path: root/src/boot/elfboot.c

#include <console/console.h>
#include <part/fallback_boot.h>
#include <boot/elf.h>
#include <boot/elf_boot.h>
#include <boot/linuxbios_tables.h>
#include <ip_checksum.h>
#include <stream/read_bytes.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

/* Maximum physical address we can use for the linuxBIOS bounce buffer.
 */
#ifndef MAX_ADDR
#define MAX_ADDR -1UL
#endif

extern unsigned char _ram_seg;
extern unsigned char _eram_seg;

struct segment {
	struct segment *next;
	struct segment *prev;
	struct segment *phdr_next;
	struct segment *phdr_prev;
	unsigned long s_addr;
	unsigned long s_memsz;
	unsigned long s_offset;
	unsigned long s_filesz;
};

struct verify_callback {
	struct verify_callback *next;
	int (*callback)(struct verify_callback *vcb, 
		Elf_ehdr *ehdr, Elf_phdr *phdr, struct segment *head);
	unsigned long desc_offset;
	unsigned long desc_addr;
};

struct ip_checksum_vcb {
	struct verify_callback data;
	unsigned short ip_checksum;
};

int verify_ip_checksum(
	struct verify_callback *vcb, 
	Elf_ehdr *ehdr, Elf_phdr *phdr, struct segment *head)
{
	struct ip_checksum_vcb *cb;
	struct segment *ptr;
	unsigned long bytes;
	unsigned long checksum;
	unsigned char buff[2], *n_desc;
	cb = (struct ip_checksum_vcb *)vcb;
	/* zero the checksum so it's value won't
	 * get in the way of verifying the checksum.
	 */
	n_desc = 0;
	if (vcb->desc_addr) {
		n_desc = (unsigned char *)(vcb->desc_addr);
		memcpy(buff, n_desc, 2);
		memset(n_desc, 0, 2);
	}
	bytes = 0;
	checksum = compute_ip_checksum(ehdr, sizeof(*ehdr));
	bytes += sizeof(*ehdr);
	checksum = add_ip_checksums(bytes, checksum, 
		compute_ip_checksum(phdr, ehdr->e_phnum*sizeof(*phdr)));
	bytes += ehdr->e_phnum*sizeof(*phdr);
	for(ptr = head->phdr_next; ptr != head; ptr = ptr->phdr_next) {
		checksum = add_ip_checksums(bytes, checksum,
			compute_ip_checksum((void *)ptr->s_addr, ptr->s_memsz));
		bytes += ptr->s_memsz;
	}
	if (n_desc != 0) {
		memcpy(n_desc, buff, 2);
	}
	if (checksum != cb->ip_checksum) {
		printk_err("Image checksum: %04x != computed checksum: %04x\n",
			cb->ip_checksum, checksum);
	}
	return checksum == cb->ip_checksum;
}

/* The problem:  
 * Static executables all want to share the same addresses
 * in memory because only a few addresses are reliably present on
 * a machine, and implementing general relocation is hard.
 *
 * The solution:
 * - Allocate a buffer twice the size of the linuxBIOS image.
 * - Anything that would overwrite linuxBIOS copy into the lower half of
 *   the buffer. 
 * - After loading an ELF image copy linuxBIOS to the upper half of the
 *   buffer.
 * - Then jump to the loaded image.
 * 
 * Benefits:
 * - Nearly arbitrary standalone executables can be loaded.
 * - LinuxBIOS is preserved, so it can be returned to.
 * - The implementation is still relatively simple,
 *   and much simpler then the general case implemented in kexec.
 * 
 */

static unsigned long get_bounce_buffer(struct lb_memory *mem)
{
	unsigned long lb_size;
	unsigned long mem_entries;
	unsigned long buffer;
	int i;
	lb_size = (unsigned long)(&_eram_seg - &_ram_seg);
	/* Double linuxBIOS size so I have somewhere to place a copy to return to */
	lb_size = lb_size + lb_size;
	mem_entries = (mem->size - sizeof(*mem))/sizeof(mem->map[0]);
	buffer = 0;
	for(i = 0; i < mem_entries; i++) {
		unsigned long mstart, mend;
		unsigned long msize;
		unsigned long tbuffer;
		if (mem->map[i].type != LB_MEM_RAM)
			continue;
		if (mem->map[i].start > MAX_ADDR)
			continue;
		if (mem->map[i].size < lb_size)
			continue;
		mstart = mem->map[i].start;
		msize = MAX_ADDR - mstart +1;
		if (msize > mem->map[i].size)
			msize = mem->map[i].size;
		mend = mstart + msize;
		tbuffer = mend - lb_size;
		if (tbuffer < buffer) 
			continue;
		buffer = tbuffer;
	}
	return buffer;
}


