Add partial KLD support for ELF. The module loading is not written yet.

2 files changed, 1006 insertions, 0 deletions

diff --git a/sys/kern/link_elf.c b/sys/kern/link_elf.c
new file mode 100644
index 0000000..c6db5ca
--- /dev/null
+++ b/sys/kern/link_elf.c
@@ -0,0 +1,503 @@
+/*-
+ * Copyright (c) 1998 Doug Rabson
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	$Id$
+ */
+
+#include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/systm.h>
+#include <sys/malloc.h>
+#include <sys/proc.h>
+#include <sys/namei.h>
+#include <sys/fcntl.h>
+#include <sys/vnode.h>
+#include <sys/linker.h>
+#include <machine/elf.h>
+
+static int	link_elf_load_file(const char*, linker_file_t*);
+static int	link_elf_lookup_symbol(linker_file_t, const char*,
+				       linker_sym_t*);
+static void	link_elf_symbol_values(linker_file_t, linker_sym_t, linker_symval_t*);
+static int	link_elf_search_symbol(linker_file_t, caddr_t value,
+				       linker_sym_t* sym, long* diffp);
+
+static void	link_elf_unload(linker_file_t);
+
+/*
+ * The file representing the currently running kernel.  This contains
+ * the global symbol table.
+ */
+
+linker_file_t linker_kernel_file;
+
+static struct linker_class_ops link_elf_class_ops = {
+    link_elf_load_file,
+};
+
+static struct linker_file_ops link_elf_file_ops = {
+    link_elf_lookup_symbol,
+    link_elf_symbol_values,
+    link_elf_search_symbol,
+    link_elf_unload,
+};
+
+typedef struct elf_file {
+    caddr_t		address;	/* Load address */
+    Elf_Dyn*		dynamic;	/* Symbol table etc. */
+    Elf_Off		nbuckets;	/* DT_HASH info */
+    Elf_Off		nchains;
+    const Elf_Off*	buckets;
+    const Elf_Off*	chains;
+    caddr_t		hash;
+    caddr_t		strtab;		/* DT_STRTAB */
+    Elf_Sym*		symtab;		/* DT_SYMTAB */
+} *elf_file_t;
+
+static int		parse_dynamic(linker_file_t lf);
+static int		load_dependancies(linker_file_t lf);
+static int		relocate_file(linker_file_t lf);
+
+/*
+ * The kernel symbol table starts here.
+ */
+extern struct _dynamic _DYNAMIC;
+
+static void
+link_elf_init(void* arg)
+{
+    Elf_Dyn* dp = (Elf_Dyn*) &_DYNAMIC;
+
+#if ELF_TARG_CLASS == ELFCLASS32
+    linker_add_class("elf32", NULL, &link_elf_class_ops);
+#else
+    linker_add_class("elf64", NULL, &link_elf_class_ops);
+#endif
+
+    if (dp) {
+	elf_file_t ef;
+
+	ef = malloc(sizeof(struct elf_file), M_LINKER, M_NOWAIT);
+	if (ef == NULL)
+	    panic("link_elf_init: Can't create linker structures for kernel");
+
+	ef->address = 0;
+	ef->dynamic = dp;
+	linker_kernel_file =
+	    linker_make_file(kernelname, ef, &link_elf_file_ops);
+	if (linker_kernel_file == NULL)
+	    panic("link_elf_init: Can't create linker structures for kernel");
+	parse_dynamic(linker_kernel_file);
+	/*
+	 * XXX there must be a better way of getting these constants.
