Restricts the final instruction in each function to be diverted. (#522)

Author: Lichtso

src/verifier.rs

@@ -243,7 +243,7 @@ impl Verifier for RequisiteVerifier {
                 function_range.end = *function_iter.peek().unwrap_or(&program_range.end);
                 let insn = ebpf::get_insn(prog, function_range.end.saturating_sub(1));
                 match insn.opc {
-                    ebpf::JA | ebpf::CALL_IMM | ebpf::CALL_REG | ebpf::EXIT => {},
+                    ebpf::JA | ebpf::EXIT => {},
                     _ => return Err(VerifierError::InvalidFunction(
                         function_range.end.saturating_sub(1),
                     )),

tests/execution.rs

@@ -2639,16 +2639,17 @@ fn test_tight_infinite_recursion_callx() {
         "
         mov64 r8, 0x1
         lsh64 r8, 0x20
-        or64 r8, 0x20
+        or64 r8, 0x28
         call function_foo
+        exit
         function_foo:
         mov64 r3, 0x41414141
         callx r8
         exit",
         [],
         (),
         TestContextObject::new(8),
-        ProgramResult::Err(Box::new(EbpfError::ExceededMaxInstructions(35))),
+        ProgramResult::Err(Box::new(EbpfError::ExceededMaxInstructions(36))),
     );
 }
 
@@ -2674,7 +2675,7 @@ fn test_err_instruction_count_syscall_capped() {
     test_interpreter_and_jit_asm!(
         "
         mov64 r2, 0x5
-        call 0
+        syscall bpf_syscall_string
         mov64 r0, 0x0
         exit",
         [72, 101, 108, 108, 111],
@@ -2787,41 +2788,44 @@ fn test_err_exit_capped() {
         "
         mov64 r1, 0x1
         lsh64 r1, 0x20
-        or64 r1, 0x20
+        or64 r1, 0x28
         callx r1
+        exit
         function_foo:
         exit
         ",
         [],
         (),
         TestContextObject::new(5),
-        ProgramResult::Err(Box::new(EbpfError::ExceededMaxInstructions(34))),
+        ProgramResult::Err(Box::new(EbpfError::ExceededMaxInstructions(35))),
     );
     test_interpreter_and_jit_asm!(
         "
         mov64 r1, 0x1
         lsh64 r1, 0x20
-        or64 r1, 0x20
+        or64 r1, 0x28
         callx r1
+        exit
         function_foo:
         mov r0, r0
         exit
         ",
         [],
         (),
         TestContextObject::new(6),
-        ProgramResult::Err(Box::new(EbpfError::ExceededMaxInstructions(35))),
+        ProgramResult::Err(Box::new(EbpfError::ExceededMaxInstructions(36))),
     );
     test_interpreter_and_jit_asm!(
         "
-        call 0
+        call 1
+        exit
         mov r0, r0
         exit
         ",
         [],
         (),
         TestContextObject::new(3),
-        ProgramResult::Err(Box::new(EbpfError::ExceededMaxInstructions(32))),
+        ProgramResult::Err(Box::new(EbpfError::ExceededMaxInstructions(33))),
     );
 }