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hush: reinstate cmd handling for NOMMU (with fat big warning).

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hush: fix a case where none of pipe members could be started
  because of fork failure
hush: rename functions: xxx_real -> xxx
hush: try to add a bit more of vfork-friendliness
hush: add rudimentary design docs
hush: add TODO (newly discovered bug with globbing)
This commit is contained in:
Denis Vlasenko 2008-02-10 12:10:08 +00:00
parent 68e8e96d7f
commit 05743d7949
5 changed files with 166 additions and 92 deletions
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3
include/libbb.h
View File

@ -664,6 +664,9 @@ enum {
void re_exec(char **argv) ATTRIBUTE_NORETURN;
void forkexit_or_rexec(char **argv);
extern bool re_execed;
int BUG_fork_is_unavailable_on_nommu(void);
int BUG_daemon_is_unavailable_on_nommu(void);
void BUG_bb_daemonize_is_unavailable_on_nommu(void);
# define fork() BUG_fork_is_unavailable_on_nommu()
# define daemon(a,b) BUG_daemon_is_unavailable_on_nommu()
# define bb_daemonize(a) BUG_bb_daemonize_is_unavailable_on_nommu()

192
shell/hush.c
View File

@ -84,12 +84,24 @@
#include "busybox.h" /* for APPLET_IS_NOFORK/NOEXEC */
#if !BB_MMU
/* A bit drastic. Can allow some simpler commands
* by analysing command in generate_stream_from_list()
*/
#undef ENABLE_HUSH_TICK
#define ENABLE_HUSH_TICK 0
#if !BB_MMU && ENABLE_HUSH_TICK
//#undef ENABLE_HUSH_TICK
//#define ENABLE_HUSH_TICK 0
#warning On NOMMU, hush command substitution is dangerous.
#warning Dont use it for commands which produce lots of output.
#warning For more info see shell/hush.c, generate_stream_from_list().
#endif
#if !BB_MMU && ENABLE_HUSH_JOB
#undef ENABLE_HUSH_JOB
#define ENABLE_HUSH_JOB 0
#endif
#if !ENABLE_HUSH_INTERACTIVE
#undef ENABLE_FEATURE_EDITING
#define ENABLE_FEATURE_EDITING 0
#undef ENABLE_FEATURE_EDITING_FANCY_PROMPT
#define ENABLE_FEATURE_EDITING_FANCY_PROMPT 0
#endif
@ -176,13 +188,6 @@ void xxfree(void *ptr)
#endif
#if !ENABLE_HUSH_INTERACTIVE
#undef ENABLE_FEATURE_EDITING
#define ENABLE_FEATURE_EDITING 0
#undef ENABLE_FEATURE_EDITING_FANCY_PROMPT
#define ENABLE_FEATURE_EDITING_FANCY_PROMPT 0
#endif
#define SPECIAL_VAR_SYMBOL 3
#define PARSEFLAG_EXIT_FROM_LOOP 1
@ -508,10 +513,10 @@ static int free_pipe_list(struct pipe *head, int indent);
static int free_pipe(struct pipe *pi, int indent);
/* really run the final data structures: */
static int setup_redirects(struct child_prog *prog, int squirrel[]);
static int run_list_real(struct pipe *pi);
static int run_list(struct pipe *pi);
static void pseudo_exec_argv(char **argv) ATTRIBUTE_NORETURN;
static void pseudo_exec(struct child_prog *child) ATTRIBUTE_NORETURN;
static int run_pipe_real(struct pipe *pi);
static int run_pipe(struct pipe *pi);
/* extended glob support: */
static char **globhack(const char *src, char **strings);
static int glob_needed(const char *s);
@ -1416,7 +1421,7 @@ static void restore_redirects(int squirrel[])
}
}
/* Called after [v]fork() in run_pipe_real(), or from builtin_exec().
/* Called after [v]fork() in run_pipe(), or from builtin_exec().
* Never returns.
