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 };
  67
  68 struct vdso_sym {
  69         const char *name;
  70         int export;
  71 };
  72
  73 struct vdso_sym required_syms[] = {
  74         [sym_vvar_start] = {"vvar_start", 1},
  75         [sym_VDSO_FAKE_SECTION_TABLE_START] = {
  76                 "VDSO_FAKE_SECTION_TABLE_START", 0
  77         },
  78         [sym_VDSO_FAKE_SECTION_TABLE_END] = {
  79                 "VDSO_FAKE_SECTION_TABLE_END", 0
  80         },
  81 };
  82
  83 __attribute__((format(printf, 1, 2))) __attribute__((noreturn))
  84 static void fail(const char *format, ...)
  85 {
  86         va_list ap;
  87
  88         va_start(ap, format);
  89         fprintf(stderr, "Error: ");
  90         vfprintf(stderr, format, ap);
  91         if (outfilename)
  92                 unlink(outfilename);
  93         exit(1);
  94         va_end(ap);
  95 }
  96
  97 /*
  98  * Evil macros for big-endian reads and writes
  99  */
 100 #define GBE(x, bits, ifnot)                                             \
 101         __builtin_choose_expr(                                          \
 102                 (sizeof(*(x)) == bits/8),                               \
 103                 (__typeof__(*(x)))get_unaligned_be##bits(x), ifnot)
 104
 105 #define LAST_GBE(x)                                                     \
 106         __builtin_choose_expr(sizeof(*(x)) == 1, *(x), (void)(0))
 107
 108 #define GET_BE(x)                                                       \
 109         GBE(x, 64, GBE(x, 32, GBE(x, 16, LAST_GBE(x))))
 110
 111 #define PBE(x, val, bits, ifnot)                                        \
 112         __builtin_choose_expr(                                          \
 113                 (sizeof(*(x)) == bits/8),                               \
 114                 put_unaligned_be##bits((val), (x)), ifnot)
 115
 116 #define LAST_PBE(x, val)                                                \
 117         __builtin_choose_expr(sizeof(*(x)) == 1, *(x) = (val), (void)(0))
 118
 119 #define PUT_BE(x, val)                                  \
 120         PBE(x, val, 64, PBE(x, val, 32, PBE(x, val, 16, LAST_PBE(x, val))))
 121
 122 #define NSYMS ARRAY_SIZE(required_syms)
 123
 124 #define BITSFUNC3(name, bits, suffix) name##bits##suffix
 125 #define BITSFUNC2(name, bits, suffix) BITSFUNC3(name, bits, suffix)
 126 #define BITSFUNC(name) BITSFUNC2(name, ELF_BITS, )
 127
 128 #define INT_BITS BITSFUNC2(int, ELF_BITS, _t)
 129
 130 #define ELF_BITS_XFORM2(bits, x) Elf##bits##_##x
 131 #define ELF_BITS_XFORM(bits, x) ELF_BITS_XFORM2(bits, x)
 132 #define ELF(x) ELF_BITS_XFORM(ELF_BITS, x)
 133
 134 #define ELF_BITS 64
 135 #include "vdso2c.h"
 136 #undef ELF_BITS
 137
 138 #define ELF_BITS 32
 139 #include "vdso2c.h"
 140 #undef ELF_BITS
 141
 142 static void go(void *raw_addr, size_t raw_len,
 143                void *stripped_addr, size_t stripped_len,
 144                FILE *outfile, const char *name)
 145 {
 146         Elf64_Ehdr *hdr = (Elf64_Ehdr *)raw_addr;
 147
 148         if (hdr->e_ident[EI_CLASS] == ELFCLASS64) {
 149                 go64(raw_addr, raw_len, stripped_addr, stripped_len,
 150                      outfile, name);
 151         } else if (hdr->e_ident[EI_CLASS] == ELFCLASS32) {
 152                 go32(raw_addr, raw_len, stripped_addr, stripped_len,
 153                      outfile, name);
 154         } else {
 155                 fail("unknown ELF class\n");
 156         }
 157 }
 158
 159 static void map_input(const char *name, void **addr, size_t *len, int prot)
 160 {
 161         off_t tmp_len;
 162
 163         int fd = open(name, O_RDONLY);
 164
 165         if (fd == -1)
 166                 err(1, "%s", name);
 167
 168         tmp_len = lseek(fd, 0, SEEK_END);
 169         if (tmp_len == (off_t)-1)
 170                 err(1, "lseek");
 171         *len = (size_t)tmp_len;
 172
 173         *addr = mmap(NULL, tmp_len, prot, MAP_PRIVATE, fd, 0);
 174         if (*addr == MAP_FAILED)
 175                 err(1, "mmap");
 176
 177         close(fd);
 178 }
 179
 180 int main(int argc, char **argv)
 181 {
 182         size_t raw_len, stripped_len;
 183         void *raw_addr, *stripped_addr;
 184         FILE *outfile;
 185         char *name, *tmp;
 186         int namelen;
 187
 188         if (argc != 4) {
 189                 printf("Usage: vdso2c RAW_INPUT STRIPPED_INPUT OUTPUT\n");
 190                 return 1;
 191         }
 192
 193         /*
 194          * Figure out the struct name.  If we're writing to a .so file,
 195          * generate raw output insted.
 196          */
 197         name = strdup(argv[3]);
 198         namelen = strlen(name);
 199         if (namelen >= 3 && !strcmp(name + namelen - 3, ".so")) {
 200                 name = NULL;
 201         } else {
 202                 tmp = strrchr(name, '/');
 203                 if (tmp)
 204                         name = tmp + 1;
 205                 tmp = strchr(name, '.');
 206                 if (tmp)
 207                         *tmp = '\0';
 208                 for (tmp = name; *tmp; tmp++)
 209                         if (*tmp == '-')
 210                                 *tmp = '_';
 211         }
 212
 213         map_input(argv[1], &raw_addr, &raw_len, PROT_READ);
 214         map_input(argv[2], &stripped_addr, &stripped_len, PROT_READ);
 215
 216         outfilename = argv[3];
 217         outfile = fopen(outfilename, "w");
 218         if (!outfile)
 219                 err(1, "%s", argv[2]);
 220
 221         go(raw_addr, raw_len, stripped_addr, stripped_len, outfile, name);
 222
 223         munmap(raw_addr, raw_len);
 224         munmap(stripped_addr, stripped_len);
 225         fclose(outfile);
 226
 227         return 0;
 228 }