+	 */
+#ifdef __alpha__
+	linker_kernel_file->address = (caddr_t) 0xfffffc0000300000;
+#else
+	linker_kernel_file->address = (caddr_t) 0xf0100000;
+#endif
+	linker_kernel_file->size = -(long)linker_kernel_file->address;
+	linker_current_file = linker_kernel_file;
+    }
+}
+
+SYSINIT(link_elf, SI_SUB_KMEM, SI_ORDER_THIRD, link_elf_init, 0);
+
+static int
+parse_dynamic(linker_file_t lf)
+{
+    elf_file_t ef = lf->priv;
+    Elf_Dyn *dp;
+
+    for (dp = ef->dynamic; dp->d_tag != DT_NULL; dp++) {
+	switch (dp->d_tag) {
+	case DT_HASH:
+	{
+	    /* From src/libexec/rtld-elf/rtld.c */
+	    const Elf_Off *hashtab = (const Elf_Off *)
+		(ef->address + dp->d_un.d_ptr);
+	    ef->nbuckets = hashtab[0];
+	    ef->nchains = hashtab[1];
+	    ef->buckets = hashtab + 2;
+	    ef->chains = ef->buckets + ef->nbuckets;
+	    break;
+	}
+	case DT_STRTAB:
+	    ef->strtab = (caddr_t) dp->d_un.d_ptr;
+	    break;
+	case DT_SYMTAB:
+	    ef->symtab = (Elf_Sym*) dp->d_un.d_ptr;
+	    break;
+	case DT_SYMENT:
+	    if (dp->d_un.d_val != sizeof(Elf_Sym))
+		return ENOEXEC;
+	}
+    }
+    return 0;
+}
+
+static int
+link_elf_load_file(const char* filename, linker_file_t* result)
+{
+#if 0
+    struct nameidata nd;
+    struct proc* p = curproc;	/* XXX */
+    int error = 0;
+    int resid;
+    struct exec header;
+    elf_file_t ef;
+    linker_file_t lf;
+
+    NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, filename, p);
+    error = vn_open(&nd, FREAD, 0);
+    if (error)
+	return error;
+
+    /*
+     * Read the a.out header from the file.
+     */
+    error = vn_rdwr(UIO_READ, nd.ni_vp, (void*) &header, sizeof header, 0,
+		    UIO_SYSSPACE, IO_NODELOCKED, p->p_ucred, &resid, p);
+    if (error)
+	goto out;
+
+    if (N_BADMAG(header) || !(N_GETFLAG(header) & EX_DYNAMIC))
+	goto out;
+
+    /*
+     * We have an a.out file, so make some space to read it in.
+     */
+    ef = malloc(sizeof(struct elf_file), M_LINKER, M_WAITOK);
+    ef->address = malloc(header.a_text + header.a_data + header.a_bss,
+			 M_LINKER, M_WAITOK);
+    
+    /*
+     * Read the text and data sections and zero the bss.
+     */
+    error = vn_rdwr(UIO_READ, nd.ni_vp, (void*) ef->address,
+		    header.a_text + header.a_data, 0,
+		    UIO_SYSSPACE, IO_NODELOCKED, p->p_ucred, &resid, p);
+    if (error)
+	goto out;
+    bzero(ef->address + header.a_text + header.a_data, header.a_bss);
+
+    /*
+     * Assume _DYNAMIC is the first data item.