static struct verify_callback *process_elf_notes(
	unsigned char *header, 
	unsigned long offset, unsigned long length)
{
	struct verify_callback *cb_chain;
	unsigned char *note, *end;
	char *program, *version;

	cb_chain = 0;
	note = header + offset;
	end = note + length;
	program = version = 0;
	while(note < end) {
		Elf_Nhdr *hdr;
		unsigned char *n_name, *n_desc, *next;
		hdr = (Elf_Nhdr *)note;
		n_name = note + sizeof(*hdr);
		n_desc = n_name + ((hdr->n_namesz + 3) & ~3);
		next = n_desc + ((hdr->n_descsz + 3) & ~3);
		if (next > end) {
			break;
		}
		if ((hdr->n_namesz == sizeof(ELF_NOTE_BOOT)) && 
			(memcmp(n_name, ELF_NOTE_BOOT, sizeof(ELF_NOTE_BOOT)) == 0)) {
			switch(hdr->n_type) {
			case EIN_PROGRAM_NAME:
				if (n_desc[hdr->n_descsz -1] == 0) {
					program = n_desc;
				}
				break;
			case EIN_PROGRAM_VERSION:
				if (n_desc[hdr->n_descsz -1] == 0) {
					version = n_desc;
				}
				break;
			case EIN_PROGRAM_CHECKSUM:
			{
				struct ip_checksum_vcb *cb;
				cb = malloc(sizeof(*cb));
				cb->ip_checksum = *((uint16_t *)n_desc);
				cb->data.callback = verify_ip_checksum;
				cb->data.next = cb_chain;
				cb->data.desc_offset = n_desc - header;
				cb_chain = &cb->data;
				break;
			}
			}
		}
		printk_spew("n_type: %08x n_name(%d): %-*.*s n_desc(%d): %-*.*s\n", 
			hdr->n_type,
			hdr->n_namesz, hdr->n_namesz, hdr->n_namesz, n_name,
			hdr->n_descsz,hdr->n_descsz, hdr->n_descsz, n_desc);
		note = next;
	}
	if (program && version) {
		printk_info("Loading %s version: %s\n",
			program, version);
	}
	return cb_chain;
}

static int valid_area(struct lb_memory *mem, unsigned long buffer,
	unsigned long start, unsigned long len)
{
	/* Check through all of the memory segments and ensure
	 * the segment that was passed in is completely contained
	 * in RAM.
	 */
	int i;
	unsigned long end = start + len;
	unsigned long mem_entries = (mem->size - sizeof(*mem))/sizeof(mem->map[0]);

	/* See if I conflict with the bounce buffer */
	if (end >= buffer) {
		return 0;
	}

	/* Walk through the table of valid memory ranges and see if I
	 * have a match.
	 */
	for(i = 0; i < mem_entries; i++) {
		uint64_t mstart, mend;
		uint32_t mtype;
		mtype = mem->map[i].type;
		mstart = mem->map[i].start;
		mend = mstart + mem->map[i].size;
		if ((mtype == LB_MEM_RAM) && (start < mend) && (end > mstart)) {
			break;
		}
	}
	if (i == mem_entries) {
		printk_err("No matching ram area found for range:\n");
		printk_err("  [0x%016lx, 0x%016lx)\n", start, end);
		printk_err("Ram areas\n");
		for(i = 0; i < mem_entries; i++) {
			uint64_t mstart, mend;
			uint32_t mtype;
			mtype = mem->map[i].type;
			mstart = mem->map[i].start;
			mend = mstart + mem->map[i].size;
			printk_err("  [0x%016lx, 0x%016lx) %s\n",
				(unsigned long)mstart, 
				(unsigned long)mend, 
				(mtype == LB_MEM_RAM)?"RAM":"Reserved");
			
		}
		return 0;
	}
	return 1;
}

static void relocate_segment(unsigned long buffer, struct segment *seg)
{
	/* Modify all segments that want to load onto linuxBIOS
	 * to load onto the bounce buffer instead.
	 */
	unsigned long lb_start = (unsigned long)&_ram_seg;
	unsigned long lb_end = (unsigned long)&_eram_seg;
	unsigned long start, middle, end;

	printk_spew("lb: [0x%016lx, 0x%016lx)\n", 
		lb_start, lb_end);

	start = seg->s_addr;
	middle = start + seg->s_filesz;
	end = start + seg->s_memsz;
	/* I don't conflict with linuxBIOS so get out of here */
	if ((end <= lb_start) || (start >= lb_end))
		return;

	printk_spew("segment: [0x%016lx, 0x%016lx, 0x%016lx)\n", 
		start, middle, end);

