minecraft-pi-reborn/libreborn/src/patch/instruction.cpp

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2024-02-12 05:44:38 +00:00
#include <libreborn/libreborn.h>
#include "patch-internal.h"
// Generate A BL Instruction
#define INSTRUCTION_RANGE 32000000
static uint64_t nice_diff_64(uint64_t a, uint64_t b) {
if (a > b) {
return a - b;
} else {
return b - a;
}
}
uint32_t generate_bl_instruction(void *from, void *to, int use_b_instruction) {
// Check Instruction Range
if (nice_diff_64((uint64_t) to, (uint64_t) from) > INSTRUCTION_RANGE) {
IMPOSSIBLE();
}
// Create New Instruction
uint32_t instruction;
unsigned char *instruction_array = (unsigned char *) &instruction;
instruction_array[3] = use_b_instruction ? B_INSTRUCTION : BL_INSTRUCTION;
// Determine PC
unsigned char *pc = ((unsigned char *) from) + 8;
int32_t offset = (int32_t) to - (int32_t) pc;
int32_t target = offset >> 2;
// Set Instruction Offset
unsigned char *target_array = (unsigned char *) &target;
instruction_array[0] = target_array[0];
instruction_array[1] = target_array[1];
instruction_array[2] = target_array[2];
// Return
return instruction;
}
// Extract Target Address From B(L) Instruction
void *extract_from_bl_instruction(unsigned char *from) {
// Calculate PC
unsigned char *pc = ((unsigned char *) from) + 8;
// Extract Offset From Instruction
int32_t target = *(int32_t *) from;
target = (target << 8) >> 8;
int32_t offset = target << 2;
// Add PC To Offset
return (void *) (pc + offset);
}