harvey/sys/src/libmach/executable.c

/*
 * This file is part of the UCB release of Plan 9. It is subject to the license
 * terms in the LICENSE file found in the top-level directory of this
 * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
 * part of the UCB release of Plan 9, including this file, may be copied,
 * modified, propagated, or distributed except according to the terms contained
 * in the LICENSE file.
 */

#include	<u.h>
#include	<libc.h>
#include	<bio.h>
#include	<mach.h>
#include	"elf.h"

/*
 *	All a.out header types.  The dummy entry allows canonical
 *	processing of the union as a sequence of longs
 */

typedef struct {
	union{
		struct {
			/* this will die soon. For now, just include it here. */
			int32_t	magic;		/* magic number */
			int32_t	text;	 	/* size of text segment */
			int32_t	data;	 	/* size of initialized data */
			int32_t	bss;	  	/* size of uninitialized data */
			int32_t	syms;	 	/* size of symbol table */
			int32_t	entry;	 	/* entry point */
			int32_t	spsz;		/* size of pc/sp offset table */
			int32_t	pcsz;		/* size of pc/line number table */
		};
		E64hdr E64hdr;
	} e;
	int32_t dummy;			/* padding to ensure extra long */
} ExecHdr;

static	int	elfdotout(int, Fhdr*, ExecHdr*);
static	void	setsym(Fhdr*, int32_t, int32_t, int32_t, int64_t);
static	void	setdata(Fhdr*, uint64_t, int32_t, int64_t,
				  int32_t);
static	void	settext(Fhdr*, uint64_t, uint64_t, int32_t,
				  int64_t);
static	void	hswal(void*, int, uint32_t(*)(uint32_t));

/*
 *	definition of per-executable file type structures
 */

typedef struct Exectable{
	int32_t	magic;			/* big-endian magic number of file */
	char	*name;			/* executable identifier */
	char	*dlmname;		/* dynamically loadable module identifier */
	uint8_t	type;			/* Internal code */
	uint8_t	_magic;			/* _MAGIC() magic */
	Mach	*mach;			/* Per-machine data */
	int32_t	hsize;			/* header size */
	uint32_t	(*swal)(uint32_t);		/* beswal or leswal */
	int	(*hparse)(int, Fhdr*, ExecHdr*);
} ExecTable;

extern	Mach	mamd64;

ExecTable exectab[] =
{
	{ ELF_MAG,			/* any ELF */
		"elf executable",
		nil,
		FNONE,
		0,
/*		&mi386,
		sizeof(Ehdr), */
		&mamd64,
		sizeof(E64hdr),
		nil,
		elfdotout },
	{ 0 },
};

Mach	*mach = &mamd64;

static ExecTable*
couldbe4k(ExecTable *mp)
{
//	Dir *d;
	ExecTable *f;

/* undefined for use with kernel
	if((d=dirstat("/proc/1/regs")) == nil)
		return mp;
	if(d->length < 32*8){		/ * R3000 * /
		free(d);
		return mp;
	}
	free(d); */
	for (f = exectab; f->magic; f++)
		if(f->magic == M_MAGIC) {
			f->name = "mips plan 9 executable on mips2 kernel";
			return f;
		}
	return mp;
}

int
crackhdr(int fd, Fhdr *fp)
{
	ExecTable *mp;
	ExecHdr d;
	int nb, ret;
	uint32_t magic;

	fp->type = FNONE;
	nb = read(fd, (char *)&d.e, sizeof(d.e));
	if (nb <= 0)
		return 0;

	ret = 0;
	magic = beswal(d.e.magic);		/* big-endian */
	for (mp = exectab; mp->magic; mp++) {
		if (nb < mp->hsize)
			continue;

		/*
		 * The magic number has morphed into something
		 * with fields (the straw was DYN_MAGIC) so now
		 * a flag is needed in Fhdr to distinguish _MAGIC()
		 * magic numbers from foreign magic numbers.
		 *
		 * This code is creaking a bit and if it has to
		 * be modified/extended much more it's probably
		 * time to step back and redo it all.
		 */
		if(mp->_magic){
			if(mp->magic != (magic & ~DYN_MAGIC))
				continue;

			if(mp->magic == V_MAGIC)
				mp = couldbe4k(mp);

			if ((magic & DYN_MAGIC) && mp->dlmname != nil)
				fp->name = mp->dlmname;
			else
				fp->name = mp->name;
		}
		else{
			if(mp->magic != magic)
				continue;
			fp->name = mp->name;
		}
		fp->type = mp->type;
		fp->hdrsz = mp->hsize;		/* will be zero on bootables */
		fp->_magic = mp->_magic;
		fp->magic = magic;

		mach = mp->mach;
		if(mp->swal != nil)
			hswal(&d, sizeof(d.e)/sizeof(uint32_t), mp->swal);
		ret = mp->hparse(fd, fp, &d);
		seek(fd, mp->hsize, 0);		/* seek to end of header */
		break;
	}
	if(mp->magic == 0)
		werrstr("unknown header type");
	return ret;
}