	/* Slice off a piece at the beginning
	 * that doesn't conflict with linuxBIOS.
	 */
	if (start < lb_start) {
		struct segment *new;
		unsigned long len = lb_start - start;
		new = malloc(sizeof(*new));
		*new = *seg;
		new->s_memsz = len;
		seg->s_memsz -= len;
		seg->s_addr += len;
		seg->s_offset += len;
		if (seg->s_filesz > len) {
			new->s_filesz = len;
			seg->s_filesz -= len;
		} else {
			seg->s_filesz = 0;
		}

		/* Order by stream offset */
		new->next = seg;
		new->prev = seg->prev;
		seg->prev->next = new;
		seg->prev = new;
		/* Order by original program header order */
		new->phdr_next = seg;
		new->phdr_prev = seg->phdr_prev;
		seg->phdr_prev->phdr_next = new;
		seg->phdr_prev = new;

		/* compute the new value of start */
		start = seg->s_addr;
		
		printk_spew("   early: [0x%016lx, 0x%016lx, 0x%016lx)\n", 
			new->s_addr, 
			new->s_addr + new->s_filesz,
			new->s_addr + new->s_memsz);
	}
	
	/* Slice off a piece at the end 
	 * that doesn't conflict with linuxBIOS 
	 */
	if (end > lb_end) {
		unsigned long len = lb_end - start;
		struct segment *new;
		new = malloc(sizeof(*new));
		*new = *seg;
		seg->s_memsz = len;
		new->s_memsz -= len;
		new->s_addr += len;
		new->s_offset += len;
		if (seg->s_filesz > len) {
			seg->s_filesz = len;
			new->s_filesz -= len;
		} else {
			new->s_filesz = 0;
		}
		/* Order by stream offset */
		new->next = seg->next;
		new->prev = seg;
		seg->next->prev = new;
		seg->next = new;
		/* Order by original program header order */
		new->phdr_next = seg->phdr_next;
		new->phdr_prev = seg;
		seg->phdr_next->phdr_prev = new;
		seg->phdr_next = new;

		/* compute the new value of end */
		end = start + len;
		
		printk_spew("   late: [0x%016lx, 0x%016lx, 0x%016lx)\n", 
			new->s_addr, 
			new->s_addr + new->s_filesz,
			new->s_addr + new->s_memsz);
		
	}
	/* Now retarget this segment onto the bounce buffer */
	seg->s_addr = buffer + (seg->s_addr - lb_start);

	printk_spew(" bounce: [0x%016lx, 0x%016lx, 0x%016lx)\n", 
		seg->s_addr, 
		seg->s_addr + seg->s_filesz, 
		seg->s_addr + seg->s_memsz);
}


static int build_elf_segment_list(
	struct segment *head, 
	unsigned long bounce_buffer, struct lb_memory *mem,
	Elf_phdr *phdr, int headers)
{
	struct segment *ptr;
	int i;
	memset(head, 0, sizeof(*head));
	head->phdr_next = head->phdr_prev = head;
	head->next = head->prev = head;
	for(i = 0; i < headers; i++) {
		struct segment *new;
		/* Ignore data that I don't need to handle */
		if (phdr[i].p_type != PT_LOAD) {
			printk_debug("Dropping non PT_LOAD segment\n");
			continue;
		}
		if (phdr[i].p_memsz == 0) {
			printk_debug("Dropping empty segment\n");
			continue;
		}
		new = malloc(sizeof(*new));
		new->s_addr = phdr[i].p_paddr;
		new->s_memsz = phdr[i].p_memsz;
		new->s_offset = phdr[i].p_offset;
		new->s_filesz = phdr[i].p_filesz;
		printk_debug("New segment addr 0x%lx size 0x%lx offset 0x%lx filesize 0x%lx\n",
			new->s_addr, new->s_memsz, new->s_offset, new->s_filesz);
		/* Clean up the values */
		if (new->s_filesz > new->s_memsz)  {
			new->s_filesz = new->s_memsz;
		}
		printk_debug("(cleaned up) New segment addr 0x%lx size 0x%lx offset 0x%lx filesize 0x%lx\n",
			new->s_addr, new->s_memsz, new->s_offset, new->s_filesz);
		for(ptr = head->next; ptr != head; ptr = ptr->next) {
			if (new->s_offset < ptr->s_offset)
				break;
		}
		/* Order by stream offset */
		new->next = ptr;
		new->prev = ptr->prev;
		ptr->prev->next = new;
		ptr->prev = new;
		/* Order by original program header order */
		new->phdr_next = head;
		new->phdr_prev = head->phdr_prev;
		head->phdr_prev->phdr_next  = new;
		head->phdr_prev = new;

