The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/amd64/amd64/elf_machdep.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright 1996-1998 John D. Polstra.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   26  */
   27 
   28 #include <sys/cdefs.h>
   29 __FBSDID("$FreeBSD: stable/12/sys/amd64/amd64/elf_machdep.c 345067 2019-03-12 16:33:44Z kib $");
   30 
   31 #include <sys/param.h>
   32 #include <sys/kernel.h>
   33 #include <sys/systm.h>
   34 #include <sys/exec.h>
   35 #include <sys/imgact.h>
   36 #include <sys/linker.h>
   37 #include <sys/proc.h>
   38 #include <sys/sysent.h>
   39 #include <sys/imgact_elf.h>
   40 #include <sys/syscall.h>
   41 #include <sys/signalvar.h>
   42 #include <sys/vnode.h>
   43 
   44 #include <vm/vm.h>
   45 #include <vm/pmap.h>
   46 #include <vm/vm_param.h>
   47 
   48 #include <machine/elf.h>
   49 #include <machine/fpu.h>
   50 #include <machine/md_var.h>
   51 
   52 struct sysentvec elf64_freebsd_sysvec = {
   53         .sv_size        = SYS_MAXSYSCALL,
   54         .sv_table       = sysent,
   55         .sv_mask        = 0,
   56         .sv_errsize     = 0,
   57         .sv_errtbl      = NULL,
   58         .sv_transtrap   = NULL,
   59         .sv_fixup       = __elfN(freebsd_fixup),
   60         .sv_sendsig     = sendsig,
   61         .sv_sigcode     = sigcode,
   62         .sv_szsigcode   = &szsigcode,
   63         .sv_name        = "FreeBSD ELF64",
   64         .sv_coredump    = __elfN(coredump),
   65         .sv_imgact_try  = NULL,
   66         .sv_minsigstksz = MINSIGSTKSZ,
   67         .sv_pagesize    = PAGE_SIZE,
   68         .sv_minuser     = VM_MIN_ADDRESS,
   69         .sv_maxuser     = VM_MAXUSER_ADDRESS,
   70         .sv_usrstack    = USRSTACK,
   71         .sv_psstrings   = PS_STRINGS,
   72         .sv_stackprot   = VM_PROT_ALL,
   73         .sv_copyout_strings     = exec_copyout_strings,
   74         .sv_setregs     = exec_setregs,
   75         .sv_fixlimit    = NULL,
   76         .sv_maxssiz     = NULL,
   77         .sv_flags       = SV_ABI_FREEBSD | SV_ASLR | SV_LP64 | SV_SHP |
   78                             SV_TIMEKEEP,
   79         .sv_set_syscall_retval = cpu_set_syscall_retval,
   80         .sv_fetch_syscall_args = cpu_fetch_syscall_args,
   81         .sv_syscallnames = syscallnames,
   82         .sv_shared_page_base = SHAREDPAGE,
   83         .sv_shared_page_len = PAGE_SIZE,
   84         .sv_schedtail   = NULL,
   85         .sv_thread_detach = NULL,
   86         .sv_trap        = NULL,
   87 };
   88 INIT_SYSENTVEC(elf64_sysvec, &elf64_freebsd_sysvec);
   89 
   90 void
   91 amd64_lower_shared_page(struct sysentvec *sv)
   92 {
   93         if (hw_lower_amd64_sharedpage != 0) {
   94                 sv->sv_maxuser -= PAGE_SIZE;
   95                 sv->sv_shared_page_base -= PAGE_SIZE;
   96                 sv->sv_usrstack -= PAGE_SIZE;
   97                 sv->sv_psstrings -= PAGE_SIZE;
   98         }
   99 }
  100 
  101 /*
  102  * Do this fixup before INIT_SYSENTVEC (SI_ORDER_ANY) because the latter
  103  * uses the value of sv_shared_page_base.
