ref: 7903c14993dd6b5fdaaed6664fd6a8878b227ffd
dir: /src/link/assign.c/
/*
* This file is part of RGBDS.
*
* Copyright (c) 2019, Eldred Habert and RGBDS contributors.
*
* SPDX-License-Identifier: MIT
*/
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include "link/assign.h"
#include "link/section.h"
#include "link/symbol.h"
#include "link/object.h"
#include "link/main.h"
#include "link/script.h"
#include "link/output.h"
#include "extern/err.h"
#include "helpers.h"
struct MemoryLocation {
uint16_t address;
uint32_t bank;
};
struct FreeSpace {
uint16_t address;
uint16_t size;
struct FreeSpace *next, *prev;
};
/* Table of free space for each bank */
struct FreeSpace *memory[SECTTYPE_INVALID];
uint64_t nbSectionsToAssign;
/**
* Init the free space-modelling structs
*/
static void initFreeSpace(void)
{
for (enum SectionType type = 0; type < SECTTYPE_INVALID; type++) {
memory[type] = malloc(sizeof(*memory[type]) * nbbanks(type));
if (!memory[type])
err(1, "Failed to init free space for region %d", type);
for (uint32_t bank = 0; bank < nbbanks(type); bank++) {
memory[type][bank].next =
malloc(sizeof(*memory[type][0].next));
if (!memory[type][bank].next)
err(1, "Failed to init free space for region %d bank %u",
type, bank);
memory[type][bank].next->address = startaddr[type];
memory[type][bank].next->size = maxsize[type];
memory[type][bank].next->next = NULL;
memory[type][bank].next->prev = &memory[type][bank];
}
}
}
/**
* Alter sections' attributes based on the linker script
*/
static void processLinkerScript(void)
{
if (!linkerScriptName)
return;
verbosePrint("Reading linker script...\n");
linkerScript = openFile(linkerScriptName, "r");
/* Modify all sections according to the linker script */
struct SectionPlacement *placement;
while ((placement = script_NextSection())) {
struct Section *section = placement->section;
/* Check if this doesn't conflict with what the code says */
if (section->isBankFixed && placement->bank != section->bank)
errx(1, "Linker script contradicts \"%s\"'s bank placement",
section->name);
if (section->isAddressFixed && placement->org != section->org)
errx(1, "Linker script contradicts \"%s\"'s address placement",
section->name);
if (section->isAlignFixed
&& (placement->org & section->alignMask) != 0)
errx(1, "Linker script contradicts \"%s\"'s alignment",
section->name);
section->isAddressFixed = true;
section->org = placement->org;
section->isBankFixed = true;
section->bank = placement->bank;
section->isAlignFixed = false; /* The alignment is satisfied */
}
fclose(linkerScript);
}
/**
* Assigns a section to a given memory location
* @param section The section to assign
* @param location The location to assign the section to
*/
static inline void assignSection(struct Section *section,
struct MemoryLocation const *location)
{
section->org = location->address;
section->bank = location->bank;
nbSectionsToAssign--;
out_AddSection(section);
}
/**
* Checks whether a given location is suitable for placing a given section
* This checks not only that the location has enough room for the section, but
* also that the constraints (alignment...) are respected.
* @param section The section to be placed
* @param freeSpace The candidate free space to place the section into
* @param location The location to attempt placing the section at
* @return True if the location is suitable, false otherwise.
*/
static bool isLocationSuitable(struct Section const *section,
struct FreeSpace const *freeSpace,
struct MemoryLocation const *location)
{
if (section->isAddressFixed && section->org != location->address)
return false;
if (section->isAlignFixed && location->address & section->alignMask)
return false;
if (location->address < freeSpace->address)
return false;
return location->address + section->size
<= freeSpace->address + freeSpace->size;
}
/**
* Finds a suitable location to place a section at.
* @param section The section to be placed
* @param location A pointer to a location struct that will be filled
* @return A pointer to the free space encompassing the location, or NULL if
* none was found
*/
static struct FreeSpace *getPlacement(struct Section const *section,
struct MemoryLocation *location)
{
location->bank = section->isBankFixed
? section->bank
: bankranges[section->type][0];
struct FreeSpace *space;
for (;;) {
/* Switch to the beginning of the next bank */
#define BANK_INDEX (location->bank - bankranges[section->type][0])
space = memory[section->type][BANK_INDEX].next;
if (space)
location->address = space->address;
/* Process locations in that bank */
while (space) {
/* If that location is OK, return it */
if (isLocationSuitable(section, space, location))
return space;
/* Go to the next *possible* location */
if (section->isAddressFixed) {
/*
* If the address is fixed, there can be only
* one candidate block per bank; if we already
* reached it, give up.
