path: root/other/burneye/tmp/dl_libv2.c

/*
 * Copyright the grugq, 2001.
 */

#include <linux/types.h>
#include <asm/unistd.h>
#include <linux/fcntl.h>
#include <linux/mman.h>
#include <linux/dirent.h>

#include "dl_libv2.h"


static void * lib_open(const char *lib_name, void *head, void *handle);

inline __syscall1(int, close, int, fd);
inline __syscall3(int, open, const char *, file, int, flag, int, mode);
inline __syscall3(ssize_t, read, int, fd, void *, buf, size_t, count);
inline __syscall3(ssize_t, write, int, fd, const void *, buf, size_t, count);

/* 
 * Elf hash function from the ABI.
 */
static unsigned long
elf_hash(const unsigned char *name)
{
        unsigned long   h = 0,
                        g;
        
        while (*name) {
                h = (h << 4) + *name++;
                if ((g = h & 0xf0000000))
                        h ^= g >> 24;
                h &= ~g;
        }
        return h;
}

/* 
 * turn a string (i.e. "0401b000") into a pointer
 */
static void *
my_strtop(unsigned char *str, char **end)
{
        register unsigned char    c,
                                 *s;
        register long             r = 0;

        s = str;
        for (c = *s; c != '\0'; c = *s++) {
                /* based on ASCII table order ;) */
                if ((c >= '0') && (c <= '9'))
                        c -= '0';
                else if ((c >= 'A') && (c <= 'F'))
                        c = (c - 'A') + 10;
                else if ((c >= 'a') && (c <= 'f'))
                        c = (c - 'a') + 10;
                else
                        break;
                r *= 16;
                r += c;
        }
        if (end)
                *end = s;
        return (void *)r;
}

/*
 * a simplistic non optimized strncmp(3)
 */
static int
my_strncmp(const char *s, const char *t, int len)
{
        register int i;

        for (i = 0; (*s == *t) && (i <= len); s++, t++, i++)
                if ((*s == '\0') || (i == len))
                        return 0;
        return *s - *t;
}

static void *
add_node(LibDesc *head, LibDesc *ld)
{
        int         f = 0;
        char        name[7];
        LibDesc   * ret,
                  * n;

        if (!head) {
                f = 1;
                head = ld;
                head->l_prev = NULL;

                name[0] = 'm';
                name[1] = 'a';
                name[2] = 'l';
                name[3] = 'l';
                name[4] = 'o';
                name[5] = 'c';
                name[6] = 0;

                if ((head->malloc = dl_lib_sym(name, head)) == NULL)
                        return NULL;
        }
        else
                while (head->l_prev)
                        head = head->l_prev;

        if ((ret = head->malloc(sizeof (LibDesc))) == NULL)
                return NULL;

        /* -O will make this inline asm... */
        memcpy(ret, ld, sizeof(LibDesc));

        n = head;
        while (n->l_next)
                n = n->l_next;

        n->l_next = ret;
        /* ugly hack to save the head of the list */
        if (!f)
                ret->l_prev = n;
        ret->l_next = NULL;

        return ret;
}

static void *
lib_open(const char *lib_name, void *head, void *lib_handle)
{
        int               fd,
                          nread,
                          i;
        char              name[16],     /* name buffer */
                          buf[BUFSIZ * 2],      /* read buffer */
                        * text_start = NULL,    /* store for the .text addr */
                        * p,    /* walking pointer */
                        * q,    /* standing pointer */
                        * s;    /* store for strcmp() */
        Elf32_Ehdr      * ehdr;
        Elf32_Phdr      * phdr;
        Elf32_Dyn       * dyn;
        LibDesc         * libd;

        /* enable pointer semantics */
        libd = alloca(sizeof(LibDesc));
        memset(libd, 0x00, sizeof(LibDesc));
        
        /* wish there was a cleaner way of not using .rodata... :-/ */
        /*    actually there is, using a few shifts to make an int of 
         *    every four char's then assigning that to a walking int ptr*/
        name[ 0] = '/';
        name[ 1] = 'p';
        name[ 2] = 'r';
        name[ 3] = 'o';
        name[ 4] = 'c';
        name[ 5] = '/';
        name[ 6] = 's';
        name[ 7] = 'e';
        name[ 8] = 'l';
        name[ 9] = 'f';
        name[10] = '/';
        name[11] = 'm';
        name[12] = 'a';
        name[13] = 'p';
        name[14] = 's';
        name[15] = '\0';

        if ((fd = _open(name, O_RDONLY, 0)) <0)
                return NULL;