* XXX no exit() here. If you don't exec, use _exit instead.
* The at_exit handlers apparently confuse the calling process,
@ -1438,9 +1443,8 @@ static void pseudo_exec_argv(char **argv)
/* If a variable is assigned in a forest, and nobody listens,
* was it ever really set?
*/
if (argv[0] == NULL) {
if (!argv[0])
_exit(EXIT_SUCCESS);
}
argv = expand_strvec_to_strvec(argv);
@ -1484,15 +1488,15 @@ static void pseudo_exec_argv(char **argv)
_exit(1);
}
/* Called after [v]fork() in run_pipe_real()
/* Called after [v]fork() in run_pipe()
*/
static void pseudo_exec(struct child_prog *child)
{
// FIXME: buggy wrt NOMMU! Must not modify any global data
// until it does exec/_exit, but currently it does.
if (child->argv) {
// until it does exec/_exit, but currently it does
// (puts malloc'ed stuff into environment)
if (child->argv)
pseudo_exec_argv(child->argv);
}
if (child->group) {
#if !BB_MMU
@ -1501,11 +1505,12 @@ static void pseudo_exec(struct child_prog *child)
int rcode;
#if ENABLE_HUSH_INTERACTIVE
debug_printf_exec("pseudo_exec: setting interactive_fd=0\n");
interactive_fd = 0; /* crucial!!!! */
// run_list_level now takes care of it?
// debug_printf_exec("pseudo_exec: setting interactive_fd=0\n");
// interactive_fd = 0; /* crucial!!!! */
#endif
debug_printf_exec("pseudo_exec: run_list_real\n");
rcode = run_list_real(child->group);
debug_printf_exec("pseudo_exec: run_list\n");
rcode = run_list(child->group);
/* OK to leak memory by not calling free_pipe_list,
* since this process is about to exit */
_exit(rcode);
@ -1672,7 +1677,7 @@ static int checkjobs(struct pipe* fg_pipe)
if (dead) {
fg_pipe->progs[i].pid = 0;
fg_pipe->running_progs--;
if (i == fg_pipe->num_progs-1)
if (i == fg_pipe->num_progs - 1)
/* last process gives overall exitstatus */
rcode = WEXITSTATUS(status);
} else {
@ -1753,13 +1758,13 @@ static int checkjobs_and_fg_shell(struct pipe* fg_pipe)
}
#endif
/* run_pipe_real() starts all the jobs, but doesn't wait for anything
/* run_pipe() starts all the jobs, but doesn't wait for anything
* to finish. See checkjobs().
*
* return code is normally -1, when the caller has to wait for children
* to finish to determine the exit status of the pipe. If the pipe
* is a simple builtin command, however, the action is done by the
* time run_pipe_real returns, and the exit code is provided as the
* time run_pipe returns, and the exit code is provided as the
* return value.
*
* The input of the pipe is always stdin, the output is always
@ -1772,7 +1777,7 @@ static int checkjobs_and_fg_shell(struct pipe* fg_pipe)
* Returns -1 only if started some children. IOW: we have to
* mask out retvals of builtins etc with 0xff!
*/
static int run_pipe_real(struct pipe *pi)
static int run_pipe(struct pipe *pi)
{
int i;
int nextin;
@ -1785,7 +1790,7 @@ static int run_pipe_real(struct pipe *pi)
int rcode;
const int single_fg = (pi->num_progs == 1 && pi->followup != PIPE_BG);
debug_printf_exec("run_pipe_real start: single_fg=%d\n", single_fg);
debug_printf_exec("run_pipe start: single_fg=%d\n", single_fg);
#if ENABLE_HUSH_JOB
pi->pgrp = -1;
@ -1801,11 +1806,11 @@ static int run_pipe_real(struct pipe *pi)
if (single_fg && child->group && child->subshell == 0) {
debug_printf("non-subshell grouping\n");
setup_redirects(child, squirrel);
debug_printf_exec(": run_list_real\n");
rcode = run_list_real(child->group);
debug_printf_exec(": run_list\n");
rcode = run_list(child->group) & 0xff;
restore_redirects(squirrel);
debug_printf_exec("run_pipe_real return %d\n", rcode);
return rcode; // do we need to add '... & 0xff' ?
