src/lib/rmodule.c

/* SPDX-License-Identifier: GPL-2.0-only */

#include <assert.h>
#include <cbmem.h>
#include <cbfs.h>
#include <string.h>
#include <console/console.h>
#include <program_loading.h>
#include <rmodule.h>
#include <types.h>

/* Change this define to get more verbose debugging for module loading. */
#define PK_ADJ_LEVEL BIOS_NEVER

const size_t region_alignment = MIN_UNSAFE(DYN_CBMEM_ALIGN_SIZE, 4096);

static inline int rmodule_is_loaded(const struct rmodule *module)
{
	return module->location != NULL;
}

/* Calculate a loaded program address based on the blob address. */
static inline void *rmodule_load_addr(const struct rmodule *module,
				      uintptr_t blob_addr)
{
	char *loc = module->location;
	return &loc[blob_addr - module->header->module_link_start_address];
}

/* Initialize a rmodule structure based on raw data. */
int rmodule_parse(void *ptr, struct rmodule *module)
{
	char *base;
	struct rmodule_header *rhdr;

	base = ptr;
	rhdr = ptr;

	if (rhdr == NULL)
		return -1;

	/* Sanity check the raw data. */
	if (rhdr->magic != RMODULE_MAGIC)
		return -1;
	if (rhdr->version != RMODULE_VERSION_1)
		return -1;

	/* Indicate the module hasn't been loaded yet. */
	module->location = NULL;

	/* The rmodule only needs a reference to the reloc_header. */
	module->header = rhdr;

	/* The payload lives after the header. */
	module->payload = &base[rhdr->payload_begin_offset];
	module->payload_size = rhdr->payload_end_offset -
				rhdr->payload_begin_offset;
	module->relocations = &base[rhdr->relocations_begin_offset];

	return 0;
}

int rmodule_memory_size(const struct rmodule *module)
{
	return module->header->module_program_size;
}

void *rmodule_parameters(const struct rmodule *module)
{
	if (!rmodule_is_loaded(module))
		return NULL;

	/* Indicate if there are no parameters. */
	if (module->header->parameters_begin == module->header->parameters_end)
		return NULL;

	return rmodule_load_addr(module, module->header->parameters_begin);
}

int rmodule_entry_offset(const struct rmodule *module)
{
	return module->header->module_entry_point -
	       module->header->module_link_start_address;
}

void *rmodule_entry(const struct rmodule *module)
{
	if (!rmodule_is_loaded(module))
		return NULL;

	return rmodule_load_addr(module, module->header->module_entry_point);
}

static void rmodule_clear_bss(struct rmodule *module)
{
	char *begin;
	int size;

	begin = rmodule_load_addr(module, module->header->bss_begin);
	size = module->header->bss_end - module->header->bss_begin;
	memset(begin, 0, size);
}

static inline size_t rmodule_number_relocations(const struct rmodule *module)
{
	size_t r;

	r = module->header->relocations_end_offset;
	r -= module->header->relocations_begin_offset;
	r /= sizeof(uintptr_t);
	return r;
}

static void rmodule_copy_payload(const struct rmodule *module)
{
	printk(BIOS_DEBUG, "Loading module at %p with entry %p. "
	       "filesize: 0x%x memsize: 0x%x\n",
	       module->location, rmodule_entry(module),
	       module->payload_size, rmodule_memory_size(module));

	/* No need to copy the payload if the load location and the
	 * payload location are the same. */
	if (module->location == module->payload)
		return;

	memcpy(module->location, module->payload, module->payload_size);
}

static int rmodule_relocate(const struct rmodule *module)
{
	size_t num_relocations;
	const uintptr_t *reloc;
	uintptr_t adjustment;

	/* Each relocation needs to be adjusted relative to the beginning of
	 * the loaded program. */
	adjustment = (uintptr_t)rmodule_load_addr(module, 0);

	reloc = module->relocations;
	num_relocations = rmodule_number_relocations(module);

	printk(BIOS_DEBUG, "Processing %zu relocs. Offset value of 0x%08lx\n",
	       num_relocations, (unsigned long)adjustment);

	while (num_relocations > 0) {
		uintptr_t *adjust_loc;