+     */
+    ef->dynamic = (struct _dynamic*) (ef->address + header.a_text);
+    if (ef->dynamic->d_version != LD_VERSION_BSD) {
+	free(ef->address, M_LINKER);
+	free(ef, M_LINKER);
+	goto out;
+    }
+    (long) ef->dynamic->d_un.d_sdt += ef->address;
+
+    lf = linker_make_file(filename, ef, &link_elf_file_ops);
+    if (lf == NULL) {
+	free(ef->address, M_LINKER);
+	free(ef, M_LINKER);
+	error = ENOMEM;
+	goto out;
+    }
+    lf->address = ef->address;
+    lf->size = header.a_text + header.a_data + header.a_bss;
+
+    if ((error = load_dependancies(lf)) != 0
+	|| (error = relocate_file(lf)) != 0) {
+	linker_file_unload(lf);
+	goto out;
+    }
+
+    *result = lf;
+
+out:
+    VOP_UNLOCK(nd.ni_vp, 0, p);
+    vn_close(nd.ni_vp, FREAD, p->p_ucred, p);
+
+    return error;
+#else
+    return ENOEXEC;
+#endif
+}
+
+static void
+link_elf_unload(linker_file_t file)
+{
+    elf_file_t ef = file->priv;
+
+    if (ef) {
+	if (ef->address)
+	    free(ef->address, M_LINKER);
+	free(ef, M_LINKER);
+    }
+}
+
+#define ELF_RELOC(ef, type, off) (type*) ((ef)->address + (off))
+
+static int
+load_dependancies(linker_file_t lf)
+{
+#if 0
+    elf_file_t ef = lf->priv;
+    linker_file_t lfdep;
+    long off;
+    struct sod* sodp;
+    char* name;
+    char* filename = 0;
+    int error = 0;
+
+    /*
+     * All files are dependant on /kernel.
+     */
+    linker_kernel_file->refs++;
+    linker_file_add_dependancy(lf, linker_kernel_file);
+
+    off = LD_NEED(ef->dynamic);
+
+    /*
+     * Load the dependancies.
+     */
+    while (off != 0) {
+	sodp = ELF_RELOC(ef, struct sod, off);
+	name = ELF_RELOC(ef, char, sodp->sod_name);
+
+	/*
+	 * Prepend pathname if dep is not an absolute filename.
+	 */
+	if (name[0] != '/') {
+	    char* p;
+	    filename = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
+	    p = lf->filename + strlen(lf->filename) - 1;
+	    while (p >= lf->filename && *p != '/')
+		p--;
+	    if (p >= lf->filename) {
+		strncpy(filename, lf->filename, p - lf->filename);
+		filename[p - lf->filename] = '\0';
+		strcat(filename, "/");
+		strcat(filename, name);
+		name = filename;
+	    }
+	}
+	error = linker_load_file(name, &lfdep);
+	if (error)
+	    goto out;
+	error = linker_file_add_dependancy(lf, lfdep);
+	if (error)
+	    goto out;
+	off = sodp->sod_next;
+    }
+
+out:
+    if (filename)
+	free(filename, M_TEMP);
+    return error;
+#else
+    return ENOEXEC;
+#endif
+}
+
+#if 0
+/*
+ * XXX i386 dependant.
+ */
+static long
+read_relocation(struct relocation_info* r, char* addr)
+{
+    int length = r->r_length;
+    if (length == 0)
+	return *(u_char*) addr;
+    else if (length == 1)
+	return *(u_short*) addr;
+    else if (length == 2)
+	return *(u_int*) addr;
+    else
+	printf("link_elf: unsupported relocation size %d\n", r->r_length);
+    return 0;
+}
+
+static void
+write_relocation(struct relocation_info* r, char* addr, long value)
+{
+    int length = r->r_length;
+    if (length == 0)
+	*(u_char*) addr = value;
+    else if (length == 1)
+	*(u_short*) addr = value;
+    else if (length == 2)
+	*(u_int*) addr = value;