debug_printf_exec("run_pipe return %d\n", rcode);
return rcode;
}
if (single_fg && child->argv != NULL) {
@ -1847,7 +1852,7 @@ static int run_pipe_real(struct pipe *pi)
rcode = x->function(argv_expanded) & 0xff;
free(argv_expanded);
restore_redirects(squirrel);
debug_printf_exec("run_pipe_real return %d\n", rcode);
debug_printf_exec("run_pipe return %d\n", rcode);
return rcode;
}
}
@ -1864,7 +1869,7 @@ static int run_pipe_real(struct pipe *pi)
rcode = run_nofork_applet_prime(&nofork_save, a, argv_expanded) & 0xff;
free(argv_expanded);
restore_redirects(squirrel);
debug_printf_exec("run_pipe_real return %d\n", rcode);
debug_printf_exec("run_pipe return %d\n", rcode);
return rcode;
}
}
@ -1892,24 +1897,22 @@ static int run_pipe_real(struct pipe *pi)
if ((i + 1) < pi->num_progs)
xpipe(pipefds);
#if BB_MMU
child->pid = fork();
#else
child->pid = vfork();
#endif
child->pid = BB_MMU ? fork() : vfork();
if (!child->pid) { /* child */
#if ENABLE_HUSH_JOB
/* Every child adds itself to new process group
* with pgid == pid of first child in pipe */
* with pgid == pid_of_first_child_in_pipe */
if (run_list_level == 1 && interactive_fd) {
pid_t pgrp;
/* Don't do pgrp restore anymore on fatal signals */
set_fatal_sighandler(SIG_DFL);
if (pi->pgrp < 0) /* true for 1st process only */
pi->pgrp = getpid();
if (setpgid(0, pi->pgrp) == 0 && pi->followup != PIPE_BG) {
pgrp = pi->pgrp;
if (pgrp < 0) /* true for 1st process only */
pgrp = getpid();
if (setpgid(0, pgrp) == 0 && pi->followup != PIPE_BG) {
/* We do it in *every* child, not just first,
* to avoid races */
tcsetpgrp(interactive_fd, pi->pgrp);
tcsetpgrp(interactive_fd, pgrp);
}
}
#endif
@ -1930,7 +1933,7 @@ static int run_pipe_real(struct pipe *pi)
if (child->pid < 0) { /* [v]fork failed */
/* Clearly indicate, was it fork or vfork */
bb_perror_msg(BB_MMU ? "cannot fork" : "cannot vfork");
bb_perror_msg(BB_MMU ? "fork" : "vfork");
} else {
pi->running_progs++;
#if ENABLE_HUSH_JOB
@ -1948,7 +1951,12 @@ static int run_pipe_real(struct pipe *pi)
nextin = pipefds[0];
}
debug_printf_exec("run_pipe_real return -1\n");
if (!pi->running_progs) {
debug_printf_exec("run_pipe return 1 (all forks failed, no children)\n");
return 1;
}
debug_printf_exec("run_pipe return -1 (%u children started)\n", pi->running_progs);
return -1;
}
@ -2017,7 +2025,7 @@ static void debug_print_tree(struct pipe *pi, int lvl)
/* NB: called by pseudo_exec, and therefore must not modify any
* global data until exec/_exit (we can be a child after vfork!) */
static int run_list_real(struct pipe *pi)
static int run_list(struct pipe *pi)
{
struct pipe *rpipe;
#if ENABLE_HUSH_LOOPS
@ -2026,7 +2034,6 @@ static int run_list_real(struct pipe *pi)
char **for_list = NULL;
int flag_rep = 0;
#endif
int save_num_progs;
int flag_skip = 1;
int rcode = 0; /* probably for gcc only */
int flag_restore = 0;
@ -2038,7 +2045,7 @@ static int run_list_real(struct pipe *pi)
reserved_style rword;
reserved_style skip_more_for_this_rword = RES_XXXX;
debug_printf_exec("run_list_real start lvl %d\n", run_list_level + 1);
debug_printf_exec("run_list start lvl %d\n", run_list_level + 1);
#if ENABLE_HUSH_LOOPS
/* check syntax for "for" */
@ -2047,7 +2054,7 @@ static int run_list_real(struct pipe *pi)
&& (rpipe->next == NULL)
) {