*/
if (location->address < section->org)
location->address = section->org;
else
/* Try again in next bank */
space = NULL;
} else if (section->isAlignFixed) {
/* Move to next aligned location */
location->address &= ~section->alignMask;
location->address += section->alignMask + 1;
} else {
/* Any location is fine, so, next free block */
space = space->next;
if (space)
location->address = space->address;
}
/*
* If that location is past the current block's end,
* go forwards until that is no longer the case.
*/
while (space && location->address >=
space->address + space->size)
space = space->next;
/* Try again with the new location/free space combo */
}
if (section->isBankFixed)
return NULL;
/* Try again in the next bank */
location->bank++;
if (location->bank > bankranges[section->type][1])
return NULL;
#undef BANK_INDEX
}
}
/**
* Places a section in a suitable location, or error out if it fails to.
* @warning Due to the implemented algorithm, this should be called with
* sections of decreasing size.
* @param section The section to place
*/
static void placeSection(struct Section *section)
{
struct MemoryLocation location;
/* Specially handle 0-byte SECTIONs, as they can't overlap anything */
if (section->size == 0) {
/*
* Unless the SECTION's address was fixed, the starting address
* is fine for any alignment, as checked in sect_DoSanityChecks.
*/
location.address = section->isAddressFixed
? section->org
: startaddr[section->type];
location.bank = section->isBankFixed
? section->bank
: bankranges[section->type][0];
assignSection(section, &location);
return;
}
/*
* Place section using first-fit decreasing algorithm
* https://en.wikipedia.org/wiki/Bin_packing_problem#First-fit_algorithm
*/
struct FreeSpace *freeSpace = getPlacement(section, &location);
if (freeSpace) {
assignSection(section, &location);
/* Split the free space */
bool noLeftSpace = freeSpace->address == section->org;
bool noRightSpace = freeSpace->address + freeSpace->size
== section->org + section->size;
if (noLeftSpace && noRightSpace) {
/* The free space is entirely deleted */
freeSpace->prev->next = freeSpace->next;
if (freeSpace->next)
freeSpace->next->prev = freeSpace->prev;
/*
* If the space is the last one on the list, set its
* size to 0 so it doesn't get picked, but don't free()
* it as it will be freed when cleaning up
*/
free(freeSpace);
} else if (!noLeftSpace && !noRightSpace) {
/* The free space is split in two */
struct FreeSpace *newSpace = malloc(sizeof(*newSpace));
if (!newSpace)
err(1, "Failed to split new free space");
/* Append the new space after the chosen one */
newSpace->prev = freeSpace;
newSpace->next = freeSpace->next;
if (freeSpace->next)
freeSpace->next->prev = newSpace;
freeSpace->next = newSpace;
/* Set its parameters */
newSpace->address = section->org + section->size;
newSpace->size = freeSpace->address + freeSpace->size -
newSpace->address;
/* Set the original space's new parameters */
freeSpace->size = section->org - freeSpace->address;
/* address is unmodified */
} else {
/* The amount of free spaces doesn't change: resize! */
freeSpace->size -= section->size;
if (noLeftSpace)
/* The free space is moved *and* resized */
freeSpace->address += section->size;
}
return;
}
/* Please adjust depending on longest message below */
char where[64];
if (section->isBankFixed && nbbanks(section->type) != 1) {
if (section->isAddressFixed)
snprintf(where, 64, "at $%02x:%04x",
section->bank, section->org);
else if (section->isAlignFixed)
snprintf(where, 64, "in bank $%02x with align mask %x",
section->bank, ~section->alignMask);
else
snprintf(where, 64, "in bank $%02x", section->bank);
} else {
if (section->isAddressFixed)
snprintf(where, 64, "at address $%04x", section->org);
else if (section->isAlignFixed)
snprintf(where, 64, "with align mask %x",
~section->alignMask);
else
