)
  %2 = load i32, ptr %1, align 4, !tbaa !9
  %3 = add nsw i32 %2, 1
  store i32 %3, ptr %1, align 4, !tbaa !9
  ret i32 %3
}

; Function Attrs: mustprogress nocallback nofree nosync nounwind speculatable willreturn memory(none)
declare nonnull ptr @llvm.threadlocal.address.p0(ptr nonnull) #1

attributes #0 = { mustprogress nofree norecurse nosync nounwind ssp willreturn memory(readwrite, argmem: none, inaccessiblemem: none) uwtable(sync) "frame-pointer"="non-leaf" "no-trapping-math"="true" "probe-stac
k"="__chkstk_darwin" "ptrauth-auth-traps" "ptrauth-calls" "ptrauth-indirect-gotos" "ptrauth-returns" "stack-protector-buffer-size"="8" "target-cpu"="apple-m1" "target-features"="+aes,+altnzcv,+bti,+ccdp,+ccidx,+c
omplxnum,+crc,+dit,+dotprod,+flagm,+fp-armv8,+fp16fml,+fptoint,+fullfp16,+jsconv,+lse,+neon,+pauth,+perfmon,+predres,+ras,+rcpc,+rdm,+sb,+sha2,+sha3,+specrestrict,+ssbs,+v8.1a,+v8.2a,+v8.3a,+v8.4a,+v8.5a,+v8a,+zc
m,+zcz" }
attributes #1 = { mustprogress nocallback nofree nosync nounwind speculatable willreturn memory(none) }

[asl]

False alarm, I'm having multiple of different clang / LLVM trees around from different projects. LLVM mainline (itself!) seems to be fine.