syntax("malformed for"); /* no IN or no commands after IN */
debug_printf_exec("run_list_real lvl %d return 1\n", run_list_level);
debug_printf_exec("run_list lvl %d return 1\n", run_list_level);
return 1;
}
if ((rpipe->res_word == RES_IN && rpipe->next->res_word == RES_IN && rpipe->next->progs[0].argv != NULL)
@ -2055,7 +2062,7 @@ static int run_list_real(struct pipe *pi)
) {
/* TODO: what is tested in the first condition? */
syntax("malformed for"); /* 2nd condition: not followed by IN */
debug_printf_exec("run_list_real lvl %d return 1\n", run_list_level);
debug_printf_exec("run_list lvl %d return 1\n", run_list_level);
return 1;
}
}
@ -2103,9 +2110,10 @@ static int run_list_real(struct pipe *pi)
signal_SA_RESTART(SIGTSTP, handler_ctrl_z);
signal(SIGINT, handler_ctrl_c);
}
#endif
#endif /* JOB */
for (; pi; pi = flag_restore ? rpipe : pi->next) {
//why? int save_num_progs;
rword = pi->res_word;
#if ENABLE_HUSH_LOOPS
if (rword == RES_WHILE || rword == RES_UNTIL || rword == RES_FOR) {
@ -2178,12 +2186,12 @@ static int run_list_real(struct pipe *pi)
#endif
if (pi->num_progs == 0)
continue;
save_num_progs = pi->num_progs; /* save number of programs */
debug_printf_exec(": run_pipe_real with %d members\n", pi->num_progs);
rcode = run_pipe_real(pi);
//why? save_num_progs = pi->num_progs;
debug_printf_exec(": run_pipe with %d members\n", pi->num_progs);
rcode = run_pipe(pi);
if (rcode != -1) {
/* We only ran a builtin: rcode was set by the return value
* of run_pipe_real(), and we don't need to wait for anything. */
* of run_pipe(), and we don't need to wait for anything. */
} else if (pi->followup == PIPE_BG) {
/* What does bash do with attempts to background builtins? */
/* Even bash 3.2 doesn't do that well with nested bg:
@ -2196,7 +2204,6 @@ static int run_list_real(struct pipe *pi)
rcode = EXIT_SUCCESS;
} else {
#if ENABLE_HUSH_JOB
/* Paranoia, just "interactive_fd" should be enough? */
if (run_list_level == 1 && interactive_fd) {
/* waits for completion, then fg's main shell */
rcode = checkjobs_and_fg_shell(pi);
@ -2210,7 +2217,7 @@ static int run_list_real(struct pipe *pi)
}
debug_printf_exec(": setting last_return_code=%d\n", rcode);
last_return_code = rcode;
pi->num_progs = save_num_progs; /* restore number of programs */
//why? pi->num_progs = save_num_progs;
#if ENABLE_HUSH_IF
if (rword == RES_IF || rword == RES_ELIF)
next_if_code = rcode; /* can be overwritten a number of times */
@ -2241,7 +2248,7 @@ static int run_list_real(struct pipe *pi)
signal(SIGINT, SIG_IGN);
}
#endif
debug_printf_exec("run_list_real lvl %d return %d\n", run_list_level + 1, rcode);
debug_printf_exec("run_list lvl %d return %d\n", run_list_level + 1, rcode);
return rcode;
}
@ -2315,19 +2322,19 @@ static int free_pipe_list(struct pipe *head, int indent)
}
/* Select which version we will use */
static int run_list(struct pipe *pi)
static int run_and_free_list(struct pipe *pi)
{
int rcode = 0;
debug_printf_exec("run_list entered\n");
if (fake_mode == 0) {
debug_printf_exec(": run_list_real with %d members\n", pi->num_progs);
rcode = run_list_real(pi);
debug_printf_exec("run_and_free_list entered\n");
if (!fake_mode) {
debug_printf_exec(": run_list with %d members\n", pi->num_progs);
rcode = run_list(pi);
}
/* free_pipe_list has the side effect of clearing memory.
