ref: fa1fba7fd9f61197ee7b94a5aa4b949237c7ecbc
dir: /src/link/patch.c/
/*
* This file is part of RGBDS.
*
* Copyright (c) 2019, Eldred Habert and RGBDS contributors.
*
* SPDX-License-Identifier: MIT
*/
#include <stdlib.h>
#include <limits.h>
#include <string.h>
#include "link/patch.h"
#include "link/section.h"
#include "link/symbol.h"
#include "linkdefs.h"
#include "extern/err.h"
static int32_t asl(int32_t value, int32_t shiftamt); // Forward decl for below
static int32_t asr(int32_t value, int32_t shiftamt)
{
uint32_t uvalue = value;
// Get the easy cases out of the way
if (shiftamt == 0)
return value;
if (value == 0 || shiftamt <= -32)
return 0;
if (shiftamt > 31)
return (value < 0) ? -1 : 0;
if (shiftamt < 0)
return asl(value, -shiftamt);
if (value > 0)
return uvalue >> shiftamt;
{
// Calculate an OR mask for sign extension
// 1->0x80000000, 2->0xC0000000, ..., 31->0xFFFFFFFE
uint32_t shiftamt_high_bits = -((uint32_t)1 << (32 - shiftamt));
return (uvalue >> shiftamt) | shiftamt_high_bits;
}
}
static int32_t asl(int32_t value, int32_t shiftamt)
{
// Repeat the easy cases here to avoid INT_MIN funny business
if (shiftamt == 0)
return value;
if (value == 0 || shiftamt >= 32)
return 0;
if (shiftamt < -31)
return (value < 0) ? -1 : 0;
if (shiftamt < 0)
return asr(value, -shiftamt);
return (uint32_t)value << shiftamt;
}
/* This is an "empty"-type stack */
struct RPNStack {
int32_t *buf;
size_t size;
size_t capacity;
} stack;
static inline void initRPNStack(void)
{
stack.capacity = 64;
stack.buf = malloc(sizeof(*stack.buf) * stack.capacity);
if (!stack.buf)
err(1, "Failed to init RPN stack");
}
static inline void clearRPNStack(void)
{
stack.size = 0;
}
static void pushRPN(int32_t value)
{
if (stack.size >= stack.capacity) {
stack.capacity *= 2;
stack.buf =
realloc(stack.buf, sizeof(*stack.buf) * stack.capacity);
if (!stack.buf)
err(1, "Failed to resize RPN stack");
}
stack.buf[stack.size] = value;
stack.size++;
}
static int32_t popRPN(char const *fileName, int32_t lineNo)
{
if (stack.size == 0)
errx(1, "%s(%d): Internal error, RPN stack empty", fileName,
lineNo);
stack.size--;
return stack.buf[stack.size];
}
static inline void freeRPNStack(void)
{
free(stack.buf);
}
/* RPN operators */
static uint8_t getRPNByte(uint8_t const **expression, int32_t *size,
char const *fileName, int32_t lineNo)
{
if (!(*size)--)
errx(1, "%s(%d): RPN expression overread", fileName, lineNo);
return *(*expression)++;
}
/**
* Compute a patch's value from its RPN string.
* @param patch The patch to compute the value of
* @param section The section the patch is contained in
* @return The patch's value
*/
static int32_t computeRPNExpr(struct Patch const *patch,
struct Section const *section)
{
/* Small shortcut to avoid a lot of repetition */
#define popRPN() popRPN(patch->fileName, patch->lineNo)
uint8_t const *expression = patch->rpnExpression;
int32_t size = patch->rpnSize;
clearRPNStack();
while (size > 0) {
enum RPNCommand command = getRPNByte(&expression, &size,
patch->fileName,
patch->lineNo);
int32_t value;
/*
* Friendly reminder:
* Be VERY careful with two `popRPN` in the same expression.
* C does not guarantee order of evaluation of operands!!
* So, if there are two `popRPN` in the same expression, make
* sure the operation is commutative.
