ref: dec4133e84e61fedc29c95cc3984f734422dff16
dir: /src/link/patch.c/
/*
* This file is part of RGBDS.
*
* Copyright (c) 2019, Eldred Habert and RGBDS contributors.
*
* SPDX-License-Identifier: MIT
*/
#include <assert.h>
#include <inttypes.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include "link/object.h"
#include "link/patch.h"
#include "link/section.h"
#include "link/symbol.h"
#include "error.h"
#include "linkdefs.h"
#include "opmath.h"
/*
* This is an "empty"-type stack. Apart from the actual values, we also remember
* whether the value is a placeholder inserted for error recovery. This allows
* us to avoid cascading errors.
*
* The best way to think about this is a stack of (value, errorFlag) pairs.
* They are only separated for reasons of memory efficiency.
*/
struct RPNStack {
int32_t *values;
bool *errorFlags;
size_t size;
size_t capacity;
} stack;
static void initRPNStack(void)
{
stack.capacity = 64;
stack.values = malloc(sizeof(*stack.values) * stack.capacity);
stack.errorFlags = malloc(sizeof(*stack.errorFlags) * stack.capacity);
if (!stack.values || !stack.errorFlags)
err("Failed to init RPN stack");
}
static void clearRPNStack(void)
{
stack.size = 0;
}
static void pushRPN(int32_t value, bool comesFromError)
{
if (stack.size >= stack.capacity) {
static const size_t increase_factor = 2;
if (stack.capacity > SIZE_MAX / increase_factor)
errx("Overflow in RPN stack resize");
stack.capacity *= increase_factor;
stack.values =
realloc(stack.values, sizeof(*stack.values) * stack.capacity);
stack.errorFlags =
realloc(stack.errorFlags, sizeof(*stack.errorFlags) * stack.capacity);
// Static analysis tools complain that the capacity might become
// zero due to overflow, but fail to realize that it's caught by
// the overflow check above. Hence the stringent check below.
if (!stack.values || !stack.errorFlags || !stack.capacity)
err("Failed to resize RPN stack");
}
stack.values[stack.size] = value;
stack.errorFlags[stack.size] = comesFromError;
stack.size++;
}
// This flag tracks whether the RPN op that is currently being evaluated
// has popped any values with the error flag set.
static bool isError = false;
static int32_t popRPN(struct FileStackNode const *node, uint32_t lineNo)
{
if (stack.size == 0)
fatal(node, lineNo, "Internal error, RPN stack empty");
stack.size--;
isError |= stack.errorFlags[stack.size];
return stack.values[stack.size];
}
static void freeRPNStack(void)
{
free(stack.values);
free(stack.errorFlags);
}
// RPN operators
static uint32_t getRPNByte(uint8_t const **expression, int32_t *size,
struct FileStackNode const *node, uint32_t lineNo)
{
if (!(*size)--)
fatal(node, lineNo, "Internal error, RPN expression overread");
return *(*expression)++;
}
static struct Symbol const *getSymbol(struct Symbol const * const *symbolList,
uint32_t index)
{
assert(index != (uint32_t)-1); // PC needs to be handled specially, not here
struct Symbol const *symbol = symbolList[index];
// If the symbol is defined elsewhere...
if (symbol->type == SYMTYPE_IMPORT)
return sym_GetSymbol(symbol->name);
return symbol;
}
/*
* 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
* @return isError Set if an error occurred during evaluation, and further
* errors caused by the value should be suppressed.
