root/arch/arm/vdso/vdsomunge.c

DEFINITIONS

1. fail
2. cleanup
3. read_elf_word
4. read_elf_half
5. write_elf_word
6. main

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright 2015 Mentor Graphics Corporation.
   4  *
   5  * vdsomunge - Host program which produces a shared object
   6  * architecturally specified to be usable by both soft- and hard-float
   7  * programs.
   8  *
   9  * The Procedure Call Standard for the ARM Architecture (ARM IHI
  10  * 0042E) says:
  11  *
  12  *      6.4.1 VFP and Base Standard Compatibility
  13  *
  14  *      Code compiled for the VFP calling standard is compatible with
  15  *      the base standard (and vice-versa) if no floating-point or
  16  *      containerized vector arguments or results are used.
  17  *
  18  * And ELF for the ARM Architecture (ARM IHI 0044E) (Table 4-2) says:
  19  *
  20  *      If both EF_ARM_ABI_FLOAT_XXXX bits are clear, conformance to the
  21  *      base procedure-call standard is implied.
  22  *
  23  * The VDSO is built with -msoft-float, as with the rest of the ARM
  24  * kernel, and uses no floating point arguments or results.  The build
  25  * process will produce a shared object that may or may not have the
  26  * EF_ARM_ABI_FLOAT_SOFT flag set (it seems to depend on the binutils
  27  * version; binutils starting with 2.24 appears to set it).  The
  28  * EF_ARM_ABI_FLOAT_HARD flag should definitely not be set, and this
  29  * program will error out if it is.
  30  *
  31  * If the soft-float flag is set, this program clears it.  That's all
  32  * it does.
  33  */
  34 
  35 #include <elf.h>
  36 #include <errno.h>
  37 #include <fcntl.h>
  38 #include <stdarg.h>
  39 #include <stdbool.h>
  40 #include <stdio.h>
  41 #include <stdlib.h>
  42 #include <string.h>
  43 #include <sys/mman.h>
  44 #include <sys/stat.h>
  45 #include <sys/types.h>
  46 #include <unistd.h>
  47 
  48 #define swab16(x) \
  49         ((((x) & 0x00ff) << 8) | \
  50          (((x) & 0xff00) >> 8))
  51 
  52 #define swab32(x) \
  53         ((((x) & 0x000000ff) << 24) | \
  54          (((x) & 0x0000ff00) <<  8) | \
  55          (((x) & 0x00ff0000) >>  8) | \
  56          (((x) & 0xff000000) >> 24))
  57 
  58 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
  59 #define HOST_ORDER ELFDATA2LSB
  60 #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
  61 #define HOST_ORDER ELFDATA2MSB
  62 #endif
  63 
  64 /* Some of the ELF constants we'd like to use were added to <elf.h>
  65  * relatively recently.
  66  */
  67 #ifndef EF_ARM_EABI_VER5
  68 #define EF_ARM_EABI_VER5 0x05000000
  69 #endif
  70 
  71 #ifndef EF_ARM_ABI_FLOAT_SOFT
  72 #define EF_ARM_ABI_FLOAT_SOFT 0x200
  73 #endif
  74 
  75 #ifndef EF_ARM_ABI_FLOAT_HARD
  76 #define EF_ARM_ABI_FLOAT_HARD 0x400
  77 #endif
  78 
  79 static int failed;
  80 static const char *argv0;
  81 static const char *outfile;
  82 
  83 static void fail(const char *fmt, ...)
  84 {
  85         va_list ap;
  86 
  87         failed = 1;
  88         fprintf(stderr, "%s: ", argv0);
  89         va_start(ap, fmt);
  90         vfprintf(stderr, fmt, ap);
  91         va_end(ap);
  92         exit(EXIT_FAILURE);
  93 }
  94 
  95 static void cleanup(void)
  96 {
  97         if (failed && outfile != NULL)
  98                 unlink(outfile);
  99 }
 100 
 101 static Elf32_Word read_elf_word(Elf32_Word word, bool swap)
 102 {
 103         return swap ? swab32(word) : word;
 104 }
 105 
 106 static Elf32_Half read_elf_half(Elf32_Half half, bool swap)
