kernel: Handle zero-length ELF sections better

[dragonfly.git] / sys / boot / common / load_elf_obj.c

/*-
 * Copyright (c) 2004 Ian Dowse <iedowse@freebsd.org>
 * Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
 * Copyright (c) 1998 Peter Wemm <peter@freebsd.org>
 * 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.
 *
 * $FreeBSD: src/sys/boot/common/load_elf_obj.c,v 1.2 2005/12/18 04:52:35 marcel Exp $
 */

#include <sys/param.h>
#include <sys/exec.h>
#include <sys/linker.h>
#include <sys/module.h>
#include <inttypes.h>
#include <string.h>
#include <machine/elf.h>
#include <stand.h>
#define FREEBSD_ELF
#include <link.h>

#include "bootstrap.h"

#define COPYOUT(s,d,l)  archsw.arch_copyout((vm_offset_t)(s), d, l)

#if defined(__i386__) && __ELF_WORD_SIZE == 64
#undef ELF_TARG_CLASS
#undef ELF_TARG_MACH
#define ELF_TARG_CLASS  ELFCLASS64
#define ELF_TARG_MACH   EM_X86_64
#endif

typedef struct elf_file {
        Elf_Ehdr        hdr;
        Elf_Shdr        *e_shdr;

        int             symtabindex;    /* Index of symbol table */
        int             shstrindex;     /* Index of section name string table */

        int             fd;
        vm_offset_t     off;
} *elf_file_t;

static int __elfN(obj_loadimage)(struct preloaded_file *mp, elf_file_t ef,
    u_int64_t loadaddr);
static int __elfN(obj_lookup_set)(struct preloaded_file *mp, elf_file_t ef,
    const char *name, Elf_Addr *startp, Elf_Addr *stopp, int *countp);
static int __elfN(obj_reloc_ptr)(struct preloaded_file *mp, elf_file_t ef,
    Elf_Addr p, void *val, size_t len);
static int __elfN(obj_parse_modmetadata)(struct preloaded_file *mp,
    elf_file_t ef);
static Elf_Addr __elfN(obj_symaddr)(struct elf_file *ef, Elf_Size symidx);

const char      *__elfN(obj_kerneltype) = "elf kernel";
const char      *__elfN(obj_moduletype) = "elf obj module";

/*
 * Attempt to load the file (file) as an ELF module.  It will be stored at
 * (dest), and a pointer to a module structure describing the loaded object
 * will be saved in (result).
 */
int
__elfN(obj_loadfile)(char *filename, u_int64_t dest,
    struct preloaded_file **result)
{
        struct preloaded_file *fp, *kfp;
        struct elf_file ef;
        Elf_Ehdr *hdr;
        int err;
        ssize_t bytes_read;

        fp = NULL;
        bzero(&ef, sizeof(struct elf_file));

        /*
         * Open the image, read and validate the ELF header
         */
        if (filename == NULL)   /* can't handle nameless */
                return(EFTYPE);
        if ((ef.fd = rel_open(filename, NULL, O_RDONLY)) == -1)
                return(errno);

        hdr = &ef.hdr;
        bytes_read = read(ef.fd, hdr, sizeof(*hdr));
        if (bytes_read != sizeof(*hdr)) {
                err = EFTYPE;   /* could be EIO, but may be small file */
                goto oerr;
        }

        /* Is it ELF? */
        if (!IS_ELF(*hdr)) {
                err = EFTYPE;
                goto oerr;
        }
        if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS || /* Layout ? */
            hdr->e_ident[EI_DATA] != ELF_TARG_DATA ||
            hdr->e_ident[EI_VERSION] != EV_CURRENT ||   /* Version ? */
            hdr->e_version != EV_CURRENT ||
            hdr->e_machine != ELF_TARG_MACH ||          /* Machine ? */
            hdr->e_type != ET_REL) {
                err = EFTYPE;
                goto oerr;
        }

        if (hdr->e_shnum * hdr->e_shentsize == 0 || hdr->e_shoff == 0 ||
            hdr->e_shentsize != sizeof(Elf_Shdr)) {
                err = EFTYPE;
                goto oerr;
        }

        kfp = file_findfile(NULL, NULL);
        if (kfp == NULL) {
                printf("elf" __XSTRING(__ELF_WORD_SIZE)
                    "_obj_loadfile: can't load module before kernel\n");
                err = EPERM;
                goto oerr;
        }
        if (strcmp(__elfN(obj_kerneltype), kfp->f_type)) {
                printf("elf" __XSTRING(__ELF_WORD_SIZE)
                    "_obj_loadfile: can't load module with kernel type '%s'\n",
                    kfp->f_type);
                err = EPERM;
                goto oerr;
        }

