arch/sparc/vdso/vdso2c.c

   1 /*
   2  * vdso2c - A vdso image preparation tool
   3  * Copyright (c) 2014 Andy Lutomirski and others
   4  * Licensed under the GPL v2
   5  *
   6  * vdso2c requires stripped and unstripped input.  It would be trivial
   7  * to fully strip the input in here, but, for reasons described below,
   8  * we need to write a section table.  Doing this is more or less
   9  * equivalent to dropping all non-allocatable sections, but it's
  10  * easier to let objcopy handle that instead of doing it ourselves.
  11  * If we ever need to do something fancier than what objcopy provides,
  12  * it would be straightforward to add here.
  13  *
  14  * We keep a section table for a few reasons:
  15  *
  16  * Binutils has issues debugging the vDSO: it reads the section table to
  17  * find SHT_NOTE; it won't look at PT_NOTE for the in-memory vDSO, which
  18  * would break build-id if we removed the section table.  Binutils
  19  * also requires that shstrndx != 0.  See:
  20  * https://sourceware.org/bugzilla/show_bug.cgi?id=17064
  21  *
  22  * elfutils might not look for PT_NOTE if there is a section table at
  23  * all.  I don't know whether this matters for any practical purpose.
  24  *
  25  * For simplicity, rather than hacking up a partial section table, we
  26  * just write a mostly complete one.  We omit non-dynamic symbols,
  27  * though, since they're rather large.
  28  *
  29  * Once binutils gets fixed, we might be able to drop this for all but
  30  * the 64-bit vdso, since build-id only works in kernel RPMs, and
  31  * systems that update to new enough kernel RPMs will likely update
  32  * binutils in sync.  build-id has never worked for home-built kernel
  33  * RPMs without manual symlinking, and I suspect that no one ever does
  34  * that.
  35  */
  36
  37 /*
  38  * Copyright (c) 2017 Oracle and/or its affiliates. All rights reserved.
  39  */
  40
  41 #include <inttypes.h>
  42 #include <stdint.h>
  43 #include <unistd.h>
  44 #include <stdarg.h>
  45 #include <stdlib.h>
  46 #include <stdio.h>
  47 #include <string.h>
  48 #include <fcntl.h>
  49 #include <err.h>
  50
  51 #include <sys/mman.h>
  52 #include <sys/types.h>
  53 #include <tools/be_byteshift.h>
  54
  55 #include <linux/elf.h>
  56 #include <linux/types.h>
  57 #include <linux/kernel.h>
  58
  59 const char *outfilename;
  60
  61 /* Symbols that we need in vdso2c. */
  62 enum {
  63         sym_vvar_start,
  64         sym_VDSO_FAKE_SECTION_TABLE_START,
  65         sym_VDSO_FAKE_SECTION_TABLE_END,
  66         sym_vread_tick,
  67         sym_vread_tick_patch_start,
  68         sym_vread_tick_patch_end
  69 };
  70
  71 struct vdso_sym {
  72         const char *name;
  73         int export;
  74 };
  75
  76 struct vdso_sym required_syms[] = {
  77         [sym_vvar_start] = {"vvar_start", 1},
  78         [sym_VDSO_FAKE_SECTION_TABLE_START] = {
  79                 "VDSO_FAKE_SECTION_TABLE_START", 0
  80         },
  81         [sym_VDSO_FAKE_SECTION_TABLE_END] = {
  82                 "VDSO_FAKE_SECTION_TABLE_END", 0
  83         },
  84         [sym_vread_tick] = {"vread_tick", 1},
  85         [sym_vread_tick_patch_start] = {"vread_tick_patch_start", 1},
  86         [sym_vread_tick_patch_end] = {"vread_tick_patch_end", 1}
  87 };
  88
  89 __attribute__((format(printf, 1, 2))) __attribute__((noreturn))
  90 static void fail(const char *format, ...)
