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ash,hush: fix $RANDOM in children being repeated

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function                                             old     new   delta
next_random                                           46      68     +22
forkshell                                            248     263     +15
expand_vars_to_list                                 2118    2131     +13
run_pipe                                            1775    1782      +7
popstring                                            134     140      +6
builtin_umask                                        123     121      -2
ash_main                                            1356    1336     -20
get_local_var_value                                  125     104     -21
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 5/3 up/down: 63/-43)             Total: 20 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2009-10-12 15:25:01 +02:00
parent 3c39e702d0
commit 76ace254e1
5 changed files with 22 additions and 16 deletions
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17
shell/ash.c
View File

@ -4725,10 +4725,12 @@ forkshell(struct job *jp, union node *n, int mode)
freejob(jp);
ash_msg_and_raise_error("can't fork");
}
if (pid == 0)
if (pid == 0) {
CLEAR_RANDOM_T(&random_gen); /* or else $RANDOM repeats in child */
forkchild(jp, n, mode);
else
} else {
forkparent(jp, n, mode, pid);
}
return pid;
}
@ -10079,12 +10081,6 @@ setcmd(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
static void FAST_FUNC
change_random(const char *value)
{
/* Galois LFSR parameter */
/* Taps at 32 31 29 1: */
enum { MASK = 0x8000000b };
/* Another example - taps at 32 31 30 10: */
/* MASK = 0x00400007 */
uint32_t t;
if (value == NULL) {
@ -13268,11 +13264,6 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
#endif
rootpid = getpid();
#if ENABLE_ASH_RANDOM_SUPPORT
/* Can use monotonic_ns() for better randomness but for now it is
* not used anywhere else in busybox... so avoid bloat */
INIT_RANDOM_T(&random_gen, rootpid, monotonic_us());
#endif
init();
setstackmark(&smark);
procargs(argv);

6
shell/hush.c
View File

@ -88,6 +88,8 @@
#include "match.h"
#if ENABLE_HUSH_RANDOM_SUPPORT
# include "random.h"
#else
# define CLEAR_RANDOM_T(rnd) ((void)0)
#endif
#ifndef PIPE_BUF
# define PIPE_BUF 4096 /* amount of buffering in a pipe */
@ -1319,8 +1321,6 @@ static const char *get_local_var_value(const char *name)
// bash compat: UID? EUID?
#if ENABLE_HUSH_RANDOM_SUPPORT
if (strcmp(name, "RANDOM") == 0) {
if (G.random_gen.galois_LFSR == 0)
INIT_RANDOM_T(&G.random_gen, G.root_pid, monotonic_us());
return utoa(next_random(&G.random_gen));
}
#endif
@ -4000,6 +4000,7 @@ static NOINLINE int run_pipe(struct pipe *pi)
if (!command->pid) { /* child */
#if ENABLE_HUSH_JOB
disable_restore_tty_pgrp_on_exit();
CLEAR_RANDOM_T(&G.random_gen); /* or else $RANDOM repeats in child */
/* Every child adds itself to new process group
* with pgid == pid_of_first_child_in_pipe */
@ -5207,6 +5208,7 @@ static FILE *generate_stream_from_string(const char *s)
+ (1 << SIGTTIN)
+ (1 << SIGTTOU)
, SIG_IGN);
CLEAR_RANDOM_T(&G.random_gen); /* or else $RANDOM repeats in child */
close(channel[0]); /* NB: close _first_, then move fd! */
xmove_fd(channel[1], 1);
/* Prevent it from trying to handle ctrl-z etc */

2
shell/math.c
View File

@ -258,7 +258,7 @@ static int
arith_lookup_val(v_n_t *t, a_e_h_t *math_hooks)
{
if (t->var) {
const char * p = lookupvar(t->var);
const char *p = lookupvar(t->var);
if (p) {
int errcode;

7
shell/random.c
View File

@ -20,6 +20,13 @@ next_random(random_t *rnd)
uint32_t t;
if (UNINITED_RANDOM_T(rnd)) {
/* Can use monotonic_ns() for better randomness but for now
* it is not used anywhere else in busybox... so avoid bloat
*/
INIT_RANDOM_T(rnd, getpid(), monotonic_us());
}
/* LCG has period of 2^32 and alternating lowest bit */
rnd->LCG = 1664525 * rnd->LCG + 1013904223;
/* Galois LFSR has period of 2^32-1 = 3 * 5 * 17 * 257 * 65537 */

6
shell/random.h
View File

@ -13,7 +13,13 @@ typedef struct random_t {
uint32_t LCG; /* LCG (fast but weak) */
} random_t;
#define UNINITED_RANDOM_T(rnd) \
((rnd)->galois_LFSR == 0)
#define INIT_RANDOM_T(rnd, nonzero, v) \
((rnd)->galois_LFSR = (nonzero), (rnd)->LCG = (v))
#define CLEAR_RANDOM_T(rnd) \
((rnd)->galois_LFSR = 0)
uint32_t next_random(random_t *rnd) FAST_FUNC;