        /* Page-align the load address */
        dest = roundup(dest, PAGE_SIZE);

        /*
         * Ok, we think we should handle this.
         */
        fp = file_alloc();
        if (fp == NULL) {
                printf("elf" __XSTRING(__ELF_WORD_SIZE)
                    "_obj_loadfile: cannot allocate module info\n");
                err = EPERM;
                goto out;
        }
        fp->f_name = strdup(filename);
        fp->f_type = strdup(__elfN(obj_moduletype));

        printf("%s ", filename);

        fp->f_size = __elfN(obj_loadimage)(fp, &ef, dest);
        if (fp->f_size == 0 || fp->f_addr == 0)
                goto ioerr;

        /* save exec header as metadata */
        file_addmetadata(fp, MODINFOMD_ELFHDR, sizeof(*hdr), hdr);

        /* Load OK, return module pointer */
        *result = (struct preloaded_file *)fp;
        err = 0;
        goto out;

ioerr:
        err = EIO;
oerr:
        file_discard(fp);
out:
        close(ef.fd);
        if (ef.e_shdr != NULL)
                free(ef.e_shdr);

        return(err);
}

/*
 * With the file (fd) open on the image, and (ehdr) containing
 * the Elf header, load the image at (off)
 */
static int
__elfN(obj_loadimage)(struct preloaded_file *fp, elf_file_t ef, u_int64_t off)
{
        Elf_Ehdr *hdr;
        Elf_Shdr *shdr;
        vm_offset_t firstaddr, lastaddr;
        int i, nsym, res, ret, shdrbytes, symstrindex;

        ret = 0;
        firstaddr = lastaddr = (vm_offset_t)off;
        hdr = &ef->hdr;
        ef->off = (vm_offset_t)off;

        /* Read in the section headers. */
        shdrbytes = hdr->e_shnum * hdr->e_shentsize;
        shdr = alloc_pread(ef->fd, (off_t)hdr->e_shoff, shdrbytes);
        if (shdr == NULL) {
                printf("\nelf" __XSTRING(__ELF_WORD_SIZE)
                    "_obj_loadimage: read section headers failed\n");
                goto out;
        }
        ef->e_shdr = shdr;

        /*
         * Decide where to load everything, but don't read it yet.
         * We store the load address as a non-zero sh_addr value.
         * Start with the code/data and bss.
         */
        for (i = 0; i < hdr->e_shnum; i++)
                shdr[i].sh_addr = 0;
        for (i = 0; i < hdr->e_shnum; i++) {
                if (shdr[i].sh_size == 0)
                        continue;
                switch (shdr[i].sh_type) {
                case SHT_PROGBITS:
                case SHT_NOBITS:
                        lastaddr = roundup(lastaddr, shdr[i].sh_addralign);
                        shdr[i].sh_addr = (Elf_Addr)lastaddr;
                        lastaddr += shdr[i].sh_size;
                        break;
                }
        }

        /* Symbols. */
        nsym = 0;
        for (i = 0; i < hdr->e_shnum; i++) {
                switch (shdr[i].sh_type) {
                case SHT_SYMTAB:
                        nsym++;
                        ef->symtabindex = i;
                        shdr[i].sh_addr = (Elf_Addr)lastaddr;
                        lastaddr += shdr[i].sh_size;
                        break;
                }
        }
        if (nsym != 1) {
                printf("\nelf" __XSTRING(__ELF_WORD_SIZE)
                    "_obj_loadimage: file has no valid symbol table\n");
                goto out;
        }
        lastaddr = roundup(lastaddr, shdr[ef->symtabindex].sh_addralign);
        shdr[ef->symtabindex].sh_addr = (Elf_Addr)lastaddr;
        lastaddr += shdr[ef->symtabindex].sh_size;

        symstrindex = shdr[ef->symtabindex].sh_link;
        if (symstrindex < 0 || symstrindex >= hdr->e_shnum ||
            shdr[symstrindex].sh_type != SHT_STRTAB) {
                printf("\nelf" __XSTRING(__ELF_WORD_SIZE)
                    "_obj_loadimage: file has invalid symbol strings\n");
                goto out;
        }
        lastaddr = roundup(lastaddr, shdr[symstrindex].sh_addralign);
        shdr[symstrindex].sh_addr = (Elf_Addr)lastaddr;
        lastaddr += shdr[symstrindex].sh_size;

