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In original kern_execve() code, at the start of the function, it forces

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all other threads to suicide, problem is execve() could be failed, and
a failed execve() would change threaded process to unthreaded, this side
effect is unexpected.
The new code introduces a new single threading mode SINGLE_BOUNDARY, in
the mode, all threads should suspend themself at user boundary except
the singler. we can not use SINGLE_NO_EXIT because we want to start from
a clean state if execve() is successful, suspending other threads at unknown
point and later resuming them from there and forcing them to exit at user
boundary may cause the process to start from a dirty state. If execve() is
successful, current thread upgrades to SINGLE_EXIT mode and forces other
threads to suicide at user boundary, otherwise, other threads will be resumed
and their interrupted syscall will be restarted.

Reviewed by: julian
This commit is contained in:
David Xu 2004-10-06 00:40:41 +00:00
parent 326884a998
commit 906ac69d08
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=136177
3 changed files with 111 additions and 38 deletions
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58
sys/kern/kern_exec.c
View File

@ -80,6 +80,8 @@ static int sysctl_kern_usrstack(SYSCTL_HANDLER_ARGS);
static int sysctl_kern_stackprot(SYSCTL_HANDLER_ARGS);
static int kern_execve(struct thread *td, char *fname, char **argv,
char **envv, struct mac *mac_p);
static int do_execve(struct thread *td, char *fname, char **argv,
char **envv, struct mac *mac_p);
/* XXX This should be vm_size_t. */
SYSCTL_PROC(_kern, KERN_PS_STRINGS, ps_strings, CTLTYPE_ULONG|CTLFLAG_RD,
@ -205,6 +207,44 @@ __mac_execve(td, uap)
#endif
}
static int
kern_execve(td, fname, argv, envv, mac_p)
struct thread *td;
char *fname;
char **argv;
char **envv;
struct mac *mac_p;
{
struct proc *p = td->td_proc;
int error;
if (p->p_flag & P_HADTHREADS) {
PROC_LOCK(p);
if (thread_single(SINGLE_BOUNDARY)) {
PROC_UNLOCK(p);
return (ERESTART); /* Try again later. */
}
PROC_UNLOCK(p);
}
error = do_execve(td, fname, argv, envv, mac_p);
if (p->p_flag & P_HADTHREADS) {
PROC_LOCK(p);
/*
* If success, we upgrade to SINGLE_EXIT state to
* force other threads to suicide.
*/
if (error == 0)
thread_single(SINGLE_EXIT);
else
thread_single_end();
PROC_UNLOCK(p);
}
return (error);
}
/*
* In-kernel implementation of execve(). All arguments are assumed to be
* userspace pointers from the passed thread.
@ -212,7 +252,7 @@ __mac_execve(td, uap)
* MPSAFE
*/
static int
kern_execve(td, fname, argv, envv, mac_p)
do_execve(td, fname, argv, envv, mac_p)
struct thread *td;
char *fname;
char **argv;
@ -254,16 +294,6 @@ kern_execve(td, fname, argv, envv, mac_p)
PROC_LOCK(p);
KASSERT((p->p_flag & P_INEXEC) == 0,
("%s(): process already has P_INEXEC flag", __func__));
if (p->p_flag & P_HADTHREADS) {
if (thread_single(SINGLE_EXIT)) {
PROC_UNLOCK(p);
return (ERESTART); /* Try again later. */
}
/*
* If we get here all other threads are dead,
* and threading mode has been turned off
*/
}
p->p_flag |= P_INEXEC;
PROC_UNLOCK(p);
@ -624,9 +654,13 @@ kern_execve(td, fname, argv, envv, mac_p)
/*
* If tracing the process, trap to debugger so breakpoints
* can be set before the program executes.
* Use tdsignal to deliver signal to current thread, use
* psignal may cause the signal to be delivered to wrong thread
* because that thread will exit, remember we are going to enter
* single thread mode.
*/
if (p->p_flag & P_TRACED)
psignal(p, SIGTRAP);
tdsignal(td, SIGTRAP, SIGTARGET_TD);
/* clear "fork but no exec" flag, as we _are_ execing */
p->p_acflag &= ~AFORK;

83
sys/kern/kern_thread.c
View File

@ -764,7 +764,7 @@ thread_unlink(struct thread *td)
* any sleeping threads that are interruptable. (PCATCH).
*/
int
thread_single(int force_exit)
thread_single(int mode)
{
struct thread *td;
struct thread *td2;
@ -781,36 +781,53 @@ thread_single(int force_exit)
return (0);
/* Is someone already single threading? */
if (p->p_singlethread)
if (p->p_singlethread != NULL && p->p_singlethread != td)
return (1);
if (mode == SINGLE_EXIT) {
p->p_flag |= P_SINGLE_EXIT;
p->p_flag &= ~P_SINGLE_BOUNDARY;
} else {
p->p_flag &= ~P_SINGLE_EXIT;
if (mode == SINGLE_BOUNDARY)
p->p_flag |= P_SINGLE_BOUNDARY;
else
p->p_flag &= ~P_SINGLE_BOUNDARY;
}
p->p_flag |= P_STOPPED_SINGLE;
mtx_lock_spin(&sched_lock);
p->p_singlethread = td;
if (force_exit == SINGLE_EXIT) {
if (mode == SINGLE_EXIT)
remaining = p->p_numthreads;
p->p_flag |= P_SINGLE_EXIT;
} else {
else if (mode == SINGLE_BOUNDARY)
remaining = p->p_numthreads - p->p_boundary_count;
else
remaining = p->p_numthreads - p->p_suspcount;
p->p_flag &= ~P_SINGLE_EXIT;
}
while (remaining != 1) {
FOREACH_THREAD_IN_PROC(p, td2) {
if (td2 == td)
continue;
td2->td_flags |= TDF_ASTPENDING;
if (TD_IS_INHIBITED(td2)) {
if (force_exit == SINGLE_EXIT) {
switch (mode) {
case SINGLE_EXIT:
if (td->td_flags & TDF_DBSUSPEND)
td->td_flags &= ~TDF_DBSUSPEND;
if (TD_IS_SUSPENDED