*/
static int32_t computeRPNExpr(struct Patch const *patch,
struct Symbol const * const *fileSymbols)
{
// Small shortcut to avoid a lot of repetition
#define popRPN() popRPN(patch->src, patch->lineNo)
uint8_t const *expression = patch->rpnExpression;
int32_t size = patch->rpnSize;
clearRPNStack();
while (size > 0) {
enum RPNCommand command = getRPNByte(&expression, &size,
patch->src, patch->lineNo);
int32_t value;
isError = false;
// 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();
if (value == 0) {
if (!isError)
error(patch->src, patch->lineNo, "Division by 0");
isError = true;
popRPN();
value = INT32_MAX;
} else {
value = op_divide(popRPN(), value);
}
break;
case RPN_MOD:
value = popRPN();
if (value == 0) {
if (!isError)
error(patch->src, patch->lineNo, "Modulo by 0");
isError = true;
popRPN();
value = 0;
} else {
value = op_modulo(popRPN(), value);
}
break;
case RPN_UNSUB:
value = -popRPN();
break;
case RPN_EXP:
value = popRPN();
if (value < 0) {
if (!isError)
error(patch->src, patch->lineNo, "Exponent by negative");
isError = true;
popRPN();
value = 0;
} else {
value = op_exponent(popRPN(), value);
}
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 = op_shift_left(popRPN(), value);
break;
case RPN_SHR:
value = popRPN();
value = op_shift_right(popRPN(), value);
break;
case RPN_USHR:
value = popRPN();
value = op_shift_right_unsigned(popRPN(), value);
break;
case RPN_BANK_SYM:
value = 0;
for (uint8_t shift = 0; shift < 32; shift += 8)
value |= getRPNByte(&expression, &size,
patch->src, patch->lineNo) << shift;
symbol = getSymbol(fileSymbols, value);
if (!symbol) {
error(patch->src, patch->lineNo,
"Requested BANK() of symbol \"%s\", which was not found",
fileSymbols[value]->name);
isError = true;
value = 1;
} else if (!symbol->section) {
error(patch->src, patch->lineNo,
"Requested BANK() of non-label symbol \"%s\"",
fileSymbols[value]->name);
isError = true;
value = 1;
} else {
value = symbol->section->bank;
}
break;
case RPN_BANK_SECT:
// `expression` is not guaranteed to be '\0'-terminated. If it is not,
// `getRPNByte` will have a fatal internal error.
// In either case, `getRPNByte` will not free `expression`.
name = (char const *)expression;
while (getRPNByte(&expression, &size, patch->src, patch->lineNo))
;
sect = sect_GetSection(name);
if (!sect) {
error(patch->src, patch->lineNo,
"Requested BANK() of section \"%s\", which was not found",
name);
isError = true;
value = 1;
} else {
value = sect->bank;
}
break;
case RPN_BANK_SELF:
if (!patch->pcSection) {
error(patch->src, patch->lineNo,
"PC has no bank outside a section");
isError = true;
value = 1;
} else {
value = patch->pcSection->bank;
}
break;
case RPN_SIZEOF_SECT:
// This has assumptions commented in the `RPN_BANK_SECT` case above.
name = (char const *)expression;
while (getRPNByte(&expression, &size, patch->src, patch->lineNo))
;
sect = sect_GetSection(name);
if (!sect) {
error(patch->src, patch->lineNo,
"Requested SIZEOF() of section \"%s\", which was not found",
name);
isError = true;
value = 1;
} else {
value = sect->size;
}
break;
case RPN_STARTOF_SECT:
// This has assumptions commented in the `RPN_BANK_SECT` case above.
