[gdb/testsuite] add jit-elf-util.h and run jit function

Splits ELF related symbols into a separate jit-elf-util.h header and
enhances it with a few more.

Intention is to make adding new JIT tests possible without repeating
most of the common boilerplate.

As a test enhancement, jit-elf-main.c now calls the renamed function
after registering the jit object and ensures it returns an expected
result.

gdb/testsuite/ChangeLog:

2020-02-18  Mihails Strasuns  <mihails.strasuns@intel.com>

	* gdb.base/jit-elf-util.h: New header file.
	* gdb.base/jit-elf-main.c: Use jit-elf-util.h, add a call to
	  the renamed JIT function to verify its result.

1 files changed, 118 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.base/jit-elf-util.h b/gdb/testsuite/gdb.base/jit-elf-util.h
new file mode 100644
index 00000000000..843cf306182
--- /dev/null
+++ b/gdb/testsuite/gdb.base/jit-elf-util.h
@@ -0,0 +1,118 @@
+/* This test program is part of GDB, the GNU debugger.
+
+   Copyright 2020 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.  */
+
+  for (int 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);
+
+	  for (ElfW (Sym) *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;
+}