+    else
+	printf("link_elf: unsupported relocation size %d\n", r->r_length);
+}
+
+static int
+relocate_file(linker_file_t lf)
+{
+    elf_file_t ef = lf->priv;
+    struct relocation_info* rel;
+    struct relocation_info* erel;
+    struct relocation_info* r;
+    struct nzlist* symbolbase;
+    char* stringbase;
+    struct nzlist* np;
+    char* sym;
+    long relocation;
+
+    rel = ELF_RELOC(ef, struct relocation_info, LD_REL(ef->dynamic));
+    erel = ELF_RELOC(ef, struct relocation_info,
+		      LD_REL(ef->dynamic) + LD_RELSZ(ef->dynamic));
+    symbolbase = ELF_RELOC(ef, struct nzlist, LD_SYMBOL(ef->dynamic));
+    stringbase = ELF_RELOC(ef, char, LD_STRINGS(ef->dynamic));
+
+    for (r = rel; r < erel; r++) {
+	char* addr;
+
+	if (r->r_address == 0)
+	    break;
+
+	addr = ELF_RELOC(ef, char, r->r_address);
+	if (r->r_extern) {
+	    np = &symbolbase[r->r_symbolnum];
+	    sym = &stringbase[np->nz_strx];
+
+	    if (sym[0] != '_') {
+		printf("link_elf: bad symbol name %s\n", sym);
+		relocation = 0;
+	    } else
+		relocation = (long)
+		    linker_file_lookup_symbol(lf, sym + 1,
+					      np->nz_type != (N_SETV+N_EXT));
+	    if (!relocation) {
+		printf("link_elf: symbol %s not found\n", sym);
+		return ENOENT;
+	    }
+	    
+	    relocation += read_relocation(r, addr);
+
+	    if (r->r_jmptable) {
+		printf("link_elf: can't cope with jump table relocations\n");
+		continue;
+	    }
+
+	    if (r->r_pcrel)
+		relocation -= (long) ef->address;
+
+	    if (r->r_copy) {
+		printf("link_elf: can't cope with copy relocations\n");
+		continue;
+	    }
+	    
+	    write_relocation(r, addr, relocation);
+	} else {
+	    write_relocation(r, addr,
+			     (long)(read_relocation(r, addr) + ef->address));
+	}
+	
+    }
+
+    return 0;
+}
+
+static long
+symbol_hash_value(elf_file_t ef, const char* name)
+{
+    long hashval;
+    const char* p;
+
+    hashval = '_';		/* fake a starting '_' for C symbols */
+    for (p = name; *p; p++)
+	hashval = (hashval << 1) + *p;
+
+    return (hashval & 0x7fffffff) % LD_BUCKETS(ef->dynamic);
+}
+
+#endif
+
+int
+link_elf_lookup_symbol(linker_file_t lf, const char* name, linker_sym_t* sym)
+{
+	elf_file_t ef = lf->priv;
+	int symcount = ef->nchains;
+	Elf_Sym* es;
+	int i;
+
+	/* XXX use hash table */
+	for (i = 0, es = ef->symtab; i < ef->nchains; i++, es++) {
+		if (es->st_name == 0)
+			continue;
+		if (!strcmp(ef->strtab + es->st_name, name)) {
+			*sym = (linker_sym_t) es;
+			return 0;
+		}
+	}
+
+	return ENOENT;
+}
+
+static void
+link_elf_symbol_values(linker_file_t lf, linker_sym_t sym, linker_symval_t* symval)
+{
+	elf_file_t ef = lf->priv;
+	Elf_Sym* es = (Elf_Sym*) sym;
+
+	symval->name = ef->strtab + es->st_name;
+	symval->value = (caddr_t) es->st_value;
+	symval->size = es->st_size;
+}
+
+static int
+link_elf_search_symbol(linker_file_t lf, caddr_t value,
+		       linker_sym_t* sym, long* diffp)
+{
+	elf_file_t ef = lf->priv;
+	u_long off = (u_long) value;
+	u_long diff = off;
+	int symcount = ef->nchains;
+	Elf_Sym* es;
+	Elf_Sym* best = 0;
+	int i;
+