  104  */
  105 SYSINIT(elf64_sysvec_fixup, SI_SUB_EXEC, SI_ORDER_FIRST,
  106         (sysinit_cfunc_t) amd64_lower_shared_page,
  107         &elf64_freebsd_sysvec);
  108 
  109 static Elf64_Brandinfo freebsd_brand_info = {
  110         .brand          = ELFOSABI_FREEBSD,
  111         .machine        = EM_X86_64,
  112         .compat_3_brand = "FreeBSD",
  113         .emul_path      = NULL,
  114         .interp_path    = "/libexec/ld-elf.so.1",
  115         .sysvec         = &elf64_freebsd_sysvec,
  116         .interp_newpath = NULL,
  117         .brand_note     = &elf64_freebsd_brandnote,
  118         .flags          = BI_CAN_EXEC_DYN | BI_BRAND_NOTE
  119 };
  120 
  121 SYSINIT(elf64, SI_SUB_EXEC, SI_ORDER_FIRST,
  122         (sysinit_cfunc_t) elf64_insert_brand_entry,
  123         &freebsd_brand_info);
  124 
  125 static Elf64_Brandinfo freebsd_brand_oinfo = {
  126         .brand          = ELFOSABI_FREEBSD,
  127         .machine        = EM_X86_64,
  128         .compat_3_brand = "FreeBSD",
  129         .emul_path      = NULL,
  130         .interp_path    = "/usr/libexec/ld-elf.so.1",
  131         .sysvec         = &elf64_freebsd_sysvec,
  132         .interp_newpath = NULL,
  133         .brand_note     = &elf64_freebsd_brandnote,
  134         .flags          = BI_CAN_EXEC_DYN | BI_BRAND_NOTE
  135 };
  136 
  137 SYSINIT(oelf64, SI_SUB_EXEC, SI_ORDER_ANY,
  138         (sysinit_cfunc_t) elf64_insert_brand_entry,
  139         &freebsd_brand_oinfo);
  140 
  141 static Elf64_Brandinfo kfreebsd_brand_info = {
  142         .brand          = ELFOSABI_FREEBSD,
  143         .machine        = EM_X86_64,
  144         .compat_3_brand = "FreeBSD",
  145         .emul_path      = NULL,
  146         .interp_path    = "/lib/ld-kfreebsd-x86-64.so.1",
  147         .sysvec         = &elf64_freebsd_sysvec,
  148         .interp_newpath = NULL,
  149         .brand_note     = &elf64_kfreebsd_brandnote,
  150         .flags          = BI_CAN_EXEC_DYN | BI_BRAND_NOTE_MANDATORY
  151 };
  152 
  153 SYSINIT(kelf64, SI_SUB_EXEC, SI_ORDER_ANY,
  154         (sysinit_cfunc_t) elf64_insert_brand_entry,
  155         &kfreebsd_brand_info);
  156 
  157 void
  158 elf64_dump_thread(struct thread *td, void *dst, size_t *off)
  159 {
  160         void *buf;
  161         size_t len;
  162 
  163         len = 0;
  164         if (use_xsave) {
  165                 if (dst != NULL) {
  166                         fpugetregs(td);
  167                         len += elf64_populate_note(NT_X86_XSTATE,
  168                             get_pcb_user_save_td(td), dst,
  169                             cpu_max_ext_state_size, &buf);
  170                         *(uint64_t *)((char *)buf + X86_XSTATE_XCR0_OFFSET) =
  171                             xsave_mask;
  172                 } else
  173                         len += elf64_populate_note(NT_X86_XSTATE, NULL, NULL,
  174                             cpu_max_ext_state_size, NULL);
  175         }
  176         *off = len;
  177 }
  178 
  179 bool
  180 elf_is_ifunc_reloc(Elf_Size r_info)
  181 {
  182 
  183         return (ELF_R_TYPE(r_info) == R_X86_64_IRELATIVE);
  184 }
  185 
  186 /* Process one elf relocation with addend. */
  187 static int
  188 elf_reloc_internal(linker_file_t lf, Elf_Addr relocbase, const void *data,
  189     int type, elf_lookup_fn lookup)
  190 {
  191         Elf64_Addr *where, val;
  192         Elf32_Addr *where32, val32;
  193         Elf_Addr addr;
  194         Elf_Addr addend;
  195         Elf_Size rtype, symidx;
  196         const Elf_Rel *rel;
  197         const Elf_Rela *rela;
  198         int error;
  199 
  200         switch (type) {
  201         case ELF_RELOC_REL:
  202                 rel = (const Elf_Rel *)data;
  203                 where = (Elf_Addr *) (relocbase + rel->r_offset);
  204                 rtype = ELF_R_TYPE(rel->r_info);
  205                 symidx = ELF_R_SYM(rel->r_info);
  206                 /* Addend is 32 bit on 32 bit relocs */
  207                 switch (rtype) {
  208                 case R_X86_64_PC32:
  209                 case R_X86_64_32S:
  210                 case R_X86_64_PLT32:
  211                         addend = *(Elf32_Addr *)where;
  212                         break;
  213                 default:
  214                         addend = *where;
  215                         break;
  216                 }
  217                 break;
  218         case ELF_RELOC_RELA:
  219                 rela = (const Elf_Rela *)data;
