huge.cpp   [plain text]

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#include <stdint.h>
#include <math.h>
#include <unistd.h>
#include <dlfcn.h>
#include <mach/machine.h>

#include <vector>

#include "ld.hpp"
#include "huge.h"

namespace ld {
namespace passes {
namespace huge {

class NullAtom
{
public:
	bool operator()(const ld::Atom* atom) const {
		return (atom == NULL);
	}
};

void doPass(const Options& opts, ld::Internal& state)
{
	const bool log = false;
	
	// only make make __huge section in final linked images
	if ( opts.outputKind() == Options::kObjectFile )
		return;

	// only make make __huge section for x86_64
	if ( opts.architecture() != CPU_TYPE_X86_64 )
		return;

	// only needed if some (non-linkedit) atoms have an addresss >2GB from base address 
	state.usingHugeSections = false;
	uint64_t address = 0;
	for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
		ld::Internal::FinalSection* sect = *sit;
		if ( sect->type() == ld::Section::typePageZero )
			continue;
		if ( sect->type() == ld::Section::typeStack )
			continue;
		for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin(); ait != sect->atoms.end(); ++ait) {
			const ld::Atom* atom = *ait;
			if ( (address > 0x7FFFFFFFLL) && !sect->isSectionHidden() ) {
				state.usingHugeSections = true;
				if (log) fprintf(stderr, "atom: %s is >2GB (0x%09llX), so enabling huge mode\n", atom->name(), address);
				break;
			}
			address += atom->size();
		}
		if ( state.usingHugeSections )
			break;
	}
	if ( !state.usingHugeSections )
		return;

	// move all zero fill atoms that >1MB in size to a new __huge section
	ld::Internal::FinalSection* hugeSection = state.getFinalSection(ld::Section("__DATA", "__huge", ld::Section::typeZeroFill));
	for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
		ld::Internal::FinalSection* sect = *sit;
		if ( sect == hugeSection )
			continue;
		if ( sect->type() == ld::Section::typeZeroFill ) {
			bool movedSome = false;
			for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin(); ait != sect->atoms.end(); ++ait) {
				const ld::Atom* atom = *ait;
				if ( atom->size() > 1024*1024 ) {
					hugeSection->atoms.push_back(atom);
					if (log) fprintf(stderr, "moved to __huge: %s, size=%llu\n", atom->name(), atom->size());
					*ait = NULL;  // change atom to NULL for later bulk removal
					movedSome = true;
				}
			}
			if ( movedSome ) 
				sect->atoms.erase(std::remove_if(sect->atoms.begin(), sect->atoms.end(), NullAtom()), sect->atoms.end());
		}
	}

	
}


} // namespace huge
} // namespace passes 
} // namespace ld