+	for (i = 0, es = ef->symtab; i < ef->nchains; i++, es++) {
+		if (es->st_name == 0)
+			continue;
+		if (off >= es->st_value) {
+			if (off - es->st_value < diff) {
+				diff = off - es->st_value;
+				best = es;
+				if (diff == 0)
+					break;
+			} else if (off - es->st_value == diff) {
+				best = es;
+			}
+		}
+	}
+	if (best == 0)
+		*diffp = off;
+	else
+		*diffp = diff;
+	*sym = (linker_sym_t) best;
+
+	return 0;
+}
+
diff --git a/sys/kern/link_elf_obj.c b/sys/kern/link_elf_obj.c
new file mode 100644
index 0000000..c6db5ca
--- /dev/null
+++ b/sys/kern/link_elf_obj.c
@@ -0,0 +1,503 @@
+/*-
+ * Copyright (c) 1998 Doug Rabson
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	$Id$
+ */
+
+#include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/systm.h>
+#include <sys/malloc.h>
+#include <sys/proc.h>
+#include <sys/namei.h>
+#include <sys/fcntl.h>
+#include <sys/vnode.h>
+#include <sys/linker.h>
+#include <machine/elf.h>
+
+static int	link_elf_load_file(const char*, linker_file_t*);
+static int	link_elf_lookup_symbol(linker_file_t, const char*,
+				       linker_sym_t*);
+static void	link_elf_symbol_values(linker_file_t, linker_sym_t, linker_symval_t*);
+static int	link_elf_search_symbol(linker_file_t, caddr_t value,
+				       linker_sym_t* sym, long* diffp);
+
+static void	link_elf_unload(linker_file_t);
+
+/*
+ * The file representing the currently running kernel.  This contains
+ * the global symbol table.
+ */
+
+linker_file_t linker_kernel_file;
+
+static struct linker_class_ops link_elf_class_ops = {
+    link_elf_load_file,
+};
+
+static struct linker_file_ops link_elf_file_ops = {
+    link_elf_lookup_symbol,
+    link_elf_symbol_values,
+    link_elf_search_symbol,
+    link_elf_unload,
+};
+
+typedef struct elf_file {
+    caddr_t		address;	/* Load address */
+    Elf_Dyn*		dynamic;	/* Symbol table etc. */
+    Elf_Off		nbuckets;	/* DT_HASH info */
+    Elf_Off		nchains;
+    const Elf_Off*	buckets;
+    const Elf_Off*	chains;
+    caddr_t		hash;
+    caddr_t		strtab;		/* DT_STRTAB */
+    Elf_Sym*		symtab;		/* DT_SYMTAB */
+} *elf_file_t;
+
+static int		parse_dynamic(linker_file_t lf);
+static int		load_dependancies(linker_file_t lf);
+static int		relocate_file(linker_file_t lf);
+
+/*
+ * The kernel symbol table starts here.
+ */
+extern struct _dynamic _DYNAMIC;
+
+static void
+link_elf_init(void* arg)
+{
+    Elf_Dyn* dp = (Elf_Dyn*) &_DYNAMIC;
+
+#if ELF_TARG_CLASS == ELFCLASS32
+    linker_add_class("elf32", NULL, &link_elf_class_ops);
+#else
+    linker_add_class("elf64", NULL, &link_elf_class_ops);
+#endif
+
+    if (dp) {
+	elf_file_t ef;
+
+	ef = malloc(sizeof(struct elf_file), M_LINKER, M_NOWAIT);
+	if (ef == NULL)
+	    panic("link_elf_init: Can't create linker structures for kernel");
+
+	ef->address = 0;
+	ef->dynamic = dp;
+	linker_kernel_file =
+	    linker_make_file(kernelname, ef, &link_elf_file_ops);
+	if (linker_kernel_file == NULL)
+	    panic("link_elf_init: Can't create linker structures for kernel");
+	parse_dynamic(linker_kernel_file);
+	/*
+	 * XXX there must be a better way of getting these constants.