		/* Verify the memory addresses in the segment are valid */
		if (!valid_area(mem, bounce_buffer, new->s_addr, new->s_memsz)) 
			goto out;

		/* Modify the segment to load onto the bounce_buffer if necessary.
		 */
		relocate_segment(bounce_buffer, new);
	}
	return 1;
 out:
	return 0;
}

static int load_elf_segments(
	struct segment *head, unsigned char *header, unsigned long header_size)
{
	unsigned long offset;
	struct segment *ptr;
	
	offset = 0;
	for(ptr = head->next; ptr != head; ptr = ptr->next) {
		unsigned long start_offset;
		unsigned long skip_bytes, read_bytes;
		unsigned char *dest, *middle, *end;
		byte_offset_t result;
		printk_debug("Loading Segment: addr: 0x%016lx memsz: 0x%016lx filesz: 0x%016lx\n",
			ptr->s_addr, ptr->s_memsz, ptr->s_filesz);
		
		/* Compute the boundaries of the segment */
		dest = (unsigned char *)(ptr->s_addr);
		end = dest + ptr->s_memsz;
		middle = dest + ptr->s_filesz;
		start_offset = ptr->s_offset;
		
		printk_spew("[ 0x%016lx, %016lx, 0x%016lx) <- %016lx\n",
			(unsigned long)dest,
			(unsigned long)middle,
			(unsigned long)end,
			(unsigned long)start_offset);
		
		/* Skip intial buffer unused bytes */
		if (offset < header_size) {
			if (start_offset < header_size) {
				offset = start_offset;
			} else {
				offset = header_size;
			}
		}
		
		/* Skip the unused bytes */
		skip_bytes = start_offset - offset;
		if (skip_bytes && 
			((result = stream_skip(skip_bytes)) != skip_bytes)) {
			printk_err("ERROR: Skip of %ld bytes skiped %ld bytes\n",
				skip_bytes, result);
			goto out;
		}
		offset = start_offset;
		
		/* Copy data from the initial buffer */
		if (offset < header_size) {
			size_t len;
			if ((ptr->s_filesz + start_offset) > header_size) {
				len = header_size - start_offset;
			}
			else {
				len = ptr->s_filesz;
			}
			memcpy(dest, &header[start_offset], len);
			dest += len;
		}
		
		/* Read the segment into memory */
		read_bytes = middle - dest;
		if (read_bytes && 
			((result = stream_read(dest, read_bytes)) != read_bytes)) {
			printk_err("ERROR: Read of %ld bytes read %ld bytes...\n",
				read_bytes, result);
			goto out;
		}
		offset += ptr->s_filesz;
		
		/* Zero the extra bytes between middle & end */
		if (middle < end) {
			printk_debug("Clearing Segment: addr: 0x%016lx memsz: 0x%016lx\n",
				(unsigned long)middle, end - middle);
			
			/* Zero the extra bytes */
			memset(middle, 0, end - middle);
		}
	}
	return 1;
 out:
	return 0;
}

static int verify_loaded_image(
	struct verify_callback *vcb,
	Elf_ehdr *ehdr, Elf_phdr *phdr,
	struct segment *head
	)
{
	struct segment *ptr;
	int ok;
	ok = 1;
	for(; ok && vcb ; vcb = vcb->next) {
		/* Find where the note is loaded */
		/* The whole note must be loaded intact
		 * so an address of 0 for the descriptor is impossible
		 */
		vcb->desc_addr = 0; 
		for(ptr = head->next; ptr != head; ptr = ptr->next) {
			unsigned long desc_addr;
			desc_addr = ptr->s_addr + vcb->desc_offset - ptr->s_offset;
			if ((desc_addr >= ptr->s_addr) &&
				(desc_addr < (ptr->s_addr + ptr->s_filesz))) {
				vcb->desc_addr = desc_addr;
			}
		}
		ok = vcb->callback(vcb, ehdr, phdr, head);
	}
	return ok;
}

int elfload(struct lb_memory *mem,
	unsigned char *header, unsigned long header_size)
{
	Elf_ehdr *ehdr;
	Elf_phdr *phdr;
	void *entry;
	struct segment head;
	struct verify_callback *cb_chain;
	unsigned long bounce_buffer;

