/usr/src/gnu/usr.bin/binutils/gdb/fork-child.c

Bug Summary

File:	src/gnu/usr.bin/binutils/gdb/fork-child.c
Warning:	line 294, column 23 This function call is prohibited after a successful vfork

Annotated Source Code

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clang -cc1 -cc1 -triple amd64-unknown-openbsd7.0 -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name fork-child.c -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -mrelocation-model pic -pic-level 1 -pic-is-pie -mframe-pointer=all -relaxed-aliasing -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -target-feature +retpoline-indirect-calls -target-feature +retpoline-indirect-branches -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/usr/src/gnu/usr.bin/binutils/obj/gdb -resource-dir /usr/local/lib/clang/13.0.0 -D PIE_DEFAULT=1 -I . -I /usr/src/gnu/usr.bin/binutils/gdb -I /usr/src/gnu/usr.bin/binutils/gdb/config -D LOCALEDIR="/usr/share/locale" -D HAVE_CONFIG_H -I /usr/src/gnu/usr.bin/binutils/gdb/../include/opcode -I ../bfd -I /usr/src/gnu/usr.bin/binutils/gdb/../bfd -I /usr/src/gnu/usr.bin/binutils/gdb/../include -I ../intl -I /usr/src/gnu/usr.bin/binutils/gdb/../intl -D MI_OUT=1 -D TUI=1 -internal-isystem /usr/local/lib/clang/13.0.0/include -internal-externc-isystem /usr/include -O2 -fdebug-compilation-dir=/usr/src/gnu/usr.bin/binutils/obj/gdb -ferror-limit 19 -fwrapv -D_RET_PROTECTOR -ret-protector -fgnuc-version=4.2.1 -fcommon -vectorize-loops -vectorize-slp -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-valloc -fno-builtin-free -fno-builtin-strdup -fno-builtin-strndup -analyzer-output=html -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /home/ben/Projects/vmm/scan-build/2022-01-12-194120-40624-1 -x c /usr/src/gnu/usr.bin/binutils/gdb/fork-child.c

1/* Fork a Unix child process, and set up to debug it, for GDB.

 Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999,
 2000, 2001, 2004 Free Software Foundation, Inc.

 Contributed by Cygnus Support.

 This file is part of GDB.

 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 2 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, write to the Free Software
 Foundation, Inc., 59 Temple Place - Suite 330,
 Boston, MA 02111-1307, USA.  */

25#include "defs.h"
26#include "gdb_string.h"
27#include "frame.h"		/* required by inferior.h */
28#include "inferior.h"
29#include "target.h"
30#include "gdb_wait.h"
31#include "gdb_vfork.h"
32#include "gdbcore.h"
33#include "terminal.h"
34#include "gdbthread.h"
35#include "command.h" /* for dont_repeat () */

37#include <signal.h>

39/* This just gets used as a default if we can't find SHELL.  */
40#ifndef SHELL_FILE"/bin/sh"
41#define SHELL_FILE"/bin/sh" "/bin/sh"
42#endif

44extern char **environ;

46/* Break up SCRATCH into an argument vector suitable for passing to
 execvp and store it in ARGV.  E.g., on "run a b c d" this routine
 would get as input the string "a b c d", and as output it would
 fill in ARGV with the four arguments "a", "b", "c", "d".  */

51static void
52breakup_args (char *scratch, char **argv)
53{
char *cp = scratch;

for (;;)
  {
    /* Scan past leading separators */
    while (*cp == ' ' || *cp == '\t' || *cp == '\n')
cp++;

    /* Break if at end of string.  */
    if (*cp == '\0')
break;

    /* Take an arg.  */
    *argv++ = cp;

    /* Scan for next arg separator.  */
    cp = strchr (cp, ' ');
    if (cp == NULL((void*)0))
cp = strchr (cp, '\t');
    if (cp == NULL((void*)0))
cp = strchr (cp, '\n');

    /* No separators => end of string => break.  */
    if (cp == NULL((void*)0))
break;

    /* Replace the separator with a terminator.  */
    *cp++ = '\0';
  }

/* Null-terminate the vector.  */
*argv = NULL((void*)0);
86}

88/* When executing a command under the given shell, return non-zero if
 the '!' character should be escaped when embedded in a quoted
 command-line argument.  */