+	 */
+#ifdef __alpha__
+	linker_kernel_file->address = (caddr_t) 0xfffffc0000300000;
+#else
+	linker_kernel_file->address = (caddr_t) 0xf0100000;
+#endif
+	linker_kernel_file->size = -(long)linker_kernel_file->address;
+	linker_current_file = linker_kernel_file;
+    }
+}
+
+SYSINIT(link_elf, SI_SUB_KMEM, SI_ORDER_THIRD, link_elf_init, 0);
+
+static int
+parse_dynamic(linker_file_t lf)
+{
+    elf_file_t ef = lf->priv;
+    Elf_Dyn *dp;
+
+    for (dp = ef->dynamic; dp->d_tag != DT_NULL; dp++) {
+	switch (dp->d_tag) {
+	case DT_HASH:
+	{
+	    /* From src/libexec/rtld-elf/rtld.c */
+	    const Elf_Off *hashtab = (const Elf_Off *)
+		(ef->address + dp->d_un.d_ptr);
+	    ef->nbuckets = hashtab[0];
+	    ef->nchains = hashtab[1];
+	    ef->buckets = hashtab + 2;
+	    ef->chains = ef->buckets + ef->nbuckets;
+	    break;
+	}
+	case DT_STRTAB:
+	    ef->strtab = (caddr_t) dp->d_un.d_ptr;
+	    break;
+	case DT_SYMTAB:
+	    ef->symtab = (Elf_Sym*) dp->d_un.d_ptr;
+	    break;
+	case DT_SYMENT:
+	    if (dp->d_un.d_val != sizeof(Elf_Sym))
+		return ENOEXEC;
+	}
+    }
+    return 0;
+}
+
+static int
+link_elf_load_file(const char* filename, linker_file_t* result)
+{
+#if 0
+    struct nameidata nd;
+    struct proc* p = curproc;	/* XXX */
+    int error = 0;
+    int resid;
+    struct exec header;
+    elf_file_t ef;
+    linker_file_t lf;
+
+    NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, filename, p);
+    error = vn_open(&nd, FREAD, 0);
+    if (error)
+	return error;
+
+    /*
+     * Read the a.out header from the file.
+     */
+    error = vn_rdwr(UIO_READ, nd.ni_vp, (void*) &header, sizeof header, 0,
+		    UIO_SYSSPACE, IO_NODELOCKED, p->p_ucred, &resid, p);
+    if (error)
+	goto out;
+
+    if (N_BADMAG(header) || !(N_GETFLAG(header) & EX_DYNAMIC))
+	goto out;
+
+    /*
+     * We have an a.out file, so make some space to read it in.
+     */
+    ef = malloc(sizeof(struct elf_file), M_LINKER, M_WAITOK);
+    ef->address = malloc(header.a_text + header.a_data + header.a_bss,
+			 M_LINKER, M_WAITOK);
+    
+    /*
+     * Read the text and data sections and zero the bss.
+     */
+    error = vn_rdwr(UIO_READ, nd.ni_vp, (void*) ef->address,
+		    header.a_text + header.a_data, 0,
+		    UIO_SYSSPACE, IO_NODELOCKED, p->p_ucred, &resid, p);
+    if (error)
+	goto out;
+    bzero(ef->address + header.a_text + header.a_data, header.a_bss);
+
+    /*
+     * Assume _DYNAMIC is the first data item.
+     */
+    ef->dynamic = (struct _dynamic*) (ef->address + header.a_text);
+    if (ef->dynamic->d_version != LD_VERSION_BSD) {
+	free(ef->address, M_LINKER);
+	free(ef, M_LINKER);
+	goto out;
+    }
+    (long) ef->dynamic->d_un.d_sdt += ef->address;
+
+    lf = linker_make_file(filename, ef, &link_elf_file_ops);
+    if (lf == NULL) {
+	free(ef->address, M_LINKER);
+	free(ef, M_LINKER);
+	error = ENOMEM;
+	goto out;
+    }
+    lf->address = ef->address;
+    lf->size = header.a_text + header.a_data + header.a_bss;
+
+    if ((error = load_dependancies(lf)) != 0
+	|| (error = relocate_file(lf)) != 0) {
+	linker_file_unload(lf);
+	goto out;
+    }
+
+    *result = lf;
+
+out:
+    VOP_UNLOCK(nd.ni_vp, 0, p);
+    vn_close(nd.ni_vp, FREAD, p->p_ucred, p);
+
+    return error;
+#else
+    return ENOEXEC;
+#endif
+}
+
+static void
+link_elf_unload(linker_file_t file)
+{
+    elf_file_t ef = file->priv;
+
+    if (ef) {
+	if (ef->address)
+	    free(ef->address, M_LINKER);
+	free(ef, M_LINKER);
+    }
+}
+
+#define ELF_RELOC(ef, type, off) (type*) ((ef)->address + (off))
+
+static int
+load_dependancies(linker_file_t lf)
+{
+#if 0
+    elf_file_t ef = lf->priv;
+    linker_file_t lfdep;
+    long off;
+    struct sod* sodp;
+    char* name;
+    char* filename = 0;
+    int error = 0;
+
+    /*
+     * All files are dependant on /kernel.
