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: head/sys/amd64/amd64/elf_machdep.c 344705 2019-03-01 16:16:38Z trasz $");
   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_errsize     = 0,
   56         .sv_errtbl      = NULL,
   57         .sv_transtrap   = NULL,
   58         .sv_fixup       = __elfN(freebsd_fixup),
   59         .sv_sendsig     = sendsig,
   60         .sv_sigcode     = sigcode,
   61         .sv_szsigcode   = &szsigcode,
   62         .sv_name        = "FreeBSD ELF64",
   63         .sv_coredump    = __elfN(coredump),
   64         .sv_imgact_try  = NULL,
   65         .sv_minsigstksz = MINSIGSTKSZ,
   66         .sv_minuser     = VM_MIN_ADDRESS,
   67         .sv_maxuser     = VM_MAXUSER_ADDRESS,
   68         .sv_usrstack    = USRSTACK,
   69         .sv_psstrings   = PS_STRINGS,
   70         .sv_stackprot   = VM_PROT_ALL,
   71         .sv_copyout_strings     = exec_copyout_strings,
   72         .sv_setregs     = exec_setregs,
   73         .sv_fixlimit    = NULL,
   74         .sv_maxssiz     = NULL,
   75         .sv_flags       = SV_ABI_FREEBSD | SV_ASLR | SV_LP64 | SV_SHP |
   76                             SV_TIMEKEEP,
   77         .sv_set_syscall_retval = cpu_set_syscall_retval,
   78         .sv_fetch_syscall_args = cpu_fetch_syscall_args,
   79         .sv_syscallnames = syscallnames,
   80         .sv_shared_page_base = SHAREDPAGE,
   81         .sv_shared_page_len = PAGE_SIZE,
   82         .sv_schedtail   = NULL,
   83         .sv_thread_detach = NULL,
   84         .sv_trap        = NULL,
   85 };
   86 INIT_SYSENTVEC(elf64_sysvec, &elf64_freebsd_sysvec);
   87 
   88 void
   89 amd64_lower_shared_page(struct sysentvec *sv)
   90 {
   91         if (hw_lower_amd64_sharedpage != 0) {
   92                 sv->sv_maxuser -= PAGE_SIZE;
   93                 sv->sv_shared_page_base -= PAGE_SIZE;
   94                 sv->sv_usrstack -= PAGE_SIZE;
   95                 sv->sv_psstrings -= PAGE_SIZE;
   96         }
   97 }
   98 
   99 /*
  100  * Do this fixup before INIT_SYSENTVEC (SI_ORDER_ANY) because the latter
  101  * uses the value of sv_shared_page_base.
  102  */
  103 SYSINIT(elf64_sysvec_fixup, SI_SUB_EXEC, SI_ORDER_FIRST,
  104         (sysinit_cfunc_t) amd64_lower_shared_page,
  105         &elf64_freebsd_sysvec);
  106 
  107 static Elf64_Brandinfo freebsd_brand_info = {
  108         .brand          = ELFOSABI_FREEBSD,
  109         .machine        = EM_X86_64,
  110         .compat_3_brand = "FreeBSD",
  111         .emul_path      = NULL,
  112         .interp_path    = "/libexec/ld-elf.so.1",
  113         .sysvec         = &elf64_freebsd_sysvec,
  114         .interp_newpath = NULL,
  115         .brand_note     = &elf64_freebsd_brandnote,
  116         .flags          = BI_CAN_EXEC_DYN | BI_BRAND_NOTE
  117 };
  118 
  119 SYSINIT(elf64, SI_SUB_EXEC, SI_ORDER_FIRST,
  120         (sysinit_cfunc_t) elf64_insert_brand_entry,
  121         &freebsd_brand_info);
  122 
  123 static Elf64_Brandinfo freebsd_brand_oinfo = {
  124         .brand          = ELFOSABI_FREEBSD,
  125         .machine        = EM_X86_64,
  126         .compat_3_brand = "FreeBSD",
  127         .emul_path      = NULL,
  128         .interp_path    = "/usr/libexec/ld-elf.so.1",
  129         .sysvec         = &elf64_freebsd_sysvec,
  130         .interp_newpath = NULL,
  131         .brand_note     = &elf64_freebsd_brandnote,
  132         .flags          = BI_CAN_EXEC_DYN | BI_BRAND_NOTE
  133 };
  134 
  135 SYSINIT(oelf64, SI_SUB_EXEC, SI_ORDER_ANY,
  136         (sysinit_cfunc_t) elf64_insert_brand_entry,
  137         &freebsd_brand_oinfo);
  138 
  139 static Elf64_Brandinfo kfreebsd_brand_info = {
  140         .brand          = ELFOSABI_FREEBSD,
