/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Google Inc.
 *
 * ipa_module.cpp - Image Processing Algorithm module
 */

#include "ipa_module.h"

#include <algorithm>
#include <array>
#include <dlfcn.h>
#include <elf.h>
#include <errno.h>
#include <fcntl.h>
#include <link.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <tuple>
#include <unistd.h>

#include "log.h"
#include "pipeline_handler.h"
#include "utils.h"

/**
 * \file ipa_module.h
 * \brief Image Processing Algorithm module
 */

/**
 * \file ipa_module_info.h
 * \brief Image Processing Algorithm module information
 */

namespace libcamera {

LOG_DEFINE_CATEGORY(IPAModule)

namespace {

template<typename T>
typename std::remove_extent_t<T> *elfPointer(void *map, off_t offset,
					     size_t fileSize, size_t objSize)
{
	size_t size = offset + objSize;
	if (size > fileSize || size < objSize)
		return nullptr;

	return reinterpret_cast<typename std::remove_extent_t<T> *>
		(static_cast<char *>(map) + offset);
}

template<typename T>
typename std::remove_extent_t<T> *elfPointer(void *map, off_t offset,
					     size_t fileSize)
{
	return elfPointer<T>(map, offset, fileSize, sizeof(T));
}

int elfVerifyIdent(void *map, size_t soSize)
{
	char *e_ident = elfPointer<char[EI_NIDENT]>(map, 0, soSize);
	if (!e_ident)
		return -ENOEXEC;

	if (e_ident[EI_MAG0] != ELFMAG0 ||
	    e_ident[EI_MAG1] != ELFMAG1 ||
	    e_ident[EI_MAG2] != ELFMAG2 ||
	    e_ident[EI_MAG3] != ELFMAG3 ||
	    e_ident[EI_VERSION] != EV_CURRENT)
		return -ENOEXEC;

	int bitClass = sizeof(unsigned long) == 4 ? ELFCLASS32 : ELFCLASS64;
	if (e_ident[EI_CLASS] != bitClass)
		return -ENOEXEC;

	int a = 1;
	unsigned char endianness = *reinterpret_cast<char *>(&a) == 1
				 ? ELFDATA2LSB : ELFDATA2MSB;
	if (e_ident[EI_DATA] != endianness)
		return -ENOEXEC;

	return 0;
}

/**
 * \brief Retrieve address and size of a symbol from an mmap'ed ELF file
 * \param[in] map Address of mmap'ed ELF file
 * \param[in] soSize Size of mmap'ed ELF file (in bytes)
 * \param[in] symbol Symbol name
 *
 * \return zero or error code, address or nullptr, size of symbol or zero,
 * respectively
 */
std::tuple<void *, size_t>
elfLoadSymbol(void *map, size_t soSize, const char *symbol)
{
	ElfW(Ehdr) *eHdr = elfPointer<ElfW(Ehdr)>(map, 0, soSize);
	if (!eHdr)
		return std::make_tuple(nullptr, 0);

	off_t offset = eHdr->e_shoff + eHdr->e_shentsize * eHdr->e_shstrndx;
	ElfW(Shdr) *sHdr = elfPointer<ElfW(Shdr)>(map, offset, soSize);
	if (!sHdr)
		return std::make_tuple(nullptr, 0);
	off_t shnameoff = sHdr->sh_offset;

	/* Locate .dynsym section header. */
	ElfW(Shdr) *dynsym = nullptr;
	for (unsigned int i = 0; i < eHdr->e_shnum; i++) {
		offset = eHdr->e_shoff + eHdr->e_shentsize * i;
		sHdr = elfPointer<ElfW(Shdr)>(map, offset, soSize);
		if (!sHdr)
			return std::make_tuple(nullptr, 0);

		offset = shnameoff + sHdr->sh_name;
		char *name = elfPointer<char[8]>(map, offset, soSize);
		if (!name)
			return std::make_tuple(nullptr, 0);

		if (sHdr->sh_type == SHT_DYNSYM && !strcmp(name, ".dynsym")) {
			dynsym = sHdr;
			break;
		}
	}

	if (dynsym == nullptr) {
		LOG(IPAModule, Error) << "ELF has no .dynsym section";
		return std::make_tuple(nullptr, 0);
	}

	offset = eHdr->e_shoff + eHdr->e_shentsize * dynsym->sh_link;
	sHdr = elfPointer<ElfW(Shdr)>(map, offset, soSize);
	if (!sHdr)
		return std::make_tuple(nullptr, 0);
	off_t dynsym_nameoff = sHdr->sh_offset;