+     */
+    linker_kernel_file->refs++;
+    linker_file_add_dependancy(lf, linker_kernel_file);
+
+    off = LD_NEED(ef->dynamic);
+
+    /*
+     * Load the dependancies.
+     */
+    while (off != 0) {
+	sodp = ELF_RELOC(ef, struct sod, off);
+	name = ELF_RELOC(ef, char, sodp->sod_name);
+
+	/*
+	 * Prepend pathname if dep is not an absolute filename.
+	 */
+	if (name[0] != '/') {
+	    char* p;
+	    filename = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
+	    p = lf->filename + strlen(lf->filename) - 1;
+	    while (p >= lf->filename && *p != '/')
+		p--;
+	    if (p >= lf->filename) {
+		strncpy(filename, lf->filename, p - lf->filename);
+		filename[p - lf->filename] = '\0';
+		strcat(filename, "/");
+		strcat(filename, name);
+		name = filename;
+	    }
+	}
+	error = linker_load_file(name, &lfdep);
+	if (error)
+	    goto out;
+	error = linker_file_add_dependancy(lf, lfdep);
+	if (error)
+	    goto out;
+	off = sodp->sod_next;
+    }
+
+out:
+    if (filename)
+	free(filename, M_TEMP);
+    return error;
+#else
+    return ENOEXEC;
+#endif
+}
+
+#if 0
+/*
+ * XXX i386 dependant.
+ */
+static long
+read_relocation(struct relocation_info* r, char* addr)
+{
+    int length = r->r_length;
+    if (length == 0)
+	return *(u_char*) addr;
+    else if (length == 1)
+	return *(u_short*) addr;
+    else if (length == 2)
+	return *(u_int*) addr;
+    else
+	printf("link_elf: unsupported relocation size %d\n", r->r_length);
+    return 0;
+}
+
+static void
+write_relocation(struct relocation_info* r, char* addr, long value)
+{
+    int length = r->r_length;
+    if (length == 0)
+	*(u_char*) addr = value;
+    else if (length == 1)
+	*(u_short*) addr = value;
+    else if (length == 2)
+	*(u_int*) addr = value;
+    else
+	printf("link_elf: unsupported relocation size %d\n", r->r_length);
+}
+
+static int
+relocate_file(linker_file_t lf)
+{
+    elf_file_t ef = lf->priv;
+    struct relocation_info* rel;
+    struct relocation_info* erel;
+    struct relocation_info* r;
+    struct nzlist* symbolbase;
+    char* stringbase;
+    struct nzlist* np;
+    char* sym;
+    long relocation;
+
+    rel = ELF_RELOC(ef, struct relocation_info, LD_REL(ef->dynamic));
+    erel = ELF_RELOC(ef, struct relocation_info,
+		      LD_REL(ef->dynamic) + LD_RELSZ(ef->dynamic));
+    symbolbase = ELF_RELOC(ef, struct nzlist, LD_SYMBOL(ef->dynamic));
+    stringbase = ELF_RELOC(ef, char, LD_STRINGS(ef->dynamic));
+
+    for (r = rel; r < erel; r++) {
+	char* addr;
+
+	if (r->r_address == 0)
+	    break;
+
+	addr = ELF_RELOC(ef, char, r->r_address);
+	if (r->r_extern) {
+	    np = &symbolbase[r->r_symbolnum];
