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Improve cheats documentation

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This commit is contained in:
Robin Jones 2025-02-21 22:50:56 +00:00
parent 63747e148f
commit 2452bc0373
1 changed files with 52 additions and 11 deletions
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63
src/boot/cheats.c
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@ -1,5 +1,10 @@
#include <libdragon.h>
/**
* @file cheats.c
* @brief Cheat Engine Implementation
* @ingroup boot
*/
#include <libdragon.h>
#include "boot_io.h"
#include "cheats.h"
#include "vr4300_asm.h"
@ -21,22 +26,25 @@
#define ENGINE_TEMPORARY_ADDRESS (PATCHER_ADDRESS + 0x10000)
#define DEFAULT_ENGINE_ADDRESS (0x807C5C00)
/** @brief Cheat structure */
typedef struct {
uint8_t type;
uint32_t address;
uint16_t value;
uint8_t type; /**< Cheat type */
uint32_t address; /**< Cheat address */
uint16_t value; /**< Cheat value */
} cheat_t;
/** @brief Cheat entry structure */
typedef struct {
cheat_t main;
cheat_t sub;
cheat_t main; /**< Main cheat */
cheat_t sub; /**< Sub cheat */
} cheat_entry_t;
/** @brief Special cheat types enumeration */
typedef enum {
SPECIAL_DISABLE_EXPANSION_PAK = 0xEE,
SPECIAL_WRITE_BYTE_ON_BOOT = 0xF0,
SPECIAL_WRITE_SHORT_ON_BOOT = 0xF1,
SPECIAL_SET_STORE_LOCATION = 0xFF,
SPECIAL_DISABLE_EXPANSION_PAK = 0xEE, /**< Disable Expansion Pak */
SPECIAL_WRITE_BYTE_ON_BOOT = 0xF0, /**< Write byte on boot */
SPECIAL_WRITE_SHORT_ON_BOOT = 0xF1, /**< Write short on boot */
SPECIAL_SET_STORE_LOCATION = 0xFF, /**< Set store location */
} cheat_type_special_t;
#define IS_WIDTH_16(t) ((t) & (1 << 0))
@ -49,6 +57,13 @@ typedef enum {
#define IS_DOUBLE_ENTRY(t) (IS_TYPE_CONDITIONAL(t) || IS_TYPE_REPEATER(t))
/**
* @brief Patch the IPL3 with the cheat engine.
*
* @param cic_type The CIC type.
* @param target The target address.
* @return true if successful, false otherwise.
*/
static bool cheats_patch_ipl3 (cic_type_t cic_type, io32_t *target) {
uint32_t patch_offset = 0;
uint32_t j_instruction = I_J((uint32_t)(target));
@ -92,6 +107,13 @@ static bool cheats_patch_ipl3 (cic_type_t cic_type, io32_t *target) {
return false;
}
/**
* @brief Get the next cheat entry from the cheat list.
*
* @param cheat_list Pointer to the cheat list.
* @param cheat Pointer to the cheat entry structure.
* @return true if successful, false otherwise.
*/
static bool cheats_get_next (uint32_t **cheat_list, cheat_entry_t *cheat) {
cheat_t *c = &cheat->main;
cheat->sub.type = 0;
@ -119,6 +141,12 @@ static bool cheats_get_next (uint32_t **cheat_list, cheat_entry_t *cheat) {
return true;
}
/**
* @brief Get the engine address from the cheat list.
*
* @param cheat_list Pointer to the cheat list.
* @return io32_t* The engine address.
*/
static io32_t *cheats_get_engine_address (uint32_t *cheat_list) {
cheat_entry_t cheat;
while (cheats_get_next(&cheat_list, &cheat)) {
@ -129,11 +157,24 @@ static io32_t *cheats_get_engine_address (uint32_t *cheat_list) {
return (io32_t *)(DEFAULT_ENGINE_ADDRESS);
}
/**
* @brief Update the cache for the specified memory range.
*
* @param start The start address.
* @param end The end address.
*/
static void cheats_update_cache (volatile void *start, volatile void *end) {
data_cache_hit_writeback(start, (end - start));
inst_cache_hit_invalidate(start, (end - start));
}
/**
* @brief Install the cheat engine.
*
* @param cic_type The CIC type.
* @param cheat_list Pointer to the cheat list.
* @return true if successful, false otherwise.
*/
bool cheats_install (cic_type_t cic_type, uint32_t *cheat_list) {
if (!cheat_list) {
return false;
@ -165,7 +206,7 @@ bool cheats_install (cic_type_t cic_type, uint32_t *cheat_list) {
*engine_p++ = I_BNEL(REG_K1, REG_ZERO, 1);
*engine_p++ = I_MTC0(REG_ZERO, C0_REG_WATCH_LO);
// Check if watch exception ocurred, if yes then proceed to relocate the game exception handler
// Check if watch exception occurred, if yes then proceed to relocate the game exception handler
*engine_p++ = I_ANDI(REG_K0, REG_K0, CAUSE_EXC_CODE_MASK);
*engine_p++ = I_ORI(REG_K1, REG_ZERO, CAUSE_EXC_CODE_WATCH);
*engine_p++ = I_BNE(REG_K0, REG_K1, 15); // Skips to after the 'eret' instruction