* In the long run that function can be merged with run_list_real,
* In the long run that function can be merged with run_list,
* but doing that now would hobble the debugging effort. */
free_pipe_list(pi, 0);
debug_printf_exec("run_list return %d\n", rcode);
free_pipe_list(pi, /* indent: */ 0);
debug_printf_exec("run_nad_free_list return %d\n", rcode);
return rcode;
}
@ -3221,15 +3228,17 @@ static FILE *generate_stream_from_list(struct pipe *head)
int pid, channel[2];
xpipe(channel);
pid = fork();
if (pid < 0) {
bb_perror_msg_and_die("fork");
} else if (pid == 0) {
/* *** NOMMU WARNING *** */
/* By using vfork here, we suspend parent till child exits or execs.
* If child will not do it before it fills the pipe, it can block forever
* in write(STDOUT_FILENO), and parent (shell) will be also stuck.
*/
pid = BB_MMU ? fork() : vfork();
if (pid < 0)
bb_perror_msg_and_die(BB_MMU ? "fork" : "vfork");
if (pid == 0) { /* child */
close(channel[0]);
if (channel[1] != 1) {
dup2(channel[1], 1);
close(channel[1]);
}
xmove_fd(channel[1], 1);
/* Prevent it from trying to handle ctrl-z etc */
#if ENABLE_HUSH_JOB
run_list_level = 1;
@ -3241,11 +3250,12 @@ static FILE *generate_stream_from_list(struct pipe *head)
* everywhere outside actual command execution. */
/*set_jobctrl_sighandler(SIG_IGN);*/
set_misc_sighandler(SIG_DFL);
_exit(run_list_real(head)); /* leaks memory */
_exit(run_list(head)); /* leaks memory */
}
close(channel[1]);
pf = fdopen(channel[0], "r");
return pf;
/* head is freed by the caller */
}
/* Return code is exit status of the process that is run. */
@ -3269,7 +3279,8 @@ static int process_command_subs(o_string *dest, struct p_context *ctx,
b_free(&result);
p = generate_stream_from_list(inner.list_head);
if (p == NULL) return 1;
if (p == NULL)
return 1;
close_on_exec_on(fileno(p));
setup_file_in_str(&pipe_str, p);
@ -3294,7 +3305,7 @@ static int process_command_subs(o_string *dest, struct p_context *ctx,
* at the same time. That would be a lot of work, and contrary
* to the KISS philosophy of this program. */
retcode = fclose(p);
free_pipe_list(inner.list_head, 0);
free_pipe_list(inner.list_head, /* indent: */ 0);
debug_printf("closed FILE from child, retcode=%d\n", retcode);
return retcode;
}
@ -3674,8 +3685,8 @@ static int parse_and_run_stream(struct in_str *inp, int parse_flag)
done_word(&temp, &ctx);
done_pipe(&ctx, PIPE_SEQ);
debug_print_tree(ctx.list_head, 0);
debug_printf_exec("parse_stream_outer: run_list\n");
run_list(ctx.list_head);
debug_printf_exec("parse_stream_outer: run_and_free_list\n");
run_and_free_list(ctx.list_head);
} else {
if (ctx.old_flag != 0) {
free(ctx.stack);
@ -3684,7 +3695,7 @@ static int parse_and_run_stream(struct in_str *inp, int parse_flag)
temp.nonnull = 0;
temp.o_quote = 0;
inp->p = NULL;
free_pipe_list(ctx.list_head, 0);
