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use binaryninja::{
binary_view::BinaryView,
function::Function,
low_level_il::{
expression::{ExpressionHandler as _, LowLevelILExpressionKind},
function::{LowLevelILFunction, Mutable, NonSSA, SSA},
instruction::{InstructionHandler as _, LowLevelILInstruction, LowLevelILInstructionKind},
operation::{CallSsa, Operation},
},
variable::PossibleValueSet,
workflow::AnalysisContext,
};
use crate::{
error::ILLevel,
metadata::{GlobalState, Selector},
Error,
};
mod adjust_call_type;
mod rewrite_to_direct_call;
// Apply all transformations that are specific to calls to `objc_msgSend` and `objc_msgSendSuper2`
// At present these are:
// 1. Call type adjustments
// 2. Rewriting to direct calls, if enabled.
pub fn process(ac: &AnalysisContext) -> Result<(), Error> {
let bv = ac.view();
if GlobalState::should_ignore_view(&bv) {
return Ok(());
}
let func_start = ac.function().start();
let Some(llil) = (unsafe { ac.llil_function() }) else {
return Err(Error::MissingIL {
level: ILLevel::Low,
func_start,
});
};
let Some(ssa) = llil.ssa_form() else {
return Err(Error::MissingSsaForm {
level: ILLevel::Low,
func_start,
});
};
let func = ac.function();
let mut function_changed = false;
for block in ssa.basic_blocks().iter() {
for insn in block.iter() {
match process_instruction(&bv, &func, &llil, &ssa, &insn) {
Ok(true) => function_changed = true,
Ok(_) => {}
Err(err) => {
tracing::error!(
"Error processing instruction at {:#x}: {}",
insn.address(),
err
);
continue;
}
}
}
}
if function_changed {
// Regenerate SSA form after modifications
llil.generate_ssa_form();
}
Ok(())
}
// Process a single instruction, looking for calls to `objc_msgSend` or `objc_msgSendSuper2`
// Returns `Ok(false)` if the instruction is not a relevant call or if the function was not
// modified. Returns `Ok(true)` to indicate that the function was modified.
fn process_instruction(
bv: &BinaryView,
func: &Function,
llil: &LowLevelILFunction<Mutable, NonSSA>,
ssa: &LowLevelILFunction<Mutable, SSA>,
insn: &LowLevelILInstruction<Mutable, SSA>,
) -> Result<bool, &'static str> {
let call_op = match insn.kind() {
LowLevelILInstructionKind::CallSsa(op) => op,
LowLevelILInstructionKind::TailCallSsa(op) => op,
_ => return Ok(false),
};
let target = call_op.target();
let target_values = target.possible_values();
// Check if the target is a constant pointer to objc_msgSend
let call_target = match target_values {
PossibleValueSet::ConstantValue { value }
| PossibleValueSet::ConstantPointerValue { value }
| PossibleValueSet::ImportedAddressValue { value } => value as u64,
_ => return Ok(false),
};
let Some(message_send_type) = call_target_type(bv, call_target) else {
return Ok(false);
};
let Some(selector) = selector_from_call(bv, ssa, &call_op) else {
return Ok(false);
};
let mut function_changed = false;
if adjust_call_type::process_call(bv, func, ssa, insn, &selector, message_send_type).is_ok() {
function_changed = true;
}
if rewrite_to_direct_call::process_call(bv, llil, insn, &selector, message_send_type).is_ok() {
function_changed = true;
}
Ok(function_changed)
}
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum MessageSendType {
Normal,
Super,
}
fn call_target_type(bv: &BinaryView, call_target: u64) -> Option<MessageSendType> {
let name = bv
.symbol_by_address(call_target)
.map(|s| s.raw_name().to_string_lossy().into_owned())?;
// Strip the `j_` prefix that the shared cache adds to the names of stub functions
let name = name.strip_prefix("j_").unwrap_or(&name);
if name == "_objc_msgSend" {
Some(MessageSendType::Normal)
} else if name == "_objc_msgSendSuper" || name == "_objc_msgSendSuper2" {
Some(MessageSendType::Super)
} else {
None
}
}
fn selector_from_call(
bv: &BinaryView,
ssa: &LowLevelILFunction<Mutable, SSA>,
call_op: &Operation<Mutable, SSA, CallSsa>,
) -> Option<Selector> {
let LowLevelILExpressionKind::CallParamSsa(params) = &call_op.param_expr().kind() else {
return None;
};
let param_exprs = params.param_exprs();
if param_exprs.is_empty() {
return None;
}
let param_exprs =
if let LowLevelILExpressionKind::SeparateParamListSsa(params) = ¶m_exprs[0].kind() {
params.param_exprs()
} else {
param_exprs
};
let LowLevelILExpressionKind::RegSsa(reg) = param_exprs.get(1)?.kind() else {
return None;
};
let raw_selector = ssa.get_ssa_register_value(reg.source_reg())?.value as u64;
if raw_selector == 0 {
return None;
}
Selector::from_address(bv, raw_selector).ok()
}
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