 107 {
 108         return swap ? swab16(half) : half;
 109 }
 110 
 111 static void write_elf_word(Elf32_Word val, Elf32_Word *dst, bool swap)
 112 {
 113         *dst = swap ? swab32(val) : val;
 114 }
 115 
 116 int main(int argc, char **argv)
 117 {
 118         const Elf32_Ehdr *inhdr;
 119         bool clear_soft_float;
 120         const char *infile;
 121         Elf32_Word e_flags;
 122         const void *inbuf;
 123         struct stat stat;
 124         void *outbuf;
 125         bool swap;
 126         int outfd;
 127         int infd;
 128 
 129         atexit(cleanup);
 130         argv0 = argv[0];
 131 
 132         if (argc != 3)
 133                 fail("Usage: %s [infile] [outfile]\n", argv[0]);
 134 
 135         infile = argv[1];
 136         outfile = argv[2];
 137 
 138         infd = open(infile, O_RDONLY);
 139         if (infd < 0)
 140                 fail("Cannot open %s: %s\n", infile, strerror(errno));
 141 
 142         if (fstat(infd, &stat) != 0)
 143                 fail("Failed stat for %s: %s\n", infile, strerror(errno));
 144 
 145         inbuf = mmap(NULL, stat.st_size, PROT_READ, MAP_PRIVATE, infd, 0);
 146         if (inbuf == MAP_FAILED)
 147                 fail("Failed to map %s: %s\n", infile, strerror(errno));
 148 
 149         close(infd);
 150 
 151         inhdr = inbuf;
 152 
 153         if (memcmp(&inhdr->e_ident, ELFMAG, SELFMAG) != 0)
 154                 fail("Not an ELF file\n");
 155 
 156         if (inhdr->e_ident[EI_CLASS] != ELFCLASS32)
 157                 fail("Unsupported ELF class\n");
 158 
 159         swap = inhdr->e_ident[EI_DATA] != HOST_ORDER;
 160 
 161         if (read_elf_half(inhdr->e_type, swap) != ET_DYN)
 162                 fail("Not a shared object\n");
 163 
 164         if (read_elf_half(inhdr->e_machine, swap) != EM_ARM)
 165                 fail("Unsupported architecture %#x\n", inhdr->e_machine);
 166 
 167         e_flags = read_elf_word(inhdr->e_flags, swap);
 168 
 169         if (EF_ARM_EABI_VERSION(e_flags) != EF_ARM_EABI_VER5) {
 170                 fail("Unsupported EABI version %#x\n",
 171                      EF_ARM_EABI_VERSION(e_flags));
 172         }
 173 
 174         if (e_flags & EF_ARM_ABI_FLOAT_HARD)
 175                 fail("Unexpected hard-float flag set in e_flags\n");
 176 
 177         clear_soft_float = !!(e_flags & EF_ARM_ABI_FLOAT_SOFT);
 178 
 179         outfd = open(outfile, O_RDWR | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
 180         if (outfd < 0)
 181                 fail("Cannot open %s: %s\n", outfile, strerror(errno));
 182 
 183         if (ftruncate(outfd, stat.st_size) != 0)
 184                 fail("Cannot truncate %s: %s\n", outfile, strerror(errno));
 185 
 186         outbuf = mmap(NULL, stat.st_size, PROT_READ | PROT_WRITE, MAP_SHARED,
 187                       outfd, 0);
 188         if (outbuf == MAP_FAILED)
 189                 fail("Failed to map %s: %s\n", outfile, strerror(errno));
 190 
 191         close(outfd);
 192 
 193         memcpy(outbuf, inbuf, stat.st_size);
 194 
 195         if (clear_soft_float) {
 196                 Elf32_Ehdr *outhdr;
 197 
 198                 outhdr = outbuf;
 199                 e_flags &= ~EF_ARM_ABI_FLOAT_SOFT;
 200                 write_elf_word(e_flags, &outhdr->e_flags, swap);
 201         }
 202 
 203         if (msync(outbuf, stat.st_size, MS_SYNC) != 0)
 204                 fail("Failed to sync %s: %s\n", outfile, strerror(errno));
 205 
 206         return EXIT_SUCCESS;
 207 }