92static int
93escape_bang_in_quoted_argument (const char *shell_file)
94{
const int shell_file_len = strlen (shell_file);

/* Bang should be escaped only in C Shells.  For now, simply check
   that the shell name ends with 'csh', which covers at least csh
   and tcsh.  This should be good enough for now.  */

if (shell_file_len < 3)
  return 0;

if (shell_file[shell_file_len - 3] == 'c'
    && shell_file[shell_file_len - 2] == 's'
    && shell_file[shell_file_len - 1] == 'h')
  return 1;

return 0;
110}

112/* Start an inferior Unix child process and sets inferior_ptid to its
 pid.  EXEC_FILE is the file to run.  ALLARGS is a string containing
 the arguments to the program.  ENV is the environment vector to
 pass.  SHELL_FILE is the shell file, or NULL if we should pick
 one.  */

118/* This function is NOT reentrant.  Some of the variables have been
 made static to ensure that they survive the vfork call.  */

121void
122fork_inferior (char *exec_file_arg, char *allargs, char **env,
      void (*traceme_fun) (void), void (*init_trace_fun) (int),
      void (*pre_trace_fun) (void), char *shell_file_arg)
125{
int pid;
char *shell_command;
static char default_shell_file[] = SHELL_FILE"/bin/sh";
int len;
/* Set debug_fork then attach to the child while it sleeps, to debug. */
static int debug_fork = 0;
/* This is set to the result of setpgrp, which if vforked, will be visible
   to you in the parent process.  It's only used by humans for debugging.  */
static int debug_setpgrp = 657473;
static char *shell_file;
static char *exec_file;
char **save_our_env;
int shell = 0;
static char **argv;

/* If no exec file handed to us, get it from the exec-file command
   -- with a good, common error message if none is specified.  */
exec_file = exec_file_arg;
if (exec_file == 0)
1
Assuming 'exec_file' is not equal to null→
2
←
Taking false branch→
  exec_file = get_exec_file (1);

/* STARTUP_WITH_SHELL is defined in inferior.h.  If 0,e we'll just
  do a fork/exec, no shell, so don't bother figuring out what
  shell.  */
shell_file = shell_file_arg;
if (STARTUP_WITH_SHELL1)
3
←
Taking true branch→
  {
    /* Figure out what shell to start up the user program under.  */
    if (shell_file == NULL((void*)0))
4
←
Assuming 'shell_file' is not equal to NULL→
5
←
Taking false branch→
shell_file = getenv ("SHELL");
    if (shell_file5.1
'shell_file' is not equal to NULL
 == NULL((void*)0))
6
←
Taking false branch→
shell_file = default_shell_file;
    shell = 1;
  }

/* Multiplying the length of exec_file by 4 is to account for the
   fact that it may expand when quoted; it is a worst-case number
   based on every character being '.  */
len = 5 + 4 * strlen (exec_file) + 1 + strlen (allargs) + 1 + /*slop */ 12;
/* If desired, concat something onto the front of ALLARGS.
   SHELL_COMMAND is the result.  */
167#ifdef SHELL_COMMAND_CONCAT
shell_command = (char *) alloca (strlen (SHELL_COMMAND_CONCAT) + len)__builtin_alloca(strlen (SHELL_COMMAND_CONCAT) + len);
strcpy (shell_command, SHELL_COMMAND_CONCAT);
170#else
shell_command = (char *) alloca (len)__builtin_alloca(len);
shell_command[0] = '\0';
173#endif

if (!shell6.1
'shell' is 1
)
7
←
Taking false branch→
  {
    /* We're going to call execvp.  Create argument vector.
Calculate an upper bound on the length of the vector by
assuming that every other character is a separate
argument.  */
    int argc = (strlen (allargs) + 1) / 2 + 2;
    argv = (char **) xmalloc (argc * sizeof (*argv));
    argv[0] = exec_file;
    breakup_args (allargs, &argv[1]);
  }
else
  {
    /* We're going to call a shell.  */

    /* Now add exec_file, quoting as necessary.  */

    char *p;
    int need_to_quote;
    const int escape_bang = escape_bang_in_quoted_argument (shell_file);

    strcat (shell_command, "exec ");

