MCInstPrinter.c

/* Capstone Disassembly Engine */
/* By Rot127 <unisono@quyllur.org>, 2023 */

#include "MCInstPrinter.h"
#include "cs_priv.h"
#include <capstone/platform.h>

extern bool ARM_getFeatureBits(unsigned int mode, unsigned int feature);
extern bool PPC_getFeatureBits(unsigned int mode, unsigned int feature);
extern bool AArch64_getFeatureBits(unsigned int mode, unsigned int feature);

static bool testFeatureBits(const MCInst *MI, uint32_t Value)
{
	assert(MI && MI->csh);
	switch (MI->csh->arch) {
	default:
		assert(0 && "Not implemented for current arch.");
		return false;
#ifdef CAPSTONE_HAS_ARM
	case CS_ARCH_ARM:
		return ARM_getFeatureBits(MI->csh->mode, Value);
#endif
#ifdef CAPSTONE_HAS_POWERPC
	case CS_ARCH_PPC:
		return PPC_getFeatureBits(MI->csh->mode, Value);
#endif
#ifdef CAPSTONE_HAS_AARCH64
	case CS_ARCH_AARCH64:
		return AArch64_getFeatureBits(MI->csh->mode, Value);
#endif
	}
}

static bool matchAliasCondition(MCInst *MI, const MCRegisterInfo *MRI,
								unsigned *OpIdx, const AliasMatchingData *M,
								const AliasPatternCond *C,
								bool *OrPredicateResult)
{
	// Feature tests are special, they don't consume operands.
	if (C->Kind == AliasPatternCond_K_Feature)
		return testFeatureBits(MI, C->Value);
	if (C->Kind == AliasPatternCond_K_NegFeature)
		return !testFeatureBits(MI, C->Value);
	// For feature tests where just one feature is required in a list, set the
	// predicate result bit to whether the expression will return true, and only
	// return the real result at the end of list marker.
	if (C->Kind == AliasPatternCond_K_OrFeature) {
		*OrPredicateResult |= testFeatureBits(MI, C->Value);
		return true;
	}
	if (C->Kind == AliasPatternCond_K_OrNegFeature) {
		*OrPredicateResult |= !(testFeatureBits(MI, C->Value));
		return true;
	}
	if (C->Kind == AliasPatternCond_K_EndOrFeatures) {
		bool Res = *OrPredicateResult;
		*OrPredicateResult = false;
		return Res;
	}

	// Get and consume an operand.
	MCOperand *Opnd = MCInst_getOperand(MI, *OpIdx);
	++(*OpIdx);

	// Check the specific condition for the operand.
	switch (C->Kind) {
	default:
		assert(0 && "invalid kind");
	case AliasPatternCond_K_Imm:
		// Operand must be a specific immediate.
		return MCOperand_isImm(Opnd) &&
			   MCOperand_getImm(Opnd) == (int32_t)C->Value;
	case AliasPatternCond_K_Reg:
		// Operand must be a specific register.
		return MCOperand_isReg(Opnd) && MCOperand_getReg(Opnd) == C->Value;
	case AliasPatternCond_K_TiedReg:
		// Operand must match the register of another operand.
		return MCOperand_isReg(Opnd) &&
			   MCOperand_getReg(Opnd) ==
				   MCOperand_getReg(MCInst_getOperand(MI, C->Value));
	case AliasPatternCond_K_RegClass:
		// Operand must be a register in this class. Value is a register class
		// id.
		return MCOperand_isReg(Opnd) &&
			   MCRegisterClass_contains(
				   MCRegisterInfo_getRegClass(MRI, C->Value),
				   MCOperand_getReg(Opnd));
	case AliasPatternCond_K_Custom:
		// Operand must match some custom criteria.
		assert(M->ValidateMCOperand && "A custom validator should be set but isn't.");
		return M->ValidateMCOperand(Opnd, C->Value);
	case AliasPatternCond_K_Ignore:
		// Operand can be anything.
		return true;
	case AliasPatternCond_K_Feature:
	case AliasPatternCond_K_NegFeature:
	case AliasPatternCond_K_OrFeature:
	case AliasPatternCond_K_OrNegFeature:
	case AliasPatternCond_K_EndOrFeatures:
		assert(0 && "handled earlier");
	}
	return false;
}

/// Check if PatternsForOpcode is all zero.
static inline bool validOpToPatter(const PatternsForOpcode *P)
{
	return !(P->Opcode == 0 && P->PatternStart == 0 && P->NumPatterns == 0);
}

const char *matchAliasPatterns(MCInst *MI, const AliasMatchingData *M)
{
	// TODO Rewrite to C