  141         .machine        = EM_X86_64,
  142         .compat_3_brand = "FreeBSD",
  143         .emul_path      = NULL,
  144         .interp_path    = "/lib/ld-kfreebsd-x86-64.so.1",
  145         .sysvec         = &elf64_freebsd_sysvec,
  146         .interp_newpath = NULL,
  147         .brand_note     = &elf64_kfreebsd_brandnote,
  148         .flags          = BI_CAN_EXEC_DYN | BI_BRAND_NOTE_MANDATORY
  149 };
  150 
  151 SYSINIT(kelf64, SI_SUB_EXEC, SI_ORDER_ANY,
  152         (sysinit_cfunc_t) elf64_insert_brand_entry,
  153         &kfreebsd_brand_info);
  154 
  155 void
  156 elf64_dump_thread(struct thread *td, void *dst, size_t *off)
  157 {
  158         void *buf;
  159         size_t len;
  160 
  161         len = 0;
  162         if (use_xsave) {
  163                 if (dst != NULL) {
  164                         fpugetregs(td);
  165                         len += elf64_populate_note(NT_X86_XSTATE,
  166                             get_pcb_user_save_td(td), dst,
  167                             cpu_max_ext_state_size, &buf);
  168                         *(uint64_t *)((char *)buf + X86_XSTATE_XCR0_OFFSET) =
  169                             xsave_mask;
  170                 } else
  171                         len += elf64_populate_note(NT_X86_XSTATE, NULL, NULL,
  172                             cpu_max_ext_state_size, NULL);
  173         }
  174         *off = len;
  175 }
  176 
  177 bool
  178 elf_is_ifunc_reloc(Elf_Size r_info)
  179 {
  180 
  181         return (ELF_R_TYPE(r_info) == R_X86_64_IRELATIVE);
  182 }
  183 
  184 /* Process one elf relocation with addend. */
  185 static int
  186 elf_reloc_internal(linker_file_t lf, Elf_Addr relocbase, const void *data,
  187     int type, elf_lookup_fn lookup)
  188 {
  189         Elf64_Addr *where, val;
  190         Elf32_Addr *where32, val32;
  191         Elf_Addr addr;
  192         Elf_Addr addend;
  193         Elf_Size rtype, symidx;
  194         const Elf_Rel *rel;
  195         const Elf_Rela *rela;
  196         int error;
  197 
  198         switch (type) {
  199         case ELF_RELOC_REL:
  200                 rel = (const Elf_Rel *)data;
  201                 where = (Elf_Addr *) (relocbase + rel->r_offset);
  202                 rtype = ELF_R_TYPE(rel->r_info);
  203                 symidx = ELF_R_SYM(rel->r_info);
  204                 /* Addend is 32 bit on 32 bit relocs */
  205                 switch (rtype) {
  206                 case R_X86_64_PC32:
  207                 case R_X86_64_32S:
  208                 case R_X86_64_PLT32:
  209                         addend = *(Elf32_Addr *)where;
  210                         break;
  211                 default:
  212                         addend = *where;
  213                         break;
  214                 }
  215                 break;
  216         case ELF_RELOC_RELA:
  217                 rela = (const Elf_Rela *)data;
  218                 where = (Elf_Addr *) (relocbase + rela->r_offset);
  219                 addend = rela->r_addend;
  220                 rtype = ELF_R_TYPE(rela->r_info);
  221                 symidx = ELF_R_SYM(rela->r_info);
  222                 break;
  223         default:
  224                 panic("unknown reloc type %d\n", type);
  225         }
  226 
  227         switch (rtype) {
  228                 case R_X86_64_NONE:     /* none */
  229                         break;
  230 
  231                 case R_X86_64_64:               /* S + A */
  232                         error = lookup(lf, symidx, 1, &addr);
  233                         val = addr + addend;
  234                         if (error != 0)
  235                                 return -1;
  236                         if (*where != val)