free_pipe_list(ctx.list_head, /* indent: */ 0);
}
b_free(&temp);
} while (rcode != -1 && !(parse_flag & PARSEFLAG_EXIT_FROM_LOOP)); /* loop on syntax errors, return on EOF */
@ -3898,15 +3909,14 @@ int hush_main(int argc, char **argv)
if (argv[optind] == NULL) {
opt = parse_and_run_file(stdin);
goto final_return;
} else {
debug_printf("\nrunning script '%s'\n", argv[optind]);
global_argv = argv + optind;
global_argc = argc - optind;
input = xfopen(argv[optind], "r");
opt = parse_and_run_file(input);
}
debug_printf("\nrunning script '%s'\n", argv[optind]);
global_argv = argv + optind;
global_argc = argc - optind;
input = xfopen(argv[optind], "r");
opt = parse_and_run_file(input);
final_return:
#if ENABLE_FEATURE_CLEAN_UP

39
shell/hush_doc.txt Normal file
View File

@ -0,0 +1,39 @@
This is how hush runs commands:
/* callsite: process_command_subs */
generate_stream_from_list(struct pipe *head) - handles `cmds`
create UNIX pipe
[v]fork
child:
redirect pipe output to stdout
_exit(run_list(head)); /* leaks memory */
parent:
return UNIX pipe's output fd
/* head is freed by the caller */
/* callsite: parse_and_run_stream */
run_and_free_list(struct pipe *)
run_list(struct pipe *)
free_pipe_list(struct pipe *)
/* callsites: generate_stream_from_list, run_and_free_list, pseudo_exec, run_pipe */
run_list(struct pipe *) - handles "cmd; cmd2 && cmd3", while/for/do loops
run_pipe - for every pipe in list
/* callsite: run_list */
run_pipe - runs "cmd1 | cmd2 | cmd3 [&]"
run_list - used if only one cmd and it is of the form "{ cmd4; cmd5 && cmd6; }"
forks for every cmd if more than one cmd or if & is there
pseudo_exec - runs each "cmdN" (handles builtins etc)
/* callsite: run_pipe_real */
pseudo_exec - runs "cmd" (handles builtins etc)
exec - execs external programs
run_list - used if cmdN is "(cmds)" or "{cmds;}"
/* problem: putenv's malloced strings into environ -
** with vfork they will leak into parent process
*/
/* problem with ENABLE_FEATURE_SH_STANDALONE:
** run_applet_no_and_exit(a, argv) uses exit - this can interfere
** with vfork - switch to _exit there?
*/

5
shell/hush_test/run-all
View File

@ -1,6 +1,9 @@
#!/bin/sh
test -x hush || { echo "No ./hush?!"; exit; }
test -x hush || {
echo "No ./hush?! Perhaps you want to run 'ln -s ../../busybox hush'"
exit
}
PATH="$PWD:$PATH" # for hush and recho/zecho/printenv
export PATH

19
shell/hush_test/zbad2 Normal file
View File

@ -0,0 +1,19 @@
## TODO: fix and add to testsuite
## # bash zbad2
## ZVAR=z.map
## *.map
## # hush zbad2
## ZVAR=z.map
## z.map <====== !!!
## hush does globbing for "VAR=val" too!
## it should do it only for non-assignments.
## even if word looks like assignment, it can be non-assignemnt:
## ZVAR=*.map /bin/echo ZVAR=*.map
## ^dont_glob ^glob
>ZVAR=z.map
ZVAR=*.map /bin/echo ZVAR=*.map
ZVAR=*.map
echo "$ZVAR"