/*
 * Convert header to canonical form
 */
static void
hswal(void *v, int n, uint32_t (*swap)(uint32_t))
{
	uint32_t *ulp;

	for(ulp = v; n--; ulp++)
		*ulp = (*swap)(*ulp);
}

/*
 * ELF64 binaries.
 */
static int
elf64dotout(int fd, Fhdr *fp, ExecHdr *hp)
{
	E64hdr *ep;
	P64hdr *ph;
	uint16_t (*swab)(uint16_t);
	uint32_t (*swal)(uint32_t);
	uint64_t (*swav)(uint64_t);
	int i, it, id, is, phsz;
	uint64_t uvl;

	ep = &hp->e.E64hdr;
	if(ep->ident[DATA] == ELFDATA2LSB) {
		swab = leswab;
		swal = leswal;
		swav = leswav;
	} else if(ep->ident[DATA] == ELFDATA2MSB) {
		swab = beswab;
		swal = beswal;
		swav = beswav;
	} else {
		werrstr("bad ELF64 encoding - not big or little endian");
		return 0;
	}

	ep->type = swab(ep->type);
	ep->machine = swab(ep->machine);
	ep->version = swal(ep->version);
	if(ep->type != EXEC || ep->version != CURRENT)
		return 0;
	ep->elfentry = swav(ep->elfentry);
	ep->phoff = swav(ep->phoff);
	ep->shoff = swav(ep->shoff);
	ep->flags = swal(ep->flags);
	ep->ehsize = swab(ep->ehsize);
	ep->phentsize = swab(ep->phentsize);
	ep->phnum = swab(ep->phnum);
	ep->shentsize = swab(ep->shentsize);
	ep->shnum = swab(ep->shnum);
	ep->shstrndx = swab(ep->shstrndx);

	fp->magic = ELF_MAG;
	fp->hdrsz = (ep->ehsize+ep->phnum*ep->phentsize+16)&~15;
	switch(ep->machine) {
	default:
		return 0;
	case AMD64:
		mach = &mamd64;
		fp->type = FAMD64;
		fp->name = "amd64 ELF64 executable";
		break;
	case POWER64:
		fp->type = FPOWER64;
		fp->name = "power64 ELF64 executable";
		break;
	}

	if(ep->phentsize != sizeof(P64hdr)) {
		werrstr("bad ELF64 header size");
		return 0;
	}
	phsz = sizeof(P64hdr)*ep->phnum;
	ph = malloc(phsz);
	if(!ph)
		return 0;
	seek(fd, ep->phoff, 0);
	if(read(fd, ph, phsz) < 0) {
		free(ph);
		return 0;
	}
	for(i = 0; i < ep->phnum; i++) {
		ph[i].type = swal(ph[i].type);
		ph[i].flags = swal(ph[i].flags);
		ph[i].offset = swav(ph[i].offset);
		ph[i].vaddr = swav(ph[i].vaddr);
		ph[i].paddr = swav(ph[i].paddr);
		ph[i].filesz = swav(ph[i].filesz);
		ph[i].memsz = swav(ph[i].memsz);
		ph[i].align = swav(ph[i].align);
	}

	/* find text, data and symbols and install them */
	it = id = is = -1;
	for(i = 0; i < ep->phnum; i++) {
		if(ph[i].type == LOAD
		&& (ph[i].flags & (R|X)) == (R|X) && it == -1)
			it = i;
		else if(ph[i].type == LOAD
		&& (ph[i].flags & (R|W)) == (R|W) && id == -1)
			id = i;
		else if(ph[i].type == NOPTYPE && is == -1)
			is = i;
	}
	if(it == -1 || id == -1) {
		werrstr("No ELF64 TEXT or DATA sections");
		free(ph);
		return 0;
	}

	settext(fp, ep->elfentry, ph[it].vaddr, ph[it].memsz, ph[it].offset);
	/* 8c: out of fixed registers */
	uvl = ph[id].memsz - ph[id].filesz;
	setdata(fp, ph[id].vaddr, ph[id].filesz, ph[id].offset, uvl);
	if(is != -1)
		setsym(fp, ph[is].filesz, 0, ph[is].memsz, ph[is].offset);
	free(ph);
	return 1;
}

/*
 * Elf binaries.
 */
static int
elfdotout(int fd, Fhdr *fp, ExecHdr *hp)
{
//	Ehdr *ep;
	E64hdr *ep;

	/* bitswap the header according to the DATA format */
	ep = &hp->e.E64hdr;
//	if(ep->ident[CLASS] == ELFCLASS32)
//		return elf32dotout(fd, fp, hp);
//	else if(ep->ident[CLASS] == ELFCLASS64)
	if(ep->ident[CLASS] == ELFCLASS64)
		return elf64dotout(fd, fp, hp);

//	werrstr("bad ELF class - not 32- nor 64-bit");
	werrstr("bad ELF class - not 64-bit");
	return 0;
}

static void
settext(Fhdr *fp, uint64_t e, uint64_t a, int32_t s, int64_t off)
{
	fp->txtaddr = a;
	fp->entry = e;
	fp->txtsz = s;
	fp->txtoff = off;
}

static void
setdata(Fhdr *fp, uint64_t a, int32_t s, int64_t off, int32_t bss)
{
	fp->dataddr = a;
	fp->datsz = s;
	fp->datoff = off;
	fp->bsssz = bss;
}

static void
setsym(Fhdr *fp, int32_t symsz, int32_t sppcsz, int32_t lnpcsz,
       int64_t symoff)
{
	fp->symsz = symsz;
	fp->symoff = symoff;
	fp->sppcsz = sppcsz;
	fp->sppcoff = fp->symoff+fp->symsz;
	fp->lnpcsz = lnpcsz;
	fp->lnpcoff = fp->sppcoff+fp->sppcsz;
}