  220                 where = (Elf_Addr *) (relocbase + rela->r_offset);
  221                 addend = rela->r_addend;
  222                 rtype = ELF_R_TYPE(rela->r_info);
  223                 symidx = ELF_R_SYM(rela->r_info);
  224                 break;
  225         default:
  226                 panic("unknown reloc type %d\n", type);
  227         }
  228 
  229         switch (rtype) {
  230                 case R_X86_64_NONE:     /* none */
  231                         break;
  232 
  233                 case R_X86_64_64:               /* S + A */
  234                         error = lookup(lf, symidx, 1, &addr);
  235                         val = addr + addend;
  236                         if (error != 0)
  237                                 return -1;
  238                         if (*where != val)
  239                                 *where = val;
  240                         break;
  241 
  242                 case R_X86_64_PC32:     /* S + A - P */
  243                 case R_X86_64_PLT32:    /* L + A - P, L is PLT location for
  244                                            the symbol, which we treat as S */
  245                         error = lookup(lf, symidx, 1, &addr);
  246                         where32 = (Elf32_Addr *)where;
  247                         val32 = (Elf32_Addr)(addr + addend - (Elf_Addr)where);
  248                         if (error != 0)
  249                                 return -1;
  250                         if (*where32 != val32)
  251                                 *where32 = val32;
  252                         break;
  253 
  254                 case R_X86_64_32S:      /* S + A sign extend */
  255                         error = lookup(lf, symidx, 1, &addr);
  256                         val32 = (Elf32_Addr)(addr + addend);
  257                         where32 = (Elf32_Addr *)where;
  258                         if (error != 0)
  259                                 return -1;
  260                         if (*where32 != val32)
  261                                 *where32 = val32;
  262                         break;
  263 
  264                 case R_X86_64_COPY:     /* none */
  265                         /*
  266                          * There shouldn't be copy relocations in kernel
  267                          * objects.
  268                          */
  269                         printf("kldload: unexpected R_COPY relocation\n");
  270                         return (-1);
  271                         break;
  272 
  273                 case R_X86_64_GLOB_DAT: /* S */
  274                 case R_X86_64_JMP_SLOT: /* XXX need addend + offset */
  275                         error = lookup(lf, symidx, 1, &addr);
  276                         if (error != 0)
  277                                 return -1;
  278                         if (*where != addr)
  279                                 *where = addr;
  280                         break;
  281 
  282                 case R_X86_64_RELATIVE: /* B + A */
  283                         addr = relocbase + addend;
  284                         val = addr;
  285                         if (*where != val)
  286                                 *where = val;
  287                         break;
  288 
  289                 case R_X86_64_IRELATIVE:
  290                         addr = relocbase + addend;
  291                         val = ((Elf64_Addr (*)(void))addr)();
  292                         if (*where != val)
  293                                 *where = val;
  294                         break;
  295 
  296                 default:
  297                         printf("kldload: unexpected relocation type %ld\n",
  298                                rtype);
  299                         return (-1);
  300         }
  301         return (0);
  302 }
  303 
  304 int
  305 elf_reloc(linker_file_t lf, Elf_Addr relocbase, const void *data, int type,
  306     elf_lookup_fn lookup)
  307 {
  308 
  309         return (elf_reloc_internal(lf, relocbase, data, type, lookup));
  310 }
  311 
  312 int
  313 elf_reloc_local(linker_file_t lf, Elf_Addr relocbase, const void *data,
  314     int type, elf_lookup_fn lookup)
  315 {
  316 
  317         return (elf_reloc_internal(lf, relocbase, data, type, lookup));
  318 }
  319 
  320 int
  321 elf_cpu_load_file(linker_file_t lf __unused)
  322 {
  323 
  324         return (0);
  325 }
  326 
  327 int
  328 elf_cpu_unload_file(linker_file_t lf __unused)
  329 {
  330 
  331         return (0);
  332 }

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