		/* If the adjustment location is non-NULL adjust it. */
		adjust_loc = rmodule_load_addr(module, *reloc);
		printk(PK_ADJ_LEVEL, "Adjusting %p: 0x%08lx -> 0x%08lx\n",
		       adjust_loc, (unsigned long) *adjust_loc,
		       (unsigned long) (*adjust_loc + adjustment));
		*adjust_loc += adjustment;

		reloc++;
		num_relocations--;
	}

	return 0;
}

int rmodule_load_alignment(const struct rmodule *module)
{
	/* The load alignment is the start of the program's linked address.
	 * The base address where the program is loaded needs to be a multiple
	 * of the program's starting link address. That way all data alignment
	 * in the program is preserved. Default to 4KiB. */
	return 4096;
}

int rmodule_load(void *base, struct rmodule *module)
{
	/*
	 * In order to load the module at a given address, the following steps
	 * take place:
	 *  1. Copy payload to base address.
	 *  2. Adjust relocations within the module to new base address.
	 *  3. Clear the bss segment last since the relocations live where
	 *     the bss is. If an rmodule is being loaded from its load
	 *     address the relocations need to be processed before the bss.
	 */
	module->location = base;
	rmodule_copy_payload(module);
	if (rmodule_relocate(module))
		return -1;
	rmodule_clear_bss(module);

	prog_segment_loaded((uintptr_t)module->location,
				rmodule_memory_size(module), SEG_FINAL);

	return 0;
}

static void *rmodule_cbfs_allocator(void *rsl_arg, size_t unused,
				    const union cbfs_mdata *mdata)
{
	struct rmod_stage_load *rsl = rsl_arg;

	assert(IS_POWER_OF_2(region_alignment) &&
	       region_alignment >= sizeof(struct rmodule_header));

	/* The CBFS core just passes us the decompressed size of the file, but
	   we need to know the memlen of the binary image. We need to find and
	   parse the stage header explicitly. */
	const struct cbfs_file_attr_stageheader *sattr = cbfs_find_attr(mdata,
			CBFS_FILE_ATTR_TAG_STAGEHEADER, sizeof(*sattr));
	if (!sattr) {
		printk(BIOS_ERR, "rmodule '%s' has no stage header!\n",
		       rsl->prog->name);
		return NULL;
	}

	const size_t memlen = be32toh(sattr->memlen);

	/* Place the rmodule according to alignment. The rmodule files
	 * themselves are packed as a header and a payload, however the rmodule
	 * itself is linked along with the header. The header starts at address
	 * 0. Immediately following the header in the file is the program,
	 * however its starting address is determined by the rmodule linker
	 * script. In short, sizeof(struct rmodule_header) can be less than
	 * or equal to the linked address of the program. Therefore we want
	 * to place the rmodule so that the program falls on the aligned
	 * address with the header just before it. Therefore, we need at least
	 * a page to account for the size of the header. */
	size_t region_size = ALIGN_UP(memlen + region_alignment, 4096);
	/* The program starts immediately after the header. However,
	 * it needs to be aligned to a 4KiB boundary. Therefore, adjust the
	 * program location so that the program lands on a page boundary.  The
	 * layout looks like the following:
	 *
	 * +--------------------------------+  region_alignment + region_size
	 * |  >= 0 bytes from alignment     |
	 * +--------------------------------+  program end (4KiB aligned)
	 * |  program size                  |
	 * +--------------------------------+  program_begin (4KiB aligned)
	 * |  sizeof(struct rmodule_header) |
	 * +--------------------------------+  rmodule header start
	 * |  >= 0 bytes from alignment     |
	 * +--------------------------------+  region_alignment
	 */

	uint8_t *stage_region = cbmem_add(rsl->cbmem_id, region_size);
	if (stage_region == NULL)
		return NULL;

	return stage_region + region_alignment - sizeof(struct rmodule_header);
}

int rmodule_stage_load(struct rmod_stage_load *rsl)
{
	struct rmodule rmod_stage;

	if (rsl->prog == NULL || prog_name(rsl->prog) == NULL)
		return -1;

	if (prog_locate_hook(rsl->prog))
		return -1;

	void *rmod_loc = cbfs_alloc(prog_name(rsl->prog),
				    rmodule_cbfs_allocator, rsl, NULL);
	if (!rmod_loc)
		return -1;

	if (rmodule_parse(rmod_loc, &rmod_stage))
		return -1;

	if (rmodule_load(rmod_loc + sizeof(struct rmodule_header), &rmod_stage))
		return -1;

	prog_set_area(rsl->prog, rmod_stage.location,
			rmodule_memory_size(&rmod_stage));

	/* Allow caller to pick up parameters, if available. */
	rsl->params = rmodule_parameters(&rmod_stage);

	prog_set_entry(rsl->prog, rmodule_entry(&rmod_stage), rsl->params);

	return 0;
}