Add helper binary `exec1'

* .gitignore: New files.
* Makefile.in (mostlyclean_dirs): Add libexec, if its Makefile
exists.
* autogen.sh (do_git): Autoreconf in exec as well.
* configure.ac: Configure libexec on Android.
* exec/Makefile.in:
* exec/README:
* exec/config-mips.m4.in:
* exec/config.guess:
* exec/config.h.in:
* exec/config.sub:
* exec/configure:
* exec/configure.ac:
* exec/deps.mk:
* exec/exec.c (MIN, struct exec_open_command)
(struct exec_map_command, struct exec_jump_command)
(write_open_command, write_load_command, process_interpreter_1)
(process_interpreter, process_program_header, insert_args)
(exec_0):
* exec/exec.h (_EXEC_H_, struct elf_header_32)
(struct program_header_32, struct dt_entry_32)
(struct elf_header_64, struct program_header_64)
(struct dt_entry_64, struct exec_tracee):
* exec/exec1.c (main):
* exec/install-sh (scriptversion):
* exec/loader-aarch64.s (_start):
* exec/loader-armeabi.s (_start):
* exec/loader-mips64el.s (__start):
* exec/loader-mipsel.s (__start):
* exec/loader-x86.s (_start):
* exec/loader-x86_64.s (_start):
* exec/mipsel-user.h (_MIPSEL_USER_H_):
* exec/mipsfpu.c (MIPS_ABI_FP_ANY, fpu_reqs, valid_abi_p)
(fp_mode_for_abi, cpu_supports_fr0_p, determine_fpu_mode):
* exec/mipsfpu.h (_MIPSFPU_H_, FP_FR0):
* exec/test.c (print_usage, main):
* exec/trace.c (MAX_TRACEES, aarch64_set_regs, read_memory)
(user_alloca, user_copy, remove_tracee, handle_clone)
(syscall_trap_p, handle_exec, process_system_call, tracing_execve)
(after_fork, find_tracee, exec_waitpid, exec_init): New files.
* java/Makefile.in (CROSS_EXEC_BINS): Add exec1 and
loader.
($(CROSS_EXEC_BINS) &): New target.

1 files changed, 88 insertions, 0 deletions

diff --git a/exec/exec1.c b/exec/exec1.c
new file mode 100644
index 00000000000..835bf8e72b9
--- /dev/null
+++ b/exec/exec1.c
@@ -0,0 +1,88 @@
+/* Program execution for Emacs.
+
+Copyright (C) 2023 Free Software Foundation, Inc.
+
+This file is part of GNU Emacs.
+
+GNU Emacs 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.
+
+GNU Emacs 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 GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+
+#include "exec.h"
+
+/* exec1 is a program which takes another program and its arguments,
+   forks, and executes that program, all while tracing it and its
+   children to use the program execution mechanism defined in exec.c.
+
+   This is necessary to bypass security restrictions which prohibit
+   Emacs from loading executables from certain directories, by, in
+   effect, replacing the executable loader in the Linux kernel.  */
+
+
+
+int
+main (int argc, char **argv)
+{
+  pid_t pid, pid1;
+  extern char **environ;
+  int wstatus;
+
+  pid = fork ();
+
+  if (!pid)
+    {
+      tracing_execve (argv[2], argv + 2, environ);
+
+      /* An error occured.  Exit with failure.  */
+      exit (127);
+    }
+  else
+    {
+      /* Provide the file name of the loader.  */
+      exec_init (argv[1]);
+
+      if (after_fork (pid))
+	exit (127);
+
+      /* Start waiting for the process to exit.  */
+
+      while (true)
+	{
+	  pid1 = exec_waitpid (-1, &wstatus, 0);
+
+	  /* If the child process exits normally, exit with its status
+	     code.  If not, raise the signal that caused it to
+	     exit.  */
+
+	  if (pid == pid1)
+	    {
+	      if (WIFEXITED (wstatus))
+		exit (WEXITSTATUS (wstatus));
+	      else /* if WIFSIGNALED (wstatus) */
+		{
+		  raise (WTERMSIG (wstatus));
+
+		  /* Just in case the signal raised doesn't cause an
+		     exit.  */
+		  exit (127);
+		}
+	    }
+
+	  /* Otherwise, continue looping.  */
+	}
+    }
+}