	/* Find a bounce buffer so I can load to linuxBIOS's current location */
	bounce_buffer = get_bounce_buffer(mem);
	if (!bounce_buffer) {
		printk_err("Could not find a bounce buffer...\n");
		goto out;
	}

	ehdr = (Elf_ehdr *)header;
	entry = (void *)(ehdr->e_entry);
	phdr = (Elf_phdr *)(&header[ehdr->e_phoff]);

	/* Digest elf note information... */
	cb_chain = 0;
	if ((phdr[0].p_type == PT_NOTE) && 
		((phdr[0].p_offset + phdr[0].p_filesz) < header_size)) {
		cb_chain = process_elf_notes(header,
			phdr[0].p_offset, phdr[0].p_filesz);
	}

	/* Preprocess the elf segments */
	if (!build_elf_segment_list(&head, 
		bounce_buffer, mem, phdr, ehdr->e_phnum))
		goto out;

	/* Load the segments */
	if (!load_elf_segments(&head, header, header_size))
		goto out;

	printk_spew("Loaded segments\n");
	/* Verify the loaded image */
	if (!verify_loaded_image(cb_chain, ehdr, phdr, &head)) 
		goto out;

	printk_spew("verified segments\n");
	/* Shutdown the stream device */
	stream_fini();
	
	printk_spew("closed down stream\n");
	/* Reset to booting from this image as late as possible */
	boot_successful();

	printk_debug("Jumping to boot code at 0x%x\n", entry);
	post_code(0xfe);

	/* Jump to kernel */
	jmp_to_elf_entry(entry, bounce_buffer);
	return 1;

 out:
	return 0;
}

int elfboot(struct lb_memory *mem)
{
	Elf_ehdr *ehdr;
	static unsigned char header[ELF_HEAD_SIZE];
	int header_offset;
	int i, result;

	result = 0;
	printk_info("\n");
	printk_info("Welcome to %s, the open sourced starter.\n", BOOTLOADER);
	printk_info("January 2002, Eric Biederman.\n");
	printk_info("Version %s\n", BOOTLOADER_VERSION);
	printk_info("\n");
	post_code(0xf8);

	if (stream_init() < 0) {
		printk_err("Could not initialize driver...\n");
		goto out;
	}

	/* Read in the initial ELF_HEAD_SIZE bytes */
	if (stream_read(header, ELF_HEAD_SIZE) != ELF_HEAD_SIZE) {
		printk_err("Read failed...\n");
		goto out;
	}
	/* Scan for an elf header */
	header_offset = -1;
	for(i = 0; i < ELF_HEAD_SIZE - (sizeof(Elf_ehdr) + sizeof(Elf_phdr)); i+=16) {
		ehdr = (Elf_ehdr *)(&header[i]);
		if (memcmp(ehdr->e_ident, ELFMAG, 4) != 0) {
			printk_spew("NO header at %d\n", i);
			continue;
		}
		printk_debug("Found ELF candiate at offset %d\n", i);
		/* Sanity check the elf header */
		if ((ehdr->e_type == ET_EXEC) &&
			elf_check_arch(ehdr) &&
			(ehdr->e_ident[EI_VERSION] == EV_CURRENT) &&
			(ehdr->e_version == EV_CURRENT) &&
			(ehdr->e_ehsize == sizeof(Elf_ehdr)) &&
			(ehdr->e_phentsize = sizeof(Elf_phdr)) &&
			(ehdr->e_phoff < (ELF_HEAD_SIZE - i)) &&
			((ehdr->e_phoff + (ehdr->e_phentsize * ehdr->e_phnum)) <= 
				(ELF_HEAD_SIZE - i))) {
			header_offset = i;
			break;
		}
		ehdr = 0;
	}
	printk_spew("header_offset is %d\n", header_offset);
	if (header_offset == -1) {
		goto out;
	}

	printk_spew("Try to load at offset 0x%x\n", header_offset);
	result = elfload(mem, 
		header + header_offset , ELF_HEAD_SIZE - header_offset);
 out:
	if (!result) {
		/* Shutdown the stream device */
		stream_fini();

		printk_err("Cannot Load ELF Image\n");

		post_code(0xff);
	}
	return 0;

}