chore: add missing verifier tests and update docs (#612)

* chore: add missing verifier tests for lddw and callx

* chore: clarify length validation and that hor64 is not available in sbpfv1

* run test on both sbpf versions

doc/bytecode.md

@@ -293,7 +293,7 @@ Verification
 ------------
 
 ### all
-- The bytecode must be divisible by the instruction slot size (64 bits / 8 bytes)
+- The length of the bytecode must be evenly divisible by the instruction slot size (64 bits or 8 bytes)
 - The bytecode must contain at least one instruction
 - `lddw` (opcode `0x18`) is two slots long and must be followed by a slot with opcode `0x00`
 - Immediate values of quotient and remainder instructions must be imm ≠ 0
@@ -310,6 +310,7 @@ Verification
 ### until v2
 - Opcodes from the product / quotient / remainder instruction class are forbiden
 - `le` is allowed
+- `hor64` is forbidden
 - `callx` source register is encoded in the imm field
 - The targets of `call` instructions is checked at runtime not verification time
 - The offset of jump instructions must be limited to the range of the bytecode

tests/verifier.rs

@@ -138,6 +138,7 @@ fn test_verifier_err_endian_size() {
 #[should_panic(expected = "IncompleteLDDW(0)")]
 fn test_verifier_err_incomplete_lddw() {
     // Note: ubpf has test-err-incomplete-lddw2, which is the same
+    // lddw r0, 0x55667788
     let prog = &[
         0x18, 0x00, 0x00, 0x00, 0x88, 0x77, 0x66, 0x55, //
         0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, //
@@ -152,6 +153,28 @@ fn test_verifier_err_incomplete_lddw() {
     executable.verify::<RequisiteVerifier>().unwrap();
 }
 
+#[test]
+#[should_panic(expected = "LDDWCannotBeLast")]
+fn test_verifier_err_lddw_cannot_be_last() {
+    for highest_sbpf_version in [SBPFVersion::V1, SBPFVersion::V2] {
+        let prog = &[0x18, 0x00, 0x00, 0x00, 0x88, 0x77, 0x66, 0x55];
+        let executable = Executable::<TestContextObject>::from_text_bytes(
+            prog,
+            Arc::new(BuiltinProgram::new_loader(
+                Config {
+                    enabled_sbpf_versions: SBPFVersion::V1..=highest_sbpf_version,
+                    ..Config::default()
+                },
+                FunctionRegistry::default(),
+            )),
+            highest_sbpf_version,
+            FunctionRegistry::default(),
+        )
+        .unwrap();
+        executable.verify::<RequisiteVerifier>().unwrap();
+    }
+}
+
 #[test]
 fn test_verifier_err_invalid_reg_dst() {
     // r11 is disabled when sbpf_version.dynamic_stack_frames()=false, and only sub and add are
@@ -245,6 +268,28 @@ fn test_verifier_err_call_lddw() {
     executable.verify::<RequisiteVerifier>().unwrap();
 }
 
+#[test]
+#[should_panic(expected = "InvalidRegister(0)")]
+fn test_verifier_err_callx_cannot_use_r10() {
+    for highest_sbpf_version in [SBPFVersion::V1, SBPFVersion::V2] {
+        let executable = assemble::<TestContextObject>(
+            "
+        callx r10
+        exit
+        ",
+            Arc::new(BuiltinProgram::new_loader(
+                Config {
+                    enabled_sbpf_versions: SBPFVersion::V1..=highest_sbpf_version,
+                    ..Config::default()
+                },
+                FunctionRegistry::default(),
+            )),
+        )
+        .unwrap();
+        executable.verify::<RequisiteVerifier>().unwrap();
+    }
+}
+
 #[test]
 #[should_panic(expected = "InvalidFunction(0)")]
 fn test_verifier_err_function_fallthrough() {