name = (char const *)expression;
while (getRPNByte(&expression, &size, patch->src, patch->lineNo))
;
sect = sect_GetSection(name);
assert(sect->offset == 0);
if (!sect) {
error(patch->src, patch->lineNo,
"Requested STARTOF() of section \"%s\", which was not found",
name);
isError = true;
value = 1;
} else {
value = sect->org;
}
break;
case RPN_HRAM:
value = popRPN();
if (!isError && (value < 0
|| (value > 0xFF && value < 0xFF00)
|| value > 0xFFFF)) {
error(patch->src, patch->lineNo,
"Value %" PRId32 " is not in HRAM range", value);
isError = true;
}
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) {
if (!isError)
error(patch->src, patch->lineNo,
"Value %" PRId32 " is not a RST vector", value);
isError = true;
}
value |= 0xC7;
break;
case RPN_CONST:
value = 0;
for (uint8_t shift = 0; shift < 32; shift += 8)
value |= getRPNByte(&expression, &size,
patch->src, patch->lineNo) << shift;
break;
case RPN_SYM:
value = 0;
for (uint8_t shift = 0; shift < 32; shift += 8)
value |= getRPNByte(&expression, &size,
patch->src, patch->lineNo) << shift;
if (value == -1) { // PC
if (!patch->pcSection) {
error(patch->src, patch->lineNo,
"PC has no value outside a section");
value = 0;
isError = true;
} else {
value = patch->pcOffset + patch->pcSection->org;
}
} else {
symbol = getSymbol(fileSymbols, value);
if (!symbol) {
error(patch->src, patch->lineNo,
"Unknown symbol \"%s\"", fileSymbols[value]->name);
isError = true;
} else {
value = symbol->value;
// Symbols attached to sections have offsets
if (symbol->section)
value += symbol->section->org;
}
}
break;
}
pushRPN(value, isError);
}
if (stack.size > 1)
error(patch->src, patch->lineNo,
"RPN stack has %zu entries on exit, not 1", stack.size);
isError = false;
return popRPN();
#undef popRPN
}
void patch_CheckAssertions(struct Assertion *assert)
{
verbosePrint("Checking assertions...\n");
initRPNStack();
while (assert) {
int32_t value = computeRPNExpr(&assert->patch,
(struct Symbol const * const *)assert->fileSymbols);
enum AssertionType type = (enum AssertionType)assert->patch.type;
if (!isError && !value) {
switch (type) {
case ASSERT_FATAL:
fatal(assert->patch.src, assert->patch.lineNo, "%s",
assert->message[0] ? assert->message
: "assert failure");
// Not reached
break; // Here so checkpatch doesn't complain
case ASSERT_ERROR:
error(assert->patch.src, assert->patch.lineNo, "%s",
assert->message[0] ? assert->message
: "assert failure");
break;
case ASSERT_WARN:
warning(assert->patch.src, assert->patch.lineNo, "%s",
assert->message[0] ? assert->message
: "assert failure");
break;
}
} else if (isError && type == ASSERT_FATAL) {
fatal(assert->patch.src, assert->patch.lineNo,
"couldn't evaluate assertion%s%s",
assert->message[0] ? ": " : "",
assert->message);
}
struct Assertion *next = assert->next;
free(assert->patch.rpnExpression);
free(assert->message);
free(assert);
assert = next;
}
freeRPNStack();
}
/*
* Applies all of a section's patches
* @param section The section to patch
* @param arg Ignored callback arg
*/
static void applyFilePatches(struct Section *section, struct Section *dataSection)
{
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,
(struct Symbol const * const *)
section->fileSymbols);
uint16_t offset = patch->offset + section->offset;
// `jr` is quite unlike the others...
if (patch->type == PATCHTYPE_JR) {
// Offset is relative to the byte *after* the operand
// PC as operand to `jr` is lower than reference PC by 2
uint16_t address = patch->pcSection->org + patch->pcOffset + 2;
int16_t jumpOffset = value - address;
if (!isError && (jumpOffset < -128 || jumpOffset > 127))
error(patch->src, patch->lineNo,
"jr target out of reach (expected -129 < %" PRId16 " < 128)",
jumpOffset);
dataSection->data[offset] = jumpOffset & 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 (!isError && (value < types[patch->type].min
|| value > types[patch->type].max))
error(patch->src, patch->lineNo,
"Value %#" PRIx32 "%s is not %u-bit",
value, value < 0 ? " (maybe negative?)" : "",
types[patch->type].size * 8U);
for (uint8_t i = 0; i < types[patch->type].size; i++) {
dataSection->data[offset + i] = value & 0xFF;
value >>= 8;
}
}
}
}
/*
* Applies all of a section's patches, iterating over "components" of
* unionized sections
* @param section The section to patch
* @param arg Ignored callback arg
*/
static void applyPatches(struct Section *section, void *arg)
{
if (!sect_HasData(section->type))
return;
(void)arg;
struct Section *dataSection = section;
do {
applyFilePatches(section, dataSection);
section = section->nextu;
} while (section);
}
void patch_ApplyPatches(void)
{
initRPNStack();
sect_ForEach(applyPatches, NULL);
freeRPNStack();
}