    /* Quoting in this style is said to work with all shells.  But
       csh on IRIX 4.0.1 can't deal with it.  So we only quote it if
       we need to.  */
    p = exec_file;
    while (1)
8
←
Loop condition is true.  Entering loop body→
{
 switch (*p)
9
←
Control jumps to 'case 0:'  at line 222→
   {
   case '\'':
   case '!':
   case '"':
   case '(':
   case ')':
   case '$':
   case '&':
   case ';':
   case '<':
   case '>':
   case ' ':
   case '\n':
   case '\t':
     need_to_quote = 1;
     goto end_scan;

   case '\0':
     need_to_quote = 0;
     goto end_scan;
10
←
Control jumps to line 232→

   default:
     break;
   }
 ++p;
}
  end_scan:
    if (need_to_quote10.1
'need_to_quote' is 0
)
11
←
Taking false branch→
{
 strcat (shell_command, "'");
 for (p = exec_file; *p != '\0'; ++p)
   {
     if (*p == '\'')
strcat (shell_command, "'\\''");
     else if (*p == '!' && escape_bang)
strcat (shell_command, "\\!");
     else
strncat (shell_command, p, 1);
   }
 strcat (shell_command, "'");
}
    else
strcat (shell_command, exec_file);

    strcat (shell_command, " ");
    strcat (shell_command, allargs);
  }

/* On some systems an exec will fail if the executable is open.  */
close_exec_file ();

/* Retain a copy of our environment variables, since the child will
   replace the value of environ and if we're vforked, we have to
   restore it.  */
save_our_env = environ;

/* Tell the terminal handling subsystem what tty we plan to run on;
   it will just record the information for later.  */
new_tty_prefork (inferior_io_terminal);

/* It is generally good practice to flush any possible pending stdio
   output prior to doing a fork, to avoid the possibility of both
   the parent and child flushing the same data after the fork. */
gdb_flush (gdb_stdout);
gdb_flush (gdb_stderr);

/* If there's any initialization of the target layers that must
   happen to prepare to handle the child we're about fork, do it
   now...  */
if (pre_trace_fun != NULL((void*)0))
12
←
Assuming 'pre_trace_fun' is equal to NULL→
13
←
Taking false branch→
  (*pre_trace_fun) ();

/* Create the child process.  Note that the apparent call to vfork()
   below *might* actually be a call to fork() due to the fact that
   autoconf will ``#define vfork fork'' on certain platforms.  */
if (debug_fork13.1
'debug_fork' is 0
)
14
←
Taking false branch→
  pid = fork ();
else
  pid = vfork ();

if (pid14.1
'pid' is >= 0
 < 0)
15
←
Taking false branch→
  perror_with_name ("vfork");

if (pid15.1
'pid' is equal to 0
 == 0)
16
←
Taking true branch→
  {
    if (debug_fork16.1
'debug_fork' is 0
)
17
←
Taking false branch→
sleep (debug_fork);

    /* Run inferior in a separate process group.  */
    debug_setpgrp = gdb_setpgid ();
18
←
This function call is prohibited after a successful vfork
    if (debug_setpgrp == -1)
perror ("setpgrp failed in child");

    /* Ask the tty subsystem to switch to the one we specified
       earlier (or to share the current terminal, if none was
       specified).  */
    new_tty ();

    /* Changing the signal handlers for the inferior after
       a vfork can also change them for the superior, so we don't mess
       with signals here.  See comments in
       initialize_signals for how we get the right signal handlers
       for the inferior.  */

    /* "Trace me, Dr. Memory!" */
    (*traceme_fun) ();

    /* The call above set this process (the "child") as debuggable
      by the original gdb process (the "parent").  Since processes
      (unlike people) can have only one parent, if you are debugging
      gdb itself (and your debugger is thus _already_ the
      controller/parent for this child), code from here on out is
      undebuggable.  Indeed, you probably got an error message
      saying "not parent".  Sorry; you'll have to use print
      statements!  */

    /* There is no execlpe call, so we have to set the environment
       for our child in the global variable.  If we've vforked, this
       clobbers the parent, but environ is restored a few lines down
       in the parent.  By the way, yes we do need to look down the
       path to find $SHELL.  Rich Pixley says so, and I agree.  */
    environ = env;

