gdb/testsuite/gdb.base/jit-elf-util.h

   1 /* This test program is part of GDB, the GNU debugger.
   2
   3    Copyright 2020-2023 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* Simulates loading of JIT code by memory mapping a compiled
  19    shared library binary and doing minimal post-processing.  */
  20
  21 #include <elf.h>
  22 #include <errno.h>
  23 #include <fcntl.h>
  24 #include <link.h>
  25 #include <stdint.h>
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <sys/mman.h>
  30 #include <sys/stat.h>
  31 #include <unistd.h>
  32
  33 /* ElfW is coming from linux. On other platforms it does not exist.
  34    Let us define it here. */
  35 #ifndef ElfW
  36 #if (defined(_LP64) || defined(__LP64__))
  37 #define WORDSIZE 64
  38 #else
  39 #define WORDSIZE 32
  40 #endif /* _LP64 || __LP64__  */
  41 #define ElfW(type) _ElfW (Elf, WORDSIZE, type)
  42 #define _ElfW(e, w, t) _ElfW_1 (e, w, _##t)
  43 #define _ElfW_1(e, w, t) e##w##t
  44 #endif /* !ElfW  */
  45
  46 /* Find symbol with the name `sym_name`.  */
  47 static void *
  48 load_symbol (void *addr, const char *sym_name)
  49 {
  50   const ElfW (Ehdr) *const ehdr = (ElfW (Ehdr) *) addr;
  51   ElfW (Shdr) *const shdr = (ElfW (Shdr) *) ((char *) addr + ehdr->e_shoff);
  52
  53   ElfW (Addr) sym_old_addr = 0;
  54   ElfW (Addr) sym_new_addr = 0;
  55
  56   /* Find `func_name` in symbol_table and return its address.  */
  57   int i;
  58   for (i = 0; i < ehdr->e_shnum; ++i)
  59     {
  60       if (shdr[i].sh_type == SHT_SYMTAB)
  61         {
  62           ElfW (Sym) *symtab = (ElfW (Sym) *) (addr + shdr[i].sh_offset);
  63           ElfW (Sym) *symtab_end
  64               = (ElfW (Sym) *) (addr + shdr[i].sh_offset + shdr[i].sh_size);
  65           char *const strtab
  66               = (char *) (addr + shdr[shdr[i].sh_link].sh_offset);
  67
  68           ElfW (Sym) *p;
  69           for (p = symtab; p < symtab_end; ++p)
  70             {
  71               const char *s = strtab + p->st_name;
  72               if (strcmp (s, sym_name) == 0)
  73                 return (void *) p->st_value;
  74             }
  75         }
  76     }
  77
  78   fprintf (stderr, "symbol '%s' not found\n", sym_name);
  79   exit (1);
  80   return 0;
  81 }
  82
  83 /* Open an elf binary file and memory map it with execution flag enabled.  */
  84 static void *
  85 load_elf (const char *libname, size_t *size, void *load_addr)
  86 {
  87   int fd;
  88   struct stat st;
  89
  90   if ((fd = open (libname, O_RDONLY)) == -1)
  91     {
  92       fprintf (stderr, "open (\"%s\", O_RDONLY): %s\n", libname,
  93                strerror (errno));
  94       exit (1);
  95     }
  96
  97   if (fstat (fd, &st) != 0)
  98     {
  99       fprintf (stderr, "fstat (\"%d\"): %s\n", fd, strerror (errno));
 100       exit (1);
 101     }
 102
 103   void *addr = mmap (load_addr, st.st_size,
 104                      PROT_READ | PROT_WRITE | PROT_EXEC,
 105                      load_addr != NULL ? MAP_PRIVATE | MAP_FIXED : MAP_PRIVATE,
 106                      fd, 0);
 107   close (fd);
 108
 109   if (addr == MAP_FAILED)
 110     {
 111       fprintf (stderr, "mmap: %s\n", strerror (errno));
 112       exit (1);
 113     }
 114
 115   if (size != NULL)
 116     *size = st.st_size;
 117
 118   return addr;
 119 }