  91 {
  92         va_list ap;
  93
  94         va_start(ap, format);
  95         fprintf(stderr, "Error: ");
  96         vfprintf(stderr, format, ap);
  97         if (outfilename)
  98                 unlink(outfilename);
  99         exit(1);
 100         va_end(ap);
 101 }
 102
 103 /*
 104  * Evil macros for big-endian reads and writes
 105  */
 106 #define GBE(x, bits, ifnot)                                             \
 107         __builtin_choose_expr(                                          \
 108                 (sizeof(*(x)) == bits/8),                               \
 109                 (__typeof__(*(x)))get_unaligned_be##bits(x), ifnot)
 110
 111 #define LAST_GBE(x)                                                     \
 112         __builtin_choose_expr(sizeof(*(x)) == 1, *(x), (void)(0))
 113
 114 #define GET_BE(x)                                                       \
 115         GBE(x, 64, GBE(x, 32, GBE(x, 16, LAST_GBE(x))))
 116
 117 #define PBE(x, val, bits, ifnot)                                        \
 118         __builtin_choose_expr(                                          \
 119                 (sizeof(*(x)) == bits/8),                               \
 120                 put_unaligned_be##bits((val), (x)), ifnot)
 121
 122 #define LAST_PBE(x, val)                                                \
 123         __builtin_choose_expr(sizeof(*(x)) == 1, *(x) = (val), (void)(0))
 124
 125 #define PUT_BE(x, val)                                  \
 126         PBE(x, val, 64, PBE(x, val, 32, PBE(x, val, 16, LAST_PBE(x, val))))
 127
 128 #define NSYMS ARRAY_SIZE(required_syms)
 129
 130 #define BITSFUNC3(name, bits, suffix) name##bits##suffix
 131 #define BITSFUNC2(name, bits, suffix) BITSFUNC3(name, bits, suffix)
 132 #define BITSFUNC(name) BITSFUNC2(name, ELF_BITS, )
 133
 134 #define INT_BITS BITSFUNC2(int, ELF_BITS, _t)
 135
 136 #define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x
 137 #define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
 138 #define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
 139
 140 #define ELF_BITS 64
 141 #include "vdso2c.h"
 142 #undef ELF_BITS
 143
 144 #define ELF_BITS 32
 145 #include "vdso2c.h"
 146 #undef ELF_BITS
 147
 148 static void go(void *raw_addr, size_t raw_len,
 149                void *stripped_addr, size_t stripped_len,
 150                FILE *outfile, const char *name)
 151 {
 152         Elf64_Ehdr *hdr = (Elf64_Ehdr *)raw_addr;
 153
 154         if (hdr->e_ident[EI_CLASS] == ELFCLASS64) {
 155                 go64(raw_addr, raw_len, stripped_addr, stripped_len,
 156                      outfile, name);
 157         } else if (hdr->e_ident[EI_CLASS] == ELFCLASS32) {
 158                 go32(raw_addr, raw_len, stripped_addr, stripped_len,
 159                      outfile, name);
 160         } else {
 161                 fail("unknown ELF class\n");
 162         }
 163 }
 164
 165 static void map_input(const char *name, void **addr, size_t *len, int prot)
 166 {
 167         off_t tmp_len;
 168
 169         int fd = open(name, O_RDONLY);
 170
 171         if (fd == -1)
 172                 err(1, "%s", name);
 173
 174         tmp_len = lseek(fd, 0, SEEK_END);
 175         if (tmp_len == (off_t)-1)
 176                 err(1, "lseek");
 177         *len = (size_t)tmp_len;
 178
 179         *addr = mmap(NULL, tmp_len, prot, MAP_PRIVATE, fd, 0);
 180         if (*addr == MAP_FAILED)
 181                 err(1, "mmap");
 182
 183         close(fd);
 184 }
 185
 186 int main(int argc, char **argv)
 187 {
 188         size_t raw_len, stripped_len;
 189         void *raw_addr, *stripped_addr;
 190         FILE *outfile;
 191         char *name, *tmp;
 192         int namelen;
 193
 194         if (argc != 4) {
 195                 printf("Usage: vdso2c RAW_INPUT STRIPPED_INPUT OUTPUT\n");
 196                 return 1;
 197         }
 198
 199         /*
 200          * Figure out the struct name.  If we're writing to a .so file,
 201          * generate raw output insted.
 202          */
 203         name = strdup(argv[3]);
 204         namelen = strlen(name);
 205         if (namelen >= 3 && !strcmp(name + namelen - 3, ".so")) {
 206                 name = NULL;
 207         } else {
 208                 tmp = strrchr(name, '/');
 209                 if (tmp)
 210                         name = tmp + 1;
 211                 tmp = strchr(name, '.');
 212                 if (tmp)
 213                         *tmp = '\0';
 214                 for (tmp = name; *tmp; tmp++)
 215                         if (*tmp == '-')
 216                                 *tmp = '_';
 217         }
 218
 219         map_input(argv[1], &raw_addr, &raw_len, PROT_READ);
 220         map_input(argv[2], &stripped_addr, &stripped_len, PROT_READ);
 221
 222         outfilename = argv[3];
 223         outfile = fopen(outfilename, "w");
 224         if (!outfile)
 225                 err(1, "%s", argv[2]);
 226
 227         go(raw_addr, raw_len, stripped_addr, stripped_len, outfile, name);
 228
 229         munmap(raw_addr, raw_len);
 230         munmap(stripped_addr, stripped_len);
 231         fclose(outfile);
 232
 233         return 0;
 234 }