        /* Section names. */
        if (hdr->e_shstrndx == 0 || hdr->e_shstrndx >= hdr->e_shnum ||
            shdr[hdr->e_shstrndx].sh_type != SHT_STRTAB) {
                printf("\nelf" __XSTRING(__ELF_WORD_SIZE)
                    "_obj_loadimage: file has no section names\n");
                goto out;
        }
        ef->shstrindex = hdr->e_shstrndx;
        lastaddr = roundup(lastaddr, shdr[ef->shstrindex].sh_addralign);
        shdr[ef->shstrindex].sh_addr = (Elf_Addr)lastaddr;
        lastaddr += shdr[ef->shstrindex].sh_size;

        /* Relocation tables. */
        for (i = 0; i < hdr->e_shnum; i++) {
                switch (shdr[i].sh_type) {
                case SHT_REL:
                case SHT_RELA:
                        lastaddr = roundup(lastaddr, shdr[i].sh_addralign);
                        shdr[i].sh_addr = (Elf_Addr)lastaddr;
                        lastaddr += shdr[i].sh_size;
                        break;
                }
        }

        /* Clear the whole area, including bss regions. */
        kern_bzero(firstaddr, lastaddr - firstaddr);

        /* Now read it all in. */
        for (i = 0; i < hdr->e_shnum; i++) {
                if (shdr[i].sh_addr == 0 || shdr[i].sh_type == SHT_NOBITS)
                        continue;
                if (kern_pread(ef->fd, (vm_offset_t)shdr[i].sh_addr,
                    shdr[i].sh_size, (off_t)shdr[i].sh_offset) != 0) {
                        printf("\nelf" __XSTRING(__ELF_WORD_SIZE)
                            "_obj_loadimage: read failed\n");
                        goto out;
                }
        }

        file_addmetadata(fp, MODINFOMD_SHDR, shdrbytes, shdr);

        res = __elfN(obj_parse_modmetadata)(fp, ef);
        if (res != 0)
                goto out;

        ret = lastaddr - firstaddr;
        fp->f_addr = firstaddr;

        printf("size 0x%lx at 0x%lx", (u_long)ret, (u_long)firstaddr);

out:
        printf("\n");
        return ret;
}

#if defined(__i386__) && __ELF_WORD_SIZE == 64
struct mod_metadata64 {
        int             md_version;     /* structure version MDTV_* */
        int             md_type;        /* type of entry MDT_* */
        u_int64_t       md_data;        /* specific data */
        u_int64_t       md_cval;        /* common string label */
};
#endif

int
__elfN(obj_parse_modmetadata)(struct preloaded_file *fp, elf_file_t ef)
{
        struct mod_metadata md;
#if defined(__i386__) && __ELF_WORD_SIZE == 64
        struct mod_metadata64 md64;
#endif
        struct mod_depend *mdepend;
        struct mod_version mver;
        char *s;
        int error, modcnt, minfolen;
        Elf_Addr v, p, p_stop;

        if (__elfN(obj_lookup_set)(fp, ef, "modmetadata_set", &p, &p_stop,
            &modcnt) != 0)
                return ENOENT;

        modcnt = 0;
        while (p < p_stop) {
                COPYOUT(p, &v, sizeof(v));
                error = __elfN(obj_reloc_ptr)(fp, ef, p, &v, sizeof(v));
                if (error != 0)
                        return (error);
#if defined(__i386__) && __ELF_WORD_SIZE == 64
                COPYOUT(v, &md64, sizeof(md64));
                error = __elfN(obj_reloc_ptr)(fp, ef, v, &md64, sizeof(md64));
                if (error != 0)
                        return (error);
                md.md_version = md64.md_version;
                md.md_type = md64.md_type;
                md.md_cval = (const char *)(uintptr_t)md64.md_cval;
                md.md_data = (void *)(uintptr_t)md64.md_data;
#else
                COPYOUT(v, &md, sizeof(md));
                error = __elfN(obj_reloc_ptr)(fp, ef, v, &md, sizeof(md));
                if (error != 0)
                        return (error);
#endif
                p += sizeof(Elf_Addr);
                switch(md.md_type) {
                case MDT_DEPEND:
                        s = strdupout((vm_offset_t)md.md_cval);
                        minfolen = sizeof(*mdepend) + strlen(s) + 1;
                        mdepend = malloc(minfolen);
                        if (mdepend == NULL)
                                return ENOMEM;
                        COPYOUT((vm_offset_t)md.md_data, mdepend,
                            sizeof(*mdepend));
                        strcpy((char*)(mdepend + 1), s);
                        free(s);
                        file_addmetadata(fp, MODINFOMD_DEPLIST, minfolen,
                            mdepend);
                        free(mdepend);
                        break;
                case MDT_VERSION:
                        s = strdupout((vm_offset_t)md.md_cval);
                        COPYOUT((vm_offset_t)md.md_data, &mver, sizeof(mver));
                        file_addmodule(fp, s, mver.mv_version, NULL);
                        free(s);
                        modcnt++;
                        break;
                case MDT_MODULE:
                        break;
                default:
                        printf("unknown type %d\n", md.md_type);
                        break;
                }
        }
        return 0;
}