        /* memset becomes inline ASM with -O */
        memset(buf, 0x00, sizeof(buf));

        /* we read because we can't mmap(2) /proc... */
        if ((nread = _read(fd, buf, sizeof buf)) < 0)
                return NULL;
        /* tidy up, need to leave the exec's environment as clean as possible */
        (void)_close(fd);

        /* 
         * here begins the hairy algo.
         *
         * We parse out a line of /proc/self/maps 
         * then we check to see if it is our library, if it is, then we
         * need to save pointers to its .text string...
         * 
         * later we can parse the string and determine pointers..
         */
        for (i=0; i < nread; i++) {
                int     in_lib = 0;

                s = q = buf + i;
                /* find end of string without walking off the stack... */
                while ((*q != '\n') && (*q != '\0') && (i < nread)) {
                        q++;
                        i++;
                }
                *q = 0x00;      /* terminate the string, for debugging */

                /* check to see if we match the string */
                for (p = q; (p > s) && (*p != ' '); p--) {
                        if (! my_strncmp(lib_name, p, strlen(lib_name)-1)) {
                                in_lib = 1;
                                break;
                        }
                }

                /*  accounting is all updated, so just try again... */
                if (!in_lib)
                        continue;

                /* seek past the '04xxx-04xxx' to the first space */
                for (p = s; (p < q) && (*p != ' '); p++) 
                        ;
                /* point to the protection string */
                p++;

                /* determine if we are looking at a .text segment,
                 * or a .data segment... */
                if ((p[0] == 'r') && (p[1] == '-') && (p[2] == 'x'))
                        text_start = s;
                else 
                        ;

                /* if we got what we come for, piss off */
                if (text_start)
                        break;
        }

        /* the .data segment has the PT_DYNAMIC and has to follow the .text
         * segment.  This is a "feature", rather than a hard and fast rule, but
         * it is reliable enough for almost all cases. This need not be true
         * for PIC code (as in a library) and that bastard the owl might go
         * and make this very annoying, but I don't think that is enough of
         * an incentive to alter this code.
         *
         * It is, of course, quite trivial to add support for searching for the
         * .data, in fact I have taken code out which did just that.  The code
         * was not needed and I felt it more imporant that this code be clear,
         * rather than comprehensive.
         *
         * It is sufficient for now.
         *
         * the .text segment has the elf and program headers, and the .data
         * should follow immediatly afterwards.  The .data will have the
         * dynamic linkage pointers so we can locate the hash table, string
         * table, etc. etc.
         */

        libd->l_load_addr = my_strtop(text_start, &p); 

        ehdr =(Elf32_Ehdr *) libd->l_load_addr;
        phdr =(Elf32_Phdr *)(libd->l_load_addr + ehdr->e_phoff);

        while (phdr->p_type != PT_DYNAMIC)
                phdr++;

        /* the .dynamic is in the .data segment, but we can just use the
         * load address to locate it in memory.  non-portable? */
        /* The correct way to do this is to use p_offset and p_align to
         * calculate the location of the start of the .data and .dynamic
         * segments... but this way works quite nicely */
        dyn  = (Elf32_Dyn *) (libd->l_load_addr + phdr->p_vaddr);

        /* 
         * I can't understand why l_hash needs the load_addr added to it, 
         * and the other locations don't.  It seems they are intialized
         * by the rtdl and DT_HASH isn't; but I can't say for sure...
         */
        for (; dyn->d_tag != DT_NULL; dyn++) {
		/* in retrospect this should have been a switch(). doh! */
                if (dyn->d_tag == DT_HASH)
                        libd->l_buckets = (void *)((long)dyn->d_un.d_ptr +
                                        (long)libd->l_load_addr);
                else if (dyn->d_tag == DT_SYMTAB)
                        libd->l_symtab = (void *)dyn->d_un.d_ptr;
                else if (dyn->d_tag == DT_STRTAB)
                        libd->l_strtab = (void *)dyn->d_un.d_ptr;
                else
                        continue;
        }

        libd->l_nbuckets = *libd->l_buckets++;
        libd->l_nchain   = *libd->l_buckets++;
        libd->l_chain    = &(libd->l_buckets[libd->l_nbuckets]);

        libd->l_handle = lib_handle;

        return (add_node(head, libd));
}

void *
dl_lib_init(void)
{
        char    name[10];
        LibDesc *head;

        name[0] = '/';
        name[1] = 'l';
        name[2] = 'i';
        name[3] = 'b';
        name[4] = 'c';
        name[5] = '-';
        name[6] =  0;