	// auto It = lower_bound(M.OpToPatterns, MI->getOpcode(),
	//                       [](const PatternsForOpcode &L, unsigned Opcode) {
	//                         return L.Opcode < Opcode;
	//                       });
	// if (It == M.OpToPatterns.end() || It->Opcode != MI->getOpcode())
	//   return nullptr;

	// Binary search by opcode. Return false if there are no aliases for this
	// opcode.
	unsigned MIOpcode = MI->Opcode;
	size_t i = 0;
	uint32_t PatternOpcode = M->OpToPatterns[i].Opcode;
	while (PatternOpcode < MIOpcode && validOpToPatter(&M->OpToPatterns[i]))
		PatternOpcode = M->OpToPatterns[++i].Opcode;
	if (PatternOpcode != MI->Opcode || !validOpToPatter(&M->OpToPatterns[i]))
		return NULL;

	// // Try all patterns for this opcode.
	uint32_t AsmStrOffset = ~0U;
	const AliasPattern *Patterns = M->Patterns + M->OpToPatterns[i].PatternStart;
	for (const AliasPattern *P = Patterns;
		P != Patterns + M->OpToPatterns[i].NumPatterns; ++P) {
		// Check operand count first.
		if (MCInst_getNumOperands(MI) != P->NumOperands)
			return NULL;

		// Test all conditions for this pattern.
		const AliasPatternCond *Conds = M->PatternConds + P->AliasCondStart;
		unsigned OpIdx = 0;
		bool OrPredicateResult = false;
		bool allMatch = true;
		for (const AliasPatternCond *C = Conds; C != Conds + P->NumConds; ++C) {
			if (!matchAliasCondition(MI, MI->MRI, &OpIdx, M, C, &OrPredicateResult)) {
				allMatch = false;
				break;
			}
		}
		if (allMatch) {
			AsmStrOffset = P->AsmStrOffset;
			break;
		}
	}
	// If no alias matched, don't print an alias.
	if (AsmStrOffset == ~0U)
		return NULL;

	// Go to offset AsmStrOffset and use the null terminated string there. The
	// offset should point to the beginning of an alias string, so it should
	// either be zero or be preceded by a null byte.
	return M->AsmStrings + AsmStrOffset;
}

// TODO Add functionality to toggle the flag.
bool getUseMarkup(void) { return false; }

/// Utility functions to make adding mark ups simpler.
const char *markup(const char *s)
{
	static const char *no_markup = "";
	if (getUseMarkup())
		return s;
	else
		return no_markup;
}

// binary search for encoding in IndexType array
// return -1 if not found, or index if found
unsigned int binsearch_IndexTypeEncoding(const struct IndexType *index, size_t size, uint16_t encoding)
{
	// binary searching since the index is sorted in encoding order
	size_t left, right, m;

	right = size - 1;

	if (encoding < index[0].encoding || encoding > index[right].encoding)
		// not found
		return -1;

	left = 0;

	while(left <= right) {
		m = (left + right) / 2;
		if (encoding == index[m].encoding) {
			// LLVM actually uses lower_bound for the index table search
			// Here we need to check if a previous entry is of the same encoding
			// and return the first one.
			while (m > 0 && encoding == index[m - 1].encoding)
				--m;
			return m;
		}

		if (encoding < index[m].encoding)
			right = m - 1;
		else
			left = m + 1;
	}

	// not found
	return -1;
}

// binary search for encoding in IndexTypeStr array
// return -1 if not found, or index if found
unsigned int binsearch_IndexTypeStrEncoding(const struct IndexTypeStr *index, size_t size, const char *name)
{
	// binary searching since the index is sorted in encoding order
	size_t left, right, m;

	right = size - 1;

	size_t str_left_cmp = strcmp(name, index[0].name);
	size_t str_right_cmp = strcmp(name, index[right].name);
	if (str_left_cmp < 0 || str_right_cmp > 0)
		// not found
		return -1;

	left = 0;

	while(left <= right) {
		m = (left + right) / 2;
		if (strcmp(name, index[m].name) == 0) {
			// LLVM actually uses lower_bound for the index table search
			// Here we need to check if a previous entry is of the same encoding
			// and return the first one.
			while (m > 0 && (strcmp(name, index[m - 1].name) == 0))
				--m;
			return m;
		}

		if (strcmp(name, index[m].name) < 0)
			right = m - 1;
		else
			left = m + 1;
	}

	// not found
	return -1;
}