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/* This test program is part of GDB, the GNU debugger.
Copyright 2020-2022 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* Simulates loading of JIT code by memory mapping a compiled
shared library binary and doing minimal post-processing. */
#include <elf.h>
#include <errno.h>
#include <fcntl.h>
#include <link.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
/* ElfW is coming from linux. On other platforms it does not exist.
Let us define it here. */
#ifndef ElfW
#if (defined(_LP64) || defined(__LP64__))
#define WORDSIZE 64
#else
#define WORDSIZE 32
#endif /* _LP64 || __LP64__ */
#define ElfW(type) _ElfW (Elf, WORDSIZE, type)
#define _ElfW(e, w, t) _ElfW_1 (e, w, _##t)
#define _ElfW_1(e, w, t) e##w##t
#endif /* !ElfW */
/* Find symbol with the name `sym_name`. */
static void *
load_symbol (void *addr, const char *sym_name)
{
const ElfW (Ehdr) *const ehdr = (ElfW (Ehdr) *) addr;
ElfW (Shdr) *const shdr = (ElfW (Shdr) *) ((char *) addr + ehdr->e_shoff);
ElfW (Addr) sym_old_addr = 0;
ElfW (Addr) sym_new_addr = 0;
/* Find `func_name` in symbol_table and return its address. */
int i;
for (i = 0; i < ehdr->e_shnum; ++i)
{
if (shdr[i].sh_type == SHT_SYMTAB)
{
ElfW (Sym) *symtab = (ElfW (Sym) *) (addr + shdr[i].sh_offset);
ElfW (Sym) *symtab_end
= (ElfW (Sym) *) (addr + shdr[i].sh_offset + shdr[i].sh_size);
char *const strtab
= (char *) (addr + shdr[shdr[i].sh_link].sh_offset);
ElfW (Sym) *p;
for (p = symtab; p < symtab_end; ++p)
{
const char *s = strtab + p->st_name;
if (strcmp (s, sym_name) == 0)
return (void *) p->st_value;
}
}
}
fprintf (stderr, "symbol '%s' not found\n", sym_name);
exit (1);
return 0;
}
/* Open an elf binary file and memory map it with execution flag enabled. */
static void *
load_elf (const char *libname, size_t *size, void *load_addr)
{
int fd;
struct stat st;
if ((fd = open (libname, O_RDONLY)) == -1)
{
fprintf (stderr, "open (\"%s\", O_RDONLY): %s\n", libname,
strerror (errno));
exit (1);
}
if (fstat (fd, &st) != 0)
{
fprintf (stderr, "fstat (\"%d\"): %s\n", fd, strerror (errno));
exit (1);
}
void *addr = mmap (load_addr, st.st_size,
PROT_READ | PROT_WRITE | PROT_EXEC,
load_addr != NULL ? MAP_PRIVATE | MAP_FIXED : MAP_PRIVATE,
fd, 0);
close (fd);
if (addr == MAP_FAILED)
{
fprintf (stderr, "mmap: %s\n", strerror (errno));
exit (1);
}
if (size != NULL)
*size = st.st_size;
return addr;
}
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