strcpy(where, "anywhere");
}
/* If a section failed to go to several places, nothing we can report */
if (!section->isBankFixed || !section->isAddressFixed)
errx(1, "Unable to place \"%s\" (%s section) %s",
section->name, typeNames[section->type], where);
/* If the section just can't fit the bank, report that */
else if (section->org + section->size > endaddr(section->type) + 1)
errx(1, "Unable to place \"%s\" (%s section) %s: section runs past end of region ($%04x > $%04x)",
section->name, typeNames[section->type], where,
section->org + section->size, endaddr(section->type) + 1);
/* Otherwise there is overlap with another section */
else
errx(1, "Unable to place \"%s\" (%s section) %s: section overlaps with \"%s\"",
section->name, typeNames[section->type], where,
out_OverlappingSection(section)->name);
}
struct UnassignedSection {
struct Section *section;
struct UnassignedSection *next;
};
#define BANK_CONSTRAINED (1 << 2)
#define ORG_CONSTRAINED (1 << 1)
#define ALIGN_CONSTRAINED (1 << 0)
static struct UnassignedSection *unassignedSections[1 << 3] = {0};
static struct UnassignedSection *sections;
/**
* Categorize a section depending on how constrained it is
* This is so the most-constrained sections are placed first
* @param section The section to categorize
* @param arg Callback arg, unused
*/
static void categorizeSection(struct Section *section, void *arg)
{
(void)arg;
uint8_t constraints = 0;
if (section->isBankFixed)
constraints |= BANK_CONSTRAINED;
if (section->isAddressFixed)
constraints |= ORG_CONSTRAINED;
/* Can't have both! */
else if (section->isAlignFixed)
constraints |= ALIGN_CONSTRAINED;
struct UnassignedSection **ptr = &unassignedSections[constraints];
/* Insert section while keeping the list sorted by decreasing size */
while (*ptr && (*ptr)->section->size > section->size)
ptr = &(*ptr)->next;
sections[nbSectionsToAssign].section = section;
sections[nbSectionsToAssign].next = *ptr;
*ptr = §ions[nbSectionsToAssign];
nbSectionsToAssign++;
}
void assign_AssignSections(void)
{
verbosePrint("Beginning assignment...\n");
/** Initialize assignment **/
/* Generate linked lists of sections to assign */
sections = malloc(sizeof(*sections) * nbSectionsToAssign + 1);
if (!sections)
err(1, "Failed to allocate memory for section assignment");
initFreeSpace();
/* Process linker script, if any */
processLinkerScript();
nbSectionsToAssign = 0;
sect_ForEach(categorizeSection, NULL);
/** Place sections, starting with the most constrained **/
/* Specially process fully-constrained sections because of overlaying */
struct UnassignedSection *sectionPtr =
unassignedSections[BANK_CONSTRAINED | ORG_CONSTRAINED];
verbosePrint("Assigning bank+org-constrained...\n");
while (sectionPtr) {
placeSection(sectionPtr->section);
sectionPtr = sectionPtr->next;
}
/* If all sections were fully constrained, we have nothing left to do */
if (!nbSectionsToAssign)
return;
/* Overlaying requires only fully-constrained sections */
verbosePrint("Assigning other sections...\n");
if (overlayFileName)
errx(1, "All sections must be fixed when using an overlay file; %u %sn't",
nbSectionsToAssign, nbSectionsToAssign == 1 ? "is" : "are");
/* Assign all remaining sections by decreasing constraint order */
for (int8_t constraints = BANK_CONSTRAINED | ALIGN_CONSTRAINED;
constraints >= 0; constraints--) {
sectionPtr = unassignedSections[constraints];
while (sectionPtr) {
placeSection(sectionPtr->section);
sectionPtr = sectionPtr->next;
}
if (!nbSectionsToAssign)
return;
}
trap_;
}
void assign_Cleanup(void)
{
for (enum SectionType type = 0; type < SECTTYPE_INVALID; type++) {
for (uint32_t bank = 0; bank < nbbanks(type); bank++) {
struct FreeSpace *ptr =
memory[type][bank].next;
while (ptr) {
struct FreeSpace *next = ptr->next;
free(ptr);
ptr = next;
}
}
free(memory[type]);
}
free(sections);
script_Cleanup();
}