        if ((head =(LibDesc *)lib_open(name, NULL, NULL)) == NULL)
                return NULL;
        /* we resolve almost all of the functions we will need right here,
         * this will save some execution time for apps which do multiple 
         * dl_lib_open()s... 
         *
         * The penalty for code which only does a single dl_lib_init() is 
         * minimal, so I don't mind this sacrifice.
         *
         * The only thing that needs to be pointed out is that this is not OOP.
         * Don't even think about accusing me of that malarky. 
         */

        name[0] = 'f';
        name[1] = 'r';
        name[2] = 'e';
        name[3] = 'e';
        name[4] =  0;

        if ((head->free = dl_lib_sym(name, head)) == NULL)
                return NULL;

        name[0] = '_';
        name[1] = 'd';
        name[2] = 'l';
        name[3] = '_';
        name[4] = 'o';
        name[5] = 'p';
        name[6] = 'e';
        name[7] = 'n';
        name[8] =  0;

        if ((head->dlopen = dl_lib_sym(name, head)) == NULL)
                return NULL;

        name[0] = '_';
        name[1] = 'd';
        name[2] = 'l';
        name[3] = '_';
        name[4] = 'c';
        name[5] = 'l';
        name[6] = 'o';
        name[7] = 's';
        name[8] = 'e';
        name[9] =  0;
        
        if ((head->dlclose = dl_lib_sym(name, head)) == NULL)
                return NULL;

        return ((void *)head);
}

void
dl_lib_fini(void *h)
{
        LibDesc         *head,
                        *node;

        head = (LibDesc *)h;

        if (!head)
                return;

        while (head->l_prev)
                head = head->l_prev;

        /* seek the tail of the list */
        for (node = head; node->l_next; node = node->l_next)
                ;

        /* walk up backwards, closing everything */
        for (; node; node = node->l_prev)
                dl_lib_close(node, head);

        /* it should all be done */
        return;
}

void
dl_lib_close(void *l, void *h)
{
        LibDesc         *head,
                        *fn, 
                        *bn,
                        *ld;

        ld = (LibDesc *)l;
        head = (LibDesc *)h;
        if (!ld || !h)
                return;

        while (head->l_prev)
                head = head->l_prev;

        /* if we have a dlopen() handle, we can close it */
        if (ld->l_handle)
                head->dlclose(ld->l_handle);

        bn = ld->l_prev;
        fn = ld->l_next;

        /* iff we aren't the head of the list, then we need to remove ourselves
         * and fix up the list:
         *
         * iff there is a previous node, point it to our l_next
         * iff there is a next node, point it to our l_prev
         * */
        if (bn)
                bn->l_next = fn;
        if (fn) 
                fn->l_prev = bn;

        head->free(ld);
        ld = NULL;      /* prevent silliness */

        return;
}

void *
dl_lib_open(char *lib_name, void *h)
{
        int       foo = 1;
        void    * handle;
        LibDesc * head;

        head = (LibDesc *)h;

        if (!lib_name || !head)
                return NULL;

        /* seek the head of the linked list */
        while (head->l_prev)
                head = head->l_prev;

        if ((handle = head->dlopen(lib_name, 1, __builtin_return_address(0)))
                        == NULL)
                return NULL;
        /* we have successfully mapped the library into our space, now
         * all we need to do is intialize our usual LibDesc for it */
        return (lib_open(lib_name, head, handle));
}


void *
dl_lib_sym(char *sym_name, void *handler)
{
        Elf32_Sym       * sym,
                        * symtab;
        int               hn,
                          ndx;
        char            * strs;
        LibDesc         * libd = (LibDesc *)handler;
        
        if (!sym_name || !libd)
                return NULL;

        strs = libd->l_strtab;
        symtab = libd->l_symtab;

        hn = elf_hash(sym_name) % libd->l_nbuckets;

        /* we need to "follow the chain" until we find our function... */
        for (ndx = libd->l_buckets[hn]; ndx; ndx = libd->l_chain[ndx]) {
                sym = symtab + ndx;

                if ((ELF32_ST_TYPE(sym->st_info) == STT_FUNC) &&
                        (!my_strncmp(strs + sym->st_name, sym_name,
                                     strlen(sym_name) - 1))) {
                        /* we found it! rejoice the king has cum. */
                        return ((void *)((long)sym->st_value +
                                                (long)libd->l_load_addr));
                }
        }

        /* we have totally bombed out.  There is no symbol by that name in the
         * symtab... sorry :-( */
        return NULL;
}