arch/arm/vdso/vdsomunge.c

   1 /*
   2  * Copyright 2015 Mentor Graphics Corporation.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; version 2 of the
   7  * License.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16  *
  17  *
  18  * vdsomunge - Host program which produces a shared object
  19  * architecturally specified to be usable by both soft- and hard-float
  20  * programs.
  21  *
  22  * The Procedure Call Standard for the ARM Architecture (ARM IHI
  23  * 0042E) says:
  24  *
  25  *      6.4.1 VFP and Base Standard Compatibility
  26  *
  27  *      Code compiled for the VFP calling standard is compatible with
  28  *      the base standard (and vice-versa) if no floating-point or
  29  *      containerized vector arguments or results are used.
  30  *
  31  * And ELF for the ARM Architecture (ARM IHI 0044E) (Table 4-2) says:
  32  *
  33  *      If both EF_ARM_ABI_FLOAT_XXXX bits are clear, conformance to the
  34  *      base procedure-call standard is implied.
  35  *
  36  * The VDSO is built with -msoft-float, as with the rest of the ARM
  37  * kernel, and uses no floating point arguments or results.  The build
  38  * process will produce a shared object that may or may not have the
  39  * EF_ARM_ABI_FLOAT_SOFT flag set (it seems to depend on the binutils
  40  * version; binutils starting with 2.24 appears to set it).  The
  41  * EF_ARM_ABI_FLOAT_HARD flag should definitely not be set, and this
  42  * program will error out if it is.
  43  *
  44  * If the soft-float flag is set, this program clears it.  That's all
  45  * it does.
  46  */
  47
  48 #define _GNU_SOURCE
  49
  50 #include <byteswap.h>
  51 #include <elf.h>
  52 #include <errno.h>
  53 #include <error.h>
  54 #include <fcntl.h>
  55 #include <stdbool.h>
  56 #include <stdio.h>
  57 #include <stdlib.h>
  58 #include <string.h>
  59 #include <sys/mman.h>
  60 #include <sys/stat.h>
  61 #include <sys/types.h>
  62 #include <unistd.h>
  63
  64 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
  65 #define HOST_ORDER ELFDATA2LSB
  66 #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
  67 #define HOST_ORDER ELFDATA2MSB
  68 #endif
  69
  70 /* Some of the ELF constants we'd like to use were added to <elf.h>
  71  * relatively recently.
  72  */
  73 #ifndef EF_ARM_EABI_VER5
  74 #define EF_ARM_EABI_VER5 0x05000000
  75 #endif
  76
  77 #ifndef EF_ARM_ABI_FLOAT_SOFT
  78 #define EF_ARM_ABI_FLOAT_SOFT 0x200
  79 #endif
  80
  81 #ifndef EF_ARM_ABI_FLOAT_HARD
  82 #define EF_ARM_ABI_FLOAT_HARD 0x400
  83 #endif
  84
  85 static const char *outfile;
  86
  87 static void cleanup(void)
  88 {
  89         if (error_message_count > 0 && outfile != NULL)
  90                 unlink(outfile);
  91 }
  92
  93 static Elf32_Word read_elf_word(Elf32_Word word, bool swap)
  94 {
  95         return swap ? bswap_32(word) : word;
  96 }
  97
  98 static Elf32_Half read_elf_half(Elf32_Half half, bool swap)
  99 {
 100         return swap ? bswap_16(half) : half;
 101 }
 102
 103 static void write_elf_word(Elf32_Word val, Elf32_Word *dst, bool swap)
 104 {
 105         *dst = swap ? bswap_32(val) : val;
 106 }
 107
 108 int main(int argc, char **argv)
 109 {
 110         const Elf32_Ehdr *inhdr;
 111         bool clear_soft_float;
 112         const char *infile;
 113         Elf32_Word e_flags;
 114         const void *inbuf;
 115         struct stat stat;
 116         void *outbuf;
 117         bool swap;
 118         int outfd;
 119         int infd;
 120
 121         atexit(cleanup);
 122
 123         if (argc != 3)
 124                 error(EXIT_FAILURE, 0, "Usage: %s [infile] [outfile]", argv[0]);
 125
 126         infile = argv[1];
 127         outfile = argv[2];
 128
 129         infd = open(infile, O_RDONLY);
 130         if (infd < 0)
 131                 error(EXIT_FAILURE, errno, "Cannot open %s", infile);
 132
 133         if (fstat(infd, &stat) != 0)
 134                 error(EXIT_FAILURE, errno, "Failed stat for %s", infile);
 135
 136         inbuf = mmap(NULL, stat.st_size, PROT_READ, MAP_PRIVATE, infd, 0);
 137         if (inbuf == MAP_FAILED)
 138                 error(EXIT_FAILURE, errno, "Failed to map %s", infile);
 139
 140         close(infd);
 141
 142         inhdr = inbuf;
 143
 144         if (memcmp(&inhdr->e_ident, ELFMAG, SELFMAG) != 0)
 145                 error(EXIT_FAILURE, 0, "Not an ELF file");
 146
 147         if (inhdr->e_ident[EI_CLASS] != ELFCLASS32)
 148                 error(EXIT_FAILURE, 0, "Unsupported ELF class");
 149
 150         swap = inhdr->e_ident[EI_DATA] != HOST_ORDER;
 151
 152         if (read_elf_half(inhdr->e_type, swap) != ET_DYN)
 153                 error(EXIT_FAILURE, 0, "Not a shared object");
 154
 155         if (read_elf_half(inhdr->e_machine, swap) != EM_ARM) {
 156                 error(EXIT_FAILURE, 0, "Unsupported architecture %#x",
 157                       inhdr->e_machine);
 158         }
 159
 160         e_flags = read_elf_word(inhdr->e_flags, swap);
 161
 162         if (EF_ARM_EABI_VERSION(e_flags) != EF_ARM_EABI_VER5) {
 163                 error(EXIT_FAILURE, 0, "Unsupported EABI version %#x",
 164                       EF_ARM_EABI_VERSION(e_flags));
 165         }
 166
 167         if (e_flags & EF_ARM_ABI_FLOAT_HARD)
 168                 error(EXIT_FAILURE, 0,
 169                       "Unexpected hard-float flag set in e_flags");
 170
 171         clear_soft_float = !!(e_flags & EF_ARM_ABI_FLOAT_SOFT);
 172
 173         outfd = open(outfile, O_RDWR | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
 174         if (outfd < 0)
 175                 error(EXIT_FAILURE, errno, "Cannot open %s", outfile);
 176
 177         if (ftruncate(outfd, stat.st_size) != 0)
 178                 error(EXIT_FAILURE, errno, "Cannot truncate %s", outfile);
 179
 180         outbuf = mmap(NULL, stat.st_size, PROT_READ | PROT_WRITE, MAP_SHARED,
 181                       outfd, 0);
 182         if (outbuf == MAP_FAILED)
 183                 error(EXIT_FAILURE, errno, "Failed to map %s", outfile);
 184
 185         close(outfd);
 186
 187         memcpy(outbuf, inbuf, stat.st_size);
 188
 189         if (clear_soft_float) {
 190                 Elf32_Ehdr *outhdr;
 191
 192                 outhdr = outbuf;
 193                 e_flags &= ~EF_ARM_ABI_FLOAT_SOFT;
 194                 write_elf_word(e_flags, &outhdr->e_flags, swap);
 195         }
 196
 197         if (msync(outbuf, stat.st_size, MS_SYNC) != 0)
 198                 error(EXIT_FAILURE, errno, "Failed to sync %s", outfile);
 199
 200         return EXIT_SUCCESS;
 201 }