+	    sym = &stringbase[np->nz_strx];
+
+	    if (sym[0] != '_') {
+		printf("link_elf: bad symbol name %s\n", sym);
+		relocation = 0;
+	    } else
+		relocation = (long)
+		    linker_file_lookup_symbol(lf, sym + 1,
+					      np->nz_type != (N_SETV+N_EXT));
+	    if (!relocation) {
+		printf("link_elf: symbol %s not found\n", sym);
+		return ENOENT;
+	    }
+	    
+	    relocation += read_relocation(r, addr);
+
+	    if (r->r_jmptable) {
+		printf("link_elf: can't cope with jump table relocations\n");
+		continue;
+	    }
+
+	    if (r->r_pcrel)
+		relocation -= (long) ef->address;
+
+	    if (r->r_copy) {
+		printf("link_elf: can't cope with copy relocations\n");
+		continue;
+	    }
+	    
+	    write_relocation(r, addr, relocation);
+	} else {
+	    write_relocation(r, addr,
+			     (long)(read_relocation(r, addr) + ef->address));
+	}
+	
+    }
+
+    return 0;
+}
+
+static long
+symbol_hash_value(elf_file_t ef, const char* name)
+{
+    long hashval;
+    const char* p;
+
+    hashval = '_';		/* fake a starting '_' for C symbols */
+    for (p = name; *p; p++)
+	hashval = (hashval << 1) + *p;
+
+    return (hashval & 0x7fffffff) % LD_BUCKETS(ef->dynamic);
+}
+
+#endif
+
+int
+link_elf_lookup_symbol(linker_file_t lf, const char* name, linker_sym_t* sym)
+{
+	elf_file_t ef = lf->priv;
+	int symcount = ef->nchains;
+	Elf_Sym* es;
+	int i;
+
+	/* XXX use hash table */
+	for (i = 0, es = ef->symtab; i < ef->nchains; i++, es++) {
+		if (es->st_name == 0)
+			continue;
+		if (!strcmp(ef->strtab + es->st_name, name)) {
+			*sym = (linker_sym_t) es;
+			return 0;
+		}
+	}
+
+	return ENOENT;
+}
+
+static void
+link_elf_symbol_values(linker_file_t lf, linker_sym_t sym, linker_symval_t* symval)
+{
+	elf_file_t ef = lf->priv;
+	Elf_Sym* es = (Elf_Sym*) sym;
+
+	symval->name = ef->strtab + es->st_name;
+	symval->value = (caddr_t) es->st_value;
+	symval->size = es->st_size;
+}
+
+static int
+link_elf_search_symbol(linker_file_t lf, caddr_t value,
+		       linker_sym_t* sym, long* diffp)
+{
+	elf_file_t ef = lf->priv;
+	u_long off = (u_long) value;
+	u_long diff = off;
+	int symcount = ef->nchains;
+	Elf_Sym* es;
+	Elf_Sym* best = 0;
+	int i;
+
+	for (i = 0, es = ef->symtab; i < ef->nchains; i++, es++) {
+		if (es->st_name == 0)
+			continue;
+		if (off >= es->st_value) {
+			if (off - es->st_value < diff) {
+				diff = off - es->st_value;
+				best = es;
+				if (diff == 0)
+					break;
+			} else if (off - es->st_value == diff) {
+				best = es;
+			}
+		}
+	}
+	if (best == 0)
+		*diffp = off;
+	else
+		*diffp = diff;
+	*sym = (linker_sym_t) best;
+
+	return 0;
+}
+