*/
switch (command) {
struct Symbol const *symbol;
char const *name;
struct Section const *sect;
case RPN_ADD:
value = popRPN() + popRPN();
break;
case RPN_SUB:
value = popRPN();
value = popRPN() - value;
break;
case RPN_MUL:
value = popRPN() * popRPN();
break;
case RPN_DIV:
value = popRPN();
value = popRPN() / value;
break;
case RPN_MOD:
value = popRPN();
value = popRPN() % value;
break;
case RPN_UNSUB:
value = -popRPN();
break;
case RPN_OR:
value = popRPN() | popRPN();
break;
case RPN_AND:
value = popRPN() & popRPN();
break;
case RPN_XOR:
value = popRPN() ^ popRPN();
break;
case RPN_UNNOT:
value = ~popRPN();
break;
case RPN_LOGAND:
value = popRPN();
value = popRPN() && value;
break;
case RPN_LOGOR:
value = popRPN();
value = popRPN() || value;
break;
case RPN_LOGUNNOT:
value = !popRPN();
break;
case RPN_LOGEQ:
value = popRPN() == popRPN();
break;
case RPN_LOGNE:
value = popRPN() != popRPN();
break;
case RPN_LOGGT:
value = popRPN();
value = popRPN() > value;
break;
case RPN_LOGLT:
value = popRPN();
value = popRPN() < value;
break;
case RPN_LOGGE:
value = popRPN();
value = popRPN() >= value;
break;
case RPN_LOGLE:
value = popRPN();
value = popRPN() <= value;
break;
case RPN_SHL:
value = popRPN();
value = asl(popRPN(), value);
break;
case RPN_SHR:
value = popRPN();
value = asr(popRPN(), value);
break;
case RPN_BANK_SYM:
value = 0;
for (uint8_t shift = 0; shift < 32; shift += 8)
value |= getRPNByte(&expression, &size,
patch->fileName,
patch->lineNo) << shift;
symbol = section->fileSymbols[value];
/* If the symbol is defined elsewhere... */
if (symbol->type == SYMTYPE_IMPORT) {
struct Symbol const *symbolDefinition =
sym_GetSymbol(symbol->name);
if (!symbolDefinition)
errx(1, "%s(%d): Unknown symbol \"%s\"",
patch->fileName, patch->lineNo,
symbol->name);
symbol = symbolDefinition;
}
value = symbol->section->bank;
break;
case RPN_BANK_SECT:
name = (char const *)expression;
while (getRPNByte(&expression, &size, patch->fileName,
patch->lineNo))
;
sect = sect_GetSection(name);
if (!sect)
errx(1, "%s(%d): Requested BANK() of section \"%s\", which was not found",
patch->fileName, patch->lineNo, name);
value = sect->bank;
break;
case RPN_BANK_SELF:
value = section->bank;
break;
case RPN_HRAM:
value = popRPN();
if (value < 0
|| (value > 0xFF && value < 0xFF00)
|| value > 0xFFFF)
errx(1, "%s(%d): Value %d is not in HRAM range",
patch->fileName, patch->lineNo, value);
value &= 0xFF;
break;
case RPN_RST:
value = popRPN();
/* Acceptable values are 0x00, 0x08, 0x10, ..., 0x38
* They can be easily checked with a bitmask
*/
if (value & ~0x38)
errx(1, "%s(%d): Value %d is not a RST vector",
patch->fileName, patch->lineNo, value);
value |= 0xC7;
break;
case RPN_CONST:
value = 0;
for (uint8_t shift = 0; shift < 32; shift += 8)
value |= getRPNByte(&expression, &size,
patch->fileName,
patch->lineNo) << shift;
break;
case RPN_SYM:
value = 0;
for (uint8_t shift = 0; shift < 32; shift += 8)
value |= getRPNByte(&expression, &size,
patch->fileName,
patch->lineNo) << shift;
symbol = section->fileSymbols[value];
/* If the symbol is defined elsewhere... */
if (symbol->type == SYMTYPE_IMPORT) {
struct Symbol const *symbolDefinition =
sym_GetSymbol(symbol->name);
if (!symbolDefinition)
errx(1, "%s(%d): Unknown symbol \"%s\"",
patch->fileName, patch->lineNo,
symbol->name);
symbol = symbolDefinition;
}
if (!strcmp(symbol->name, "@")) {
value = section->org + patch->offset;
} else {
value = symbol->value;
/* Symbols attached to sections have offsets */
if (symbol->section)
value += symbol->section->org;
}
break;
}
pushRPN(value);
}
if (stack.size > 1)
warnx("%s(%d): RPN stack has %lu entries on exit, not 1",
patch->fileName, patch->lineNo, stack.size);
return popRPN();
#undef popRPN
}
/**
* Applies all of a section's patches
* @param section The section to patch
* @param arg Ignored callback arg
*/
static void applyPatches(struct Section *section, void *arg)
{
(void)arg;
if (!sect_HasData(section->type))
return;
verbosePrint("Patching section \"%s\"...\n", section->name);
for (uint32_t patchID = 0; patchID < section->nbPatches; patchID++) {
struct Patch *patch = §ion->patches[patchID];
int32_t value = computeRPNExpr(patch, section);
/* `jr` is quite unlike the others... */
if (patch->type == PATCHTYPE_JR) {
/* Target is relative to the byte *after* the operand */
uint16_t address = section->org + patch->offset + 1;
int16_t offset = value - address;
if (offset < -128 || offset > 127)
errx(1, "%s(%d): jr target out of reach (expected -129 < %d < 128)",
patch->fileName, patch->lineNo, offset);
section->data[patch->offset] = offset & 0xFF;
} else {
/* Patch a certain number of bytes */
struct {
uint8_t size;
int32_t min;
int32_t max;
} const types[] = {
[PATCHTYPE_BYTE] = {1, -128, 255},
[PATCHTYPE_WORD] = {2, -32768, 65536},
[PATCHTYPE_LONG] = {4, INT32_MIN, INT32_MAX}
};
if (value < types[patch->type].min
|| value > types[patch->type].max)
errx(1, "%s(%d): Value %#x%s is not %u-bit",
patch->fileName, patch->lineNo, value,
value < 0 ? " (maybe negative?)" : "",
types[patch->type].size * 8);
for (uint8_t i = 0; i < types[patch->type].size; i++) {
section->data[patch->offset + i] = value & 0xFF;
value >>= 8;
}
}
}
}
void patch_ApplyPatches(void)
{
initRPNStack();
sect_ForEach(applyPatches, NULL);
freeRPNStack();
}