src/lib/rmodule.c

/* SPDX-License-Identifier: GPL-2.0-only */
/* This file is part of the coreboot project. */
#include <assert.h>
#include <cbmem.h>
#include <cbfs.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <console/console.h>
#include <program_loading.h>
#include <rmodule.h>

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

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;
}

int rmodule_calc_region(unsigned int region_alignment, size_t rmodule_size,
			size_t *region_size, int *load_offset)
{
	/* region_alignment must be a power of 2. */
	if (region_alignment & (region_alignment - 1))
		BUG();

	if (region_alignment < 4096)
		region_alignment = 4096;

	/* Sanity check rmodule_header size. The code below assumes it is less
	 * than the minimum alignment required. */
	if (region_alignment < sizeof(struct rmodule_header))
		BUG();

	/* 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. */
	*region_size = ALIGN(rmodule_size + 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
	 */
	*load_offset = region_alignment;

	return region_alignment - sizeof(struct rmodule_header);
}

int rmodule_stage_load(struct rmod_stage_load *rsl)
{
	struct rmodule rmod_stage;
	size_t region_size;
	char *stage_region;
	int rmodule_offset;
	int load_offset;
	struct cbfs_stage stage;
	void *rmod_loc;
	struct region_device *fh;

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

	fh = prog_rdev(rsl->prog);

	if (rdev_readat(fh, &stage, 0, sizeof(stage)) != sizeof(stage))
		return -1;

	rmodule_offset =
		rmodule_calc_region(DYN_CBMEM_ALIGN_SIZE,
				    stage.memlen, &region_size, &load_offset);

	stage_region = cbmem_add(rsl->cbmem_id, region_size);

	if (stage_region == NULL)
		return -1;

	rmod_loc = &stage_region[rmodule_offset];

	printk(BIOS_INFO, "Decompressing stage %s @ %p (%d bytes)\n",
	       prog_name(rsl->prog), rmod_loc, stage.memlen);

	if (!cbfs_load_and_decompress(fh, sizeof(stage), stage.len, rmod_loc,
				      stage.memlen, stage.compression))
		return -1;

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

	if (rmodule_load(&stage_region[load_offset], &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;
}