    /* If we decided above to start up with a shell, we exec the
      shell, "-c" says to interpret the next arg as a shell command
      to execute, and this command is "exec <target-program>
      <args>".  "-f" means "fast startup" to the c-shell, which
      means don't do .cshrc file. Doing .cshrc may cause fork/exec
      events which will confuse debugger start-up code.  */
    if (shell)
{
 execlp (shell_file, shell_file, "-c", shell_command, (char *) 0);

 /* If we get here, it's an error.  */
 fprintf_unfiltered (gdb_stderr, "Cannot exec %s: %s.\n", shell_file,
	      safe_strerror (errno(*__errno())));
 gdb_flush (gdb_stderr);
 _exit (0177);
}
    else
{
 /* Otherwise, we directly exec the target program with
    execvp.  */
 int i;
 char *errstring;

 execvp (exec_file, argv);

 /* If we get here, it's an error.  */
 errstring = safe_strerror (errno(*__errno()));
 fprintf_unfiltered (gdb_stderr, "Cannot exec %s ", exec_file);

 i = 1;
 while (argv[i] != NULL((void*)0))
   {
     if (i != 1)
fprintf_unfiltered (gdb_stderr, " ");
     fprintf_unfiltered (gdb_stderr, "%s", argv[i]);
     i++;
   }
 fprintf_unfiltered (gdb_stderr, ".\n");
366#if 0
 /* This extra info seems to be useless.  */
 fprintf_unfiltered (gdb_stderr, "Got error %s.\n", errstring);
369#endif
 gdb_flush (gdb_stderr);
 _exit (0177);
}
  }

/* Restore our environment in case a vforked child clob'd it.  */
environ = save_our_env;

init_thread_list ();

/* Needed for wait_for_inferior stuff below.  */
inferior_ptid = pid_to_ptid (pid);

/* Now that we have a child process, make it our target, and
   initialize anything target-vector-specific that needs
   initializing.  */
(*init_trace_fun) (pid);

/* We are now in the child process of interest, having exec'd the
   correct program, and are poised at the first instruction of the
   new program.  */

/* Allow target dependent code to play with the new process.  This
   might be used to have target-specific code initialize a variable
   in the new process prior to executing the first instruction.  */
TARGET_CREATE_INFERIOR_HOOK (pid);

397#ifdef SOLIB_CREATE_INFERIOR_HOOK
SOLIB_CREATE_INFERIOR_HOOK (pid)solib_create_inferior_hook();
399#endif
400}

402/* Accept NTRAPS traps from the inferior.  */

404void
405startup_inferior (int ntraps)
406{
int pending_execs = ntraps;
int terminal_initted = 0;

/* The process was started by the fork that created it, but it will
   have stopped one instruction after execing the shell.  Here we
   must get it up to actual execution of the real program.  */

clear_proceed_status ();

init_wait_for_inferior ();

if (STARTUP_WITH_SHELL1)
  inferior_ignoring_startup_exec_events = ntraps;
else
  inferior_ignoring_startup_exec_events = 0;
inferior_ignoring_leading_exec_events =
  target_reported_exec_events_per_exec_call ()(*current_target.to_reported_exec_events_per_exec_call) () - 1;

while (1)
  {
    /* Make wait_for_inferior be quiet. */
    stop_soon = STOP_QUIETLY;
    wait_for_inferior ();
    if (stop_signal != TARGET_SIGNAL_TRAP)
{
 /* Let shell child handle its own signals in its own way.
    FIXME: what if child has exited?  Must exit loop
    somehow.  */
 resume (0, stop_signal);
}
    else
{
 /* We handle SIGTRAP, however; it means child did an exec.  */
 if (!terminal_initted)
   {
     /* Now that the child has exec'd we know it has already
        set its process group.  On POSIX systems, tcsetpgrp
        will fail with EPERM if we try it before the child's
        setpgid.  */

     /* Set up the "saved terminal modes" of the inferior
        based on what modes we are starting it with.  */
     target_terminal_init ()(*current_target.to_terminal_init) ();

     /* Install inferior's terminal modes.  */
     target_terminal_inferior ()(*current_target.to_terminal_inferior) ();

     terminal_initted = 1;
   }

 if (--pending_execs == 0)
   break;

 resume (0, TARGET_SIGNAL_0);	/* Just make it go on.  */
}
  }
stop_soon = NO_STOP_QUIETLY;
464}