	/* Locate symbol in the .dynsym section. */
	ElfW(Sym) *targetSymbol = nullptr;
	unsigned int dynsym_num = dynsym->sh_size / dynsym->sh_entsize;
	for (unsigned int i = 0; i < dynsym_num; i++) {
		offset = dynsym->sh_offset + dynsym->sh_entsize * i;
		ElfW(Sym) *sym = elfPointer<ElfW(Sym)>(map, offset, soSize);
		if (!sym)
			return std::make_tuple(nullptr, 0);

		offset = dynsym_nameoff + sym->st_name;
		char *name = elfPointer<char>(map, offset, soSize,
					      strlen(symbol) + 1);
		if (!name)
			return std::make_tuple(nullptr, 0);

		if (!strcmp(name, symbol) &&
		    sym->st_info & STB_GLOBAL) {
			targetSymbol = sym;
			break;
		}
	}

	if (targetSymbol == nullptr) {
		LOG(IPAModule, Error) << "Symbol " << symbol << " not found";
		return std::make_tuple(nullptr, 0);
	}

	/* Locate and return data of symbol. */
	if (targetSymbol->st_shndx >= eHdr->e_shnum)
		return std::make_tuple(nullptr, 0);
	offset = eHdr->e_shoff + targetSymbol->st_shndx * eHdr->e_shentsize;
	sHdr = elfPointer<ElfW(Shdr)>(map, offset, soSize);
	if (!sHdr)
		return std::make_tuple(nullptr, 0);
	offset = sHdr->sh_offset + (targetSymbol->st_value - sHdr->sh_addr);
	char *data = elfPointer<char>(map, offset, soSize, targetSymbol->st_size);
	if (!data)
		return std::make_tuple(nullptr, 0);

	return std::make_tuple(data, targetSymbol->st_size);
}

} /* namespace */

/**
 * \def IPA_MODULE_API_VERSION
 * \brief The IPA module API version
 *
 * This version number specifies the version for the layout of
 * struct IPAModuleInfo. The IPA module shall use this macro to
 * set its moduleAPIVersion field.
 *
 * \sa IPAModuleInfo::moduleAPIVersion
 */

/**
 * \struct IPAModuleInfo
 * \brief Information of an IPA module
 *
 * This structure contains the information of an IPA module. It is loaded,
 * read, and validated before anything else is loaded from the shared object.
 *
 * \var IPAModuleInfo::moduleAPIVersion
 * \brief The IPA module API version that the IPA module implements
 *
 * This version number specifies the version for the layout of
 * struct IPAModuleInfo. The IPA module shall report here the version that
 * it was built for, using the macro IPA_MODULE_API_VERSION.
 *
 * \var IPAModuleInfo::pipelineVersion
 * \brief The pipeline handler version that the IPA module is for
 *
 * \var IPAModuleInfo::pipelineName
 * \brief The name of the pipeline handler that the IPA module is for
 *
 * This name is used to match a pipeline handler with the module.
 *
 * \var IPAModuleInfo::name
 * \brief The name of the IPA module
 *
 * \var IPAModuleInfo::license
 * \brief License of the IPA module
 *
 * This license is used to determine whether to force isolation of the IPA in
 * a separate process. If the license is "Proprietary", then the IPA will
 * be isolated. If the license is open-source, then the IPA will be allowed to
 * run without isolation if the user enables it. The license should be an
 * SPDX license string. The following licenses are currently available to
 * allow the IPA to run unisolated:
 *
 * - GPL-2.0-only
 * - GPL-2.0-or-later
 * - GPL-3.0-only
 * - GPL-3.0-or-later
 * - LGPL-2.1-only
 * - LGPL-2.1-or-later
 * - LGPL-3.0-only
 * - LGPL-3.0-or-later
 *
 * Any other license will cause the IPA to be run isolated.
 *
 * \todo Allow user to choose to isolate open source IPAs
 */

/**
 * \var ipaModuleInfo
 * \brief Information of an IPA module
 *
 * An IPA module must export a struct IPAModuleInfo of this name.
 */

/**
 * \class IPAModule
 * \brief Wrapper around IPA module shared object
 */