[llvm-bugs] [Bug 46480] New: [AArch64] .note.gnu.property always generated for object file without code

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46480

            Bug ID: 46480
           Summary: [AArch64] .note.gnu.property always generated for
                    object file without code
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: keescook at chromium.org
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org,
                    neeilans at live.com, richard-llvm at metafoo.co.uk

The .note.gnu.property is generated even when -mbranch-protection=none is used,
on a source file that only has data (no code).


$ cat foo.c
int global = 5;
$ clang --target=aarch64-linux-gnu -c -o foo.o foo.c
$ readelf -n foo.o

Displaying notes found in: .note.gnu.property
  Owner                Data size        Description
  GNU                  0x00000010       NT_GNU_PROPERTY_TYPE_0
      Properties: AArch64 feature: BTI, PAC
$ clang --target=aarch64-linux-gnu -mbranch-protection=none -c -o foo.o foo.c
$ readelf -n foo.o

Displaying notes found in: .note.gnu.property
  Owner                Data size        Description
  GNU                  0x00000010       NT_GNU_PROPERTY_TYPE_0
      Properties: AArch64 feature: BTI, PAC
$ aarch64-linux-gnu-gcc -c -o foo.o foo.c
$ readelf -n foo.o
$ aarch64-linux-gnu-gcc -mbranch-protection=bti -c -o foo.o foo.c
$ readelf -n foo.o

Displaying notes found in: .note.gnu.property
  Owner                Data size        Description
  GNU                  0x00000010       NT_GNU_PROPERTY_TYPE_0
      Properties: AArch64 feature: BTI



$ cat bar.c
int code(void) { return 5; }
$ clang --target=aarch64-linux-gnu -c -o bar.o bar.c
$ readelf -n bar.o
$ clang --target=aarch64-linux-gnu -mbranch-protection=bti -c -o bar.o bar.c
$ readelf -n bar.o

Displaying notes found in: .note.gnu.property
  Owner                Data size        Description
  GNU                  0x00000010       NT_GNU_PROPERTY_TYPE_0
      Properties: AArch64 feature: BTI

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