Removes EbpfVm::stack_pointer.

src/jit.rs

@@ -255,15 +255,14 @@ struct Jump {
 enum RuntimeEnvironmentSlot {
     HostStackPointer = 0,
     CallDepth = 1,
-    StackPointer = 2,
-    ContextObjectPointer = 3,
-    PreviousInstructionMeter = 4,
-    DueInsnCount = 5,
-    StopwatchNumerator = 6,
-    StopwatchDenominator = 7,
-    Registers = 8,
-    ProgramResult = 20,
-    MemoryMapping = 28,
+    ContextObjectPointer = 2,
+    PreviousInstructionMeter = 3,
+    DueInsnCount = 4,
+    StopwatchNumerator = 5,
+    StopwatchDenominator = 6,
+    Registers = 7,
+    ProgramResult = 19,
+    MemoryMapping = 27,
 }
 
 /* Explanation of the Instruction Meter
@@ -1747,7 +1746,6 @@ mod tests {
 
         check_slot!(env, host_stack_pointer, HostStackPointer);
         check_slot!(env, call_depth, CallDepth);
-        check_slot!(env, stack_pointer, StackPointer);
         check_slot!(env, context_object_pointer, ContextObjectPointer);
         check_slot!(env, previous_instruction_meter, PreviousInstructionMeter);
         check_slot!(env, due_insn_count, DueInsnCount);

src/vm.rs

@@ -287,13 +287,6 @@ pub struct EbpfVm<'a, C: ContextObject> {
     /// Incremented on calls and decremented on exits. It's used to enforce
     /// config.max_call_depth and to know when to terminate execution.
     pub call_depth: u64,
-    /// Guest stack pointer (r11).
-    ///
-    /// The stack pointer isn't exposed as an actual register. Only sub and add
-    /// instructions (typically generated by the LLVM backend) are allowed to
-    /// access it when sbpf_version.dynamic_stack_frames()=true. Its value is only
-    /// stored here and therefore the register is not tracked in REGISTER_MAP.
-    pub stack_pointer: u64,
     /// Pointer to ContextObject
     pub context_object_pointer: &'a mut C,
     /// Last return value of instruction_meter.get_remaining()
@@ -329,7 +322,8 @@ impl<'a, C: ContextObject> EbpfVm<'a, C> {
         stack_len: usize,
     ) -> Self {
         let config = loader.get_config();
-        let stack_pointer =
+        let mut registers = [0u64; 12];
+        registers[ebpf::FRAME_PTR_REG] =
             ebpf::MM_STACK_START.saturating_add(if sbpf_version.dynamic_stack_frames() {
                 // the stack is fully descending, frames start as empty and change size anytime r11 is modified
                 stack_len
@@ -343,13 +337,12 @@ impl<'a, C: ContextObject> EbpfVm<'a, C> {
         EbpfVm {
             host_stack_pointer: std::ptr::null_mut(),
             call_depth: 0,
-            stack_pointer,
             context_object_pointer: context_object,
             previous_instruction_meter: 0,
             due_insn_count: 0,
             stopwatch_numerator: 0,
             stopwatch_denominator: 0,
-            registers: [0u64; 12],
+            registers,
             program_result: ProgramResult::Ok(0),
             memory_mapping,
             call_frames: vec![CallFrame::default(); config.max_call_depth],
@@ -368,9 +361,7 @@ impl<'a, C: ContextObject> EbpfVm<'a, C> {
         interpreted: bool,
     ) -> (u64, ProgramResult) {
         debug_assert!(Arc::ptr_eq(&self.loader, executable.get_loader()));
-        // R1 points to beginning of input memory, R10 to the stack of the first frame, R11 is the pc (hidden)
         self.registers[1] = ebpf::MM_INPUT_START;
-        self.registers[ebpf::FRAME_PTR_REG] = self.stack_pointer;
         self.registers[11] = executable.get_entrypoint_instruction_offset() as u64;
         let config = executable.get_config();
         let initial_insn_count = if config.enable_instruction_meter {