  237                                 *where = val;
  238                         break;
  239 
  240                 case R_X86_64_PC32:     /* S + A - P */
  241                 case R_X86_64_PLT32:    /* L + A - P, L is PLT location for
  242                                            the symbol, which we treat as S */
  243                         error = lookup(lf, symidx, 1, &addr);
  244                         where32 = (Elf32_Addr *)where;
  245                         val32 = (Elf32_Addr)(addr + addend - (Elf_Addr)where);
  246                         if (error != 0)
  247                                 return -1;
  248                         if (*where32 != val32)
  249                                 *where32 = val32;
  250                         break;
  251 
  252                 case R_X86_64_32S:      /* S + A sign extend */
  253                         error = lookup(lf, symidx, 1, &addr);
  254                         val32 = (Elf32_Addr)(addr + addend);
  255                         where32 = (Elf32_Addr *)where;
  256                         if (error != 0)
  257                                 return -1;
  258                         if (*where32 != val32)
  259                                 *where32 = val32;
  260                         break;
  261 
  262                 case R_X86_64_COPY:     /* none */
  263                         /*
  264                          * There shouldn't be copy relocations in kernel
  265                          * objects.
  266                          */
  267                         printf("kldload: unexpected R_COPY relocation\n");
  268                         return (-1);
  269                         break;
  270 
  271                 case R_X86_64_GLOB_DAT: /* S */
  272                 case R_X86_64_JMP_SLOT: /* XXX need addend + offset */
  273                         error = lookup(lf, symidx, 1, &addr);
  274                         if (error != 0)
  275                                 return -1;
  276                         if (*where != addr)
  277                                 *where = addr;
  278                         break;
  279 
  280                 case R_X86_64_RELATIVE: /* B + A */
  281                         addr = relocbase + addend;
  282                         val = addr;
  283                         if (*where != val)
  284                                 *where = val;
  285                         break;
  286 
  287                 case R_X86_64_IRELATIVE:
  288                         addr = relocbase + addend;
  289                         val = ((Elf64_Addr (*)(void))addr)();
  290                         if (*where != val)
  291                                 *where = val;
  292                         break;
  293 
  294                 default:
  295                         printf("kldload: unexpected relocation type %ld\n",
  296                                rtype);
  297                         return (-1);
  298         }
  299         return (0);
  300 }
  301 
  302 int
  303 elf_reloc(linker_file_t lf, Elf_Addr relocbase, const void *data, int type,
  304     elf_lookup_fn lookup)
  305 {
  306 
  307         return (elf_reloc_internal(lf, relocbase, data, type, lookup));
  308 }
  309 
  310 int
  311 elf_reloc_local(linker_file_t lf, Elf_Addr relocbase, const void *data,
  312     int type, elf_lookup_fn lookup)
  313 {
  314 
  315         return (elf_reloc_internal(lf, relocbase, data, type, lookup));
  316 }
  317 
  318 int
  319 elf_cpu_load_file(linker_file_t lf __unused)
  320 {
  321 
  322         return (0);
  323 }
  324 
  325 int
  326 elf_cpu_unload_file(linker_file_t lf __unused)
  327 {
  328 
  329         return (0);
  330 }

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