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 #include <elf.h>
  49 #include <errno.h>
  50 #include <fcntl.h>
  51 #include <stdarg.h>
  52 #include <stdbool.h>
  53 #include <stdio.h>
  54 #include <stdlib.h>
  55 #include <string.h>
  56 #include <sys/mman.h>
  57 #include <sys/stat.h>
  58 #include <sys/types.h>
  59 #include <unistd.h>
  60
  61 #define swab16(x) \
  62         ((((x) & 0x00ff) << 8) | \
  63          (((x) & 0xff00) >> 8))
  64
  65 #define swab32(x) \
  66         ((((x) & 0x000000ff) << 24) | \
  67          (((x) & 0x0000ff00) <<  8) | \
  68          (((x) & 0x00ff0000) >>  8) | \
  69          (((x) & 0xff000000) >> 24))
  70
  71 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
  72 #define HOST_ORDER ELFDATA2LSB
  73 #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
  74 #define HOST_ORDER ELFDATA2MSB
  75 #endif
  76
  77 /* Some of the ELF constants we'd like to use were added to <elf.h>
  78  * relatively recently.
  79  */
  80 #ifndef EF_ARM_EABI_VER5
  81 #define EF_ARM_EABI_VER5 0x05000000
  82 #endif
  83
  84 #ifndef EF_ARM_ABI_FLOAT_SOFT
  85 #define EF_ARM_ABI_FLOAT_SOFT 0x200
  86 #endif
  87
  88 #ifndef EF_ARM_ABI_FLOAT_HARD
  89 #define EF_ARM_ABI_FLOAT_HARD 0x400
  90 #endif
  91
  92 static int failed;
  93 static const char *argv0;
  94 static const char *outfile;
  95
  96 static void fail(const char *fmt, ...)
  97 {
  98         va_list ap;
  99
 100         failed = 1;
 101         fprintf(stderr, "%s: ", argv0);
 102         va_start(ap, fmt);
 103         vfprintf(stderr, fmt, ap);
 104         va_end(ap);
 105         exit(EXIT_FAILURE);
 106 }
 107
 108 static void cleanup(void)
 109 {
 110         if (failed && outfile != NULL)
 111                 unlink(outfile);
 112 }
 113
 114 static Elf32_Word read_elf_word(Elf32_Word word, bool swap)
 115 {
 116         return swap ? swab32(word) : word;
 117 }
 118
 119 static Elf32_Half read_elf_half(Elf32_Half half, bool swap)
 120 {
 121         return swap ? swab16(half) : half;
 122 }
 123
 124 static void write_elf_word(Elf32_Word val, Elf32_Word *dst, bool swap)
 125 {
 126         *dst = swap ? swab32(val) : val;
 127 }
 128
 129 int main(int argc, char **argv)
 130 {
 131         const Elf32_Ehdr *inhdr;
 132         bool clear_soft_float;
 133         const char *infile;
 134         Elf32_Word e_flags;
 135         const void *inbuf;
 136         struct stat stat;
 137         void *outbuf;
 138         bool swap;
 139         int outfd;
 140         int infd;
 141
 142         atexit(cleanup);
 143         argv0 = argv[0];
 144
 145         if (argc != 3)
 146                 fail("Usage: %s [infile] [outfile]\n", argv[0]);
 147
 148         infile = argv[1];
 149         outfile = argv[2];
 150
 151         infd = open(infile, O_RDONLY);
 152         if (infd < 0)
 153                 fail("Cannot open %s: %s\n", infile, strerror(errno));
 154
 155         if (fstat(infd, &stat) != 0)
 156                 fail("Failed stat for %s: %s\n", infile, strerror(errno));
 157
 158         inbuf = mmap(NULL, stat.st_size, PROT_READ, MAP_PRIVATE, infd, 0);
 159         if (inbuf == MAP_FAILED)
 160                 fail("Failed to map %s: %s\n", infile, strerror(errno));
 161
 162         close(infd);
 163
 164         inhdr = inbuf;
 165
 166         if (memcmp(&inhdr->e_ident, ELFMAG, SELFMAG) != 0)
 167                 fail("Not an ELF file\n");
 168
 169         if (inhdr->e_ident[EI_CLASS] != ELFCLASS32)
 170                 fail("Unsupported ELF class\n");
 171
 172         swap = inhdr->e_ident[EI_DATA] != HOST_ORDER;
 173
 174         if (read_elf_half(inhdr->e_type, swap) != ET_DYN)
 175                 fail("Not a shared object\n");
 176
 177         if (read_elf_half(inhdr->e_machine, swap) != EM_ARM)
 178                 fail("Unsupported architecture %#x\n", inhdr->e_machine);
 179
 180         e_flags = read_elf_word(inhdr->e_flags, swap);
 181
 182         if (EF_ARM_EABI_VERSION(e_flags) != EF_ARM_EABI_VER5) {
 183                 fail("Unsupported EABI version %#x\n",
 184                      EF_ARM_EABI_VERSION(e_flags));
 185         }
 186
 187         if (e_flags & EF_ARM_ABI_FLOAT_HARD)
 188                 fail("Unexpected hard-float flag set in e_flags\n");
 189
 190         clear_soft_float = !!(e_flags & EF_ARM_ABI_FLOAT_SOFT);
 191
 192         outfd = open(outfile, O_RDWR | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
 193         if (outfd < 0)
 194                 fail("Cannot open %s: %s\n", outfile, strerror(errno));
 195
 196         if (ftruncate(outfd, stat.st_size) != 0)
 197                 fail("Cannot truncate %s: %s\n", outfile, strerror(errno));
 198
 199         outbuf = mmap(NULL, stat.st_size, PROT_READ | PROT_WRITE, MAP_SHARED,
 200                       outfd, 0);
 201         if (outbuf == MAP_FAILED)
 202                 fail("Failed to map %s: %s\n", outfile, strerror(errno));
 203
 204         close(outfd);
 205
 206         memcpy(outbuf, inbuf, stat.st_size);
 207
 208         if (clear_soft_float) {
 209                 Elf32_Ehdr *outhdr;
 210
 211                 outhdr = outbuf;
 212                 e_flags &= ~EF_ARM_ABI_FLOAT_SOFT;
 213                 write_elf_word(e_flags, &outhdr->e_flags, swap);
 214         }
 215
 216         if (msync(outbuf, stat.st_size, MS_SYNC) != 0)
 217                 fail("Failed to sync %s: %s\n", outfile, strerror(errno));
 218
 219         return EXIT_SUCCESS;
 220 }