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-rw-r--r--test/long_mode/mod.rs30
1 files changed, 30 insertions, 0 deletions
diff --git a/test/long_mode/mod.rs b/test/long_mode/mod.rs
index 1e8a72e..25a303c 100644
--- a/test/long_mode/mod.rs
+++ b/test/long_mode/mod.rs
@@ -3456,6 +3456,36 @@ fn from_reports() {
test_display(&[0xf3, 0x0f, 0x1e, 0x0f], "nop dword [rdi], ecx");
}
+/// the first four single byte registers (`al`, `cl`, `dl`, `bl`) can be described as either the
+/// first four registers of the old `B` bank (`al..bh`) or the first four registers of the new `rB`
+/// bank, used when `rex.w` is present on the instruction. `RegSpec` relies on the bank matching to
+/// compare equality, as well as for `Hash` and `Ord` to work correctly, so having two spellings of
+/// the register `al` (and friends) can be a correctness issue for dependent code.
+#[test]
+fn register_synonyms_use_old_bank() {
+ // a few instructions where adding a rex.w prefix would yield a synonymous byte-size register
+ let cases: &'static [&'static [u8]] = &[
+ &[0x30, 0x00],
+ &[0x30, 0xc1],
+ &[0x0f, 0xb6, 0xc0],
+ &[0x0f, 0xbe, 0xc0],
+ &[0xb2, 0xff], // from `does_not_decode_invalid_registers` fuzz target 🎉
+ ];
+
+ for case in cases.iter() {
+ let mut case_with_rexw: Vec<u8> = vec![0x48];
+ case_with_rexw.extend_from_slice(case);
+
+ let mut reader = yaxpeax_arch::U8Reader::new(case);
+ let no_rexw = InstDecoder::default().decode(&mut reader).expect("can disassemble test instruction");
+
+ let mut reader = yaxpeax_arch::U8Reader::new(case);
+ let with_rexw = InstDecoder::default().decode(&mut reader).expect("can disassemble test instruction");
+
+ assert_eq!(no_rexw, with_rexw);
+ }
+}
+
mod reg_specs {
use yaxpeax_x86::long_mode::RegSpec;