static int
__elfN(obj_lookup_set)(struct preloaded_file *fp, elf_file_t ef,
    const char* name, Elf_Addr *startp, Elf_Addr *stopp, int *countp)
{
        Elf_Ehdr *hdr;
        Elf_Shdr *shdr;
        char *p;
        vm_offset_t shstrtab;
        int i;

        hdr = &ef->hdr;
        shdr = ef->e_shdr;
        shstrtab = shdr[ef->shstrindex].sh_addr;

        for (i = 0; i < hdr->e_shnum; i++) {
                if (shdr[i].sh_type != SHT_PROGBITS)
                        continue;
                if (shdr[i].sh_name == 0)
                        continue;
                p = strdupout(shstrtab + shdr[i].sh_name);
                if (strncmp(p, "set_", 4) == 0 && strcmp(p + 4, name) == 0) {
                        *startp = shdr[i].sh_addr;
                        *stopp = shdr[i].sh_addr +  shdr[i].sh_size;
                        *countp = (*stopp - *startp) / sizeof(Elf_Addr);
                        free(p);
                        return (0);
                }
                free(p);
        }

        return (ESRCH);
}

/*
 * Apply any intra-module relocations to the value. p is the load address
 * of the value and val/len is the value to be modified. This does NOT modify
 * the image in-place, because this is done by kern_linker later on.
 */
static int
__elfN(obj_reloc_ptr)(struct preloaded_file *mp, elf_file_t ef, Elf_Addr p,
    void *val, size_t len)
{
        Elf_Ehdr *hdr;
        Elf_Shdr *shdr;
        Elf_Addr off = p;
        Elf_Addr base;
        Elf_Rela a, *abase;
        Elf_Rel r, *rbase;
        int error, i, j, nrel, nrela;

        hdr = &ef->hdr;
        shdr = ef->e_shdr;

        for (i = 0; i < hdr->e_shnum; i++) {
                if (shdr[i].sh_type != SHT_RELA && shdr[i].sh_type != SHT_REL)
                        continue;
                base = shdr[shdr[i].sh_info].sh_addr;
                if (base == 0 || shdr[i].sh_addr == 0)
                        continue;
                if (off < base || off + len > base +
                    shdr[shdr[i].sh_info].sh_size)
                        continue;

                switch (shdr[i].sh_type) {
                case SHT_RELA:
                        abase = (Elf_Rela *)(intptr_t)shdr[i].sh_addr;

                        nrela = shdr[i].sh_size / sizeof(Elf_Rela);
                        for (j = 0; j < nrela; j++) {
                                COPYOUT(abase + j, &a, sizeof(a));

                                error = __elfN(reloc)(ef, __elfN(obj_symaddr),
                                    &a, ELF_RELOC_RELA, base, off, val, len);
                                if (error != 0)
                                        return (error);
                        }
                        break;
                case SHT_REL:
                        rbase = (Elf_Rel *)(intptr_t)shdr[i].sh_addr;

                        nrel = shdr[i].sh_size / sizeof(Elf_Rel);
                        for (j = 0; j < nrel; j++) {
                                COPYOUT(rbase + j, &r, sizeof(r));

                                error = __elfN(reloc)(ef, __elfN(obj_symaddr),
                                    &r, ELF_RELOC_REL, base, off, val, len);
                                if (error != 0)
                                        return (error);
                        }
                        break;
                }
        }
        return (0);
}

/* Look up the address of a specified symbol. */
static Elf_Addr
__elfN(obj_symaddr)(struct elf_file *ef, Elf_Size symidx)
{
        Elf_Sym sym;
        Elf_Addr base;
        int symcnt;

        symcnt = ef->e_shdr[ef->symtabindex].sh_size / sizeof(Elf_Sym);
        if (symidx >= symcnt)
                return (0);
        COPYOUT(ef->e_shdr[ef->symtabindex].sh_addr + symidx * sizeof(Elf_Sym),
            &sym, sizeof(sym));
        if (sym.st_shndx == SHN_UNDEF || sym.st_shndx >= ef->hdr.e_shnum)
                return (0);
        base = ef->e_shdr[sym.st_shndx].sh_addr;
        if (base == 0)
                return (0);
        return (base + sym.st_value);
}