graphene/Pal/src/host/Linux/db_rtld.c

/* -*- mode:c; c-file-style:"k&r"; c-basic-offset: 4; tab-width:4; indent-tabs-mode:nil; mode:auto-fill; fill-column:78; -*- */
/* vim: set ts=4 sw=4 et tw=78 fo=cqt wm=0: */

/* Copyright (C) 2014 OSCAR lab, Stony Brook University
   This file is part of Graphene Library OS.

   Graphene Library OS is free software: you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation, either version 3 of the
   License, or (at your option) any later version.

   Graphene Library OS is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/*
 * db_rtld.c
 *
 * This file contains utilities to load ELF binaries into the memory
 * and link them against each other.
 * The source code in this file is imported and modified from the GNU C
 * Library.
 */

#include "pal_defs.h"
#include "pal_linux_defs.h"
#include "pal.h"
#include "pal_internal.h"
#include "pal_linux.h"
#include "pal_debug.h"
#include "pal_error.h"
#include "pal_security.h"
#include "pal_rtld.h"
#include "api.h"

#include <sysdeps/generic/ldsodefs.h>
#include <elf/elf.h>
#include <bits/dlfcn.h>

#include "elf-x86_64.h"

/* This structure communicates dl state to the debugger.  The debugger
   normally finds it via the DT_DEBUG entry in the dynamic section, but in
   a statically-linked program there is no dynamic section for the debugger
   to examine and it looks for this particular symbol name.  */
struct r_debug pal_r_debug =
        { 1, NULL, (ElfW(Addr)) &pal_dl_debug_state, RT_CONSISTENT, 0 };

extern __typeof(pal_r_debug) _r_debug
    __attribute ((alias ("pal_r_debug")));

/* This function exists solely to have a breakpoint set on it by the
   debugger.  The debugger is supposed to find this function's address by
   examining the r_brk member of struct r_debug, but GDB 4.15 in fact looks
   for this particular symbol name in the PT_INTERP file.  */

/* The special symbol name is set as breakpoint in gdb */
void __attribute__((noinline)) pal_dl_debug_state (void)
{
    if (pal_sec_info._dl_debug_state)
        pal_sec_info._dl_debug_state();
}

extern __typeof(pal_dl_debug_state) _dl_debug_state
    __attribute ((alias ("pal_dl_debug_state")));

void _DkDebugAddMap (struct link_map * map)
{
    struct r_debug * dbg = pal_sec_info._r_debug ? : &pal_r_debug;
    int len = map->l_name ? strlen(map->l_name) + 1 : 0;

    struct link_map ** prev = &dbg->r_map, * last = NULL,
                    * tmp = *prev;
    while (tmp) {
        if (tmp->l_addr == map->l_addr &&
            tmp->l_ld == map->l_ld &&
            !memcmp(tmp->l_name, map->l_name, len))
            return;

        last = tmp;
        tmp = *(prev = &last->l_next);
    }

    struct link_gdb_map * m = malloc(sizeof(struct link_gdb_map) + len);
    if (!m)
        return;

    if (len) {
        m->l_name = (char *) m + sizeof(struct link_gdb_map);
        memcpy((void *) m->l_name, map->l_name, len);
    } else {
        m->l_name = NULL;
    }

    m->l_addr = map->l_addr;
    m->l_ld   = map->l_real_ld;

    dbg->r_state = RT_ADD;
    pal_dl_debug_state();

    *prev = (struct link_map *) m;
    m->l_prev = last;
    m->l_next = NULL;

    dbg->r_state = RT_CONSISTENT;
    pal_dl_debug_state();
}

void _DkDebugDelMap (struct link_map * map)
{
    struct r_debug * dbg = pal_sec_info._r_debug ? : &pal_r_debug;
    int len = map->l_name ? strlen(map->l_name) + 1 : 0;

    struct link_map ** prev = &dbg->r_map, * last = NULL,
                    * tmp = *prev, * found = NULL;
    while (tmp) {
        if (tmp->l_addr == map->l_addr &&
            tmp->l_ld == map->l_ld &&
            !memcmp(tmp->l_name, map->l_name, len)) {
            found = tmp;
            break;
        }

        last = tmp;
        tmp = *(prev = &last->l_next);
    }

    if (!found)
        return;

    dbg->r_state = RT_DELETE;
    pal_dl_debug_state();

    if (last)
        last->l_next = tmp->l_next;
    else
        dbg->r_map = tmp->l_next;

    if (tmp->l_next)
        tmp->l_next->l_prev = last;

    free(tmp);

    dbg->r_state = RT_CONSISTENT;
    pal_dl_debug_state();
}

extern void setup_elf_hash (struct link_map *map);

void setup_pal_map (const char * realname, ElfW(Dyn) ** dyn, ElfW(Addr) addr)
{
    assert (loaded_libraries == NULL);

    const ElfW(Ehdr) * header = (void *) addr;
    struct link_map * l = new_elf_object(realname, OBJECT_RTLD);
    memcpy(l->l_info, dyn, sizeof(l->l_info));
    l->l_real_ld = l->l_ld = (void *) elf_machine_dynamic();
    l->l_addr  = addr;
    l->l_entry = header->e_entry;
    l->l_phdr  = (void *) (addr + header->e_phoff);
    l->l_phnum = header->e_phnum;
    l->l_relocated = true;
    l->l_lookup_symbol = true;
    l->l_soname = "libpal.so";
    l->l_text_start = (ElfW(Addr)) &text_start;
    l->l_text_end   = (ElfW(Addr)) &text_end;
    l->l_data_start = (ElfW(Addr)) &data_start;
    l->l_data_end   = (ElfW(Addr)) &data_end;
    setup_elf_hash(l);

    void * begin_hole = (void *) ALLOC_ALIGNUP(l->l_text_end);
    void * end_hole = (void *) ALLOC_ALIGNDOWN(l->l_data_start);

    /* Usually the test segment and data segment of a loaded library has
       a gap between them. Need to fill the hole with a empty area */
    if (begin_hole < end_hole) {
        void * addr = begin_hole;
        _DkVirtualMemoryAlloc(&addr, end_hole - begin_hole,
                              PAL_ALLOC_RESERVE, PAL_PROT_NONE);
    }

    /* Set up debugging before the debugger is notified for the first time.  */
    if (l->l_info[DT_DEBUG] != NULL)
        l->l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) &pal_r_debug;

    l->l_prev = l->l_next = NULL;
    loaded_libraries = l;

    _DkDebugAddMap(l);
}

#if USE_VDSO_GETTIME == 1
void setup_vdso_map (ElfW(Addr) addr)
{
    const ElfW(Ehdr) * header = (void *) addr;
    struct link_map * l = new_elf_object("vdso", OBJECT_RTLD);

    l->l_addr  = addr;
    l->l_entry = header->e_entry;
    l->l_phdr  = (void *) (addr + header->e_phoff);
    l->l_phnum = header->e_phnum;
    l->l_relocated = true;
    l->l_soname = "libpal.so";

    ElfW(Addr) load_offset = 0;
    const ElfW(Phdr) * ph;
    for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
        switch (ph->p_type) {
            case PT_LOAD:
                load_offset = addr + (ElfW(Addr)) ph->p_offset
                              - (ElfW(Addr)) ph->p_vaddr;
                break;
            case PT_DYNAMIC:
                l->l_real_ld = l->l_ld = (void *) addr + ph->p_offset;
                l->l_ldnum = ph->p_memsz / sizeof (ElfW(Dyn));
                break;
        }

    ElfW(Dyn) local_dyn[4];
    int ndyn = 0;
    ElfW(Dyn) * dyn;
    for (dyn = l->l_ld ; dyn < &l->l_ld[l->l_ldnum]; ++dyn)
        switch(dyn->d_tag) {
            case DT_STRTAB:
            case DT_SYMTAB:
                local_dyn[ndyn] = *dyn;
                local_dyn[ndyn].d_un.d_ptr += load_offset;
                l->l_info[dyn->d_tag] = &local_dyn[ndyn++];
                break;
            case DT_HASH: {
                ElfW(Word) * h = (ElfW(Word) *) (D_PTR(dyn) + load_offset);
                l->l_nbuckets = h[0];
                l->l_buckets  = &h[2];
                l->l_chain    = &h[l->l_nbuckets + 2];
                break;
            }
            case DT_VERSYM:
            case DT_VERDEF:
                local_dyn[ndyn] = *dyn;
                local_dyn[ndyn].d_un.d_ptr += load_offset;
                l->l_info[VERSYMIDX(dyn->d_tag)] = &local_dyn[ndyn++];
                break;
        }

#if USE_CLOCK_GETTIME == 1
    const char * gettime = "__vdso_clock_gettime";
#else
    const char * gettime = "__vdso_gettimeofday";
#endif
    uint_fast32_t fast_hash = elf_fast_hash(gettime);
    long int hash = elf_hash(gettime);
    ElfW(Sym) * sym = NULL;

    sym = do_lookup_map(NULL, gettime, fast_hash, hash, l);
    if (sym)
#if USE_CLOCK_GETTIME == 1
        __vdso_clock_gettime =
#else
        __vdso_gettimeofday =
#endif
                (void *) (load_offset + sym->st_value);

    free(l);
}
#endif

ElfW(Addr) resolve_rtld (const char * sym_name)
{
    /* We are not using this, because in Linux we can rely on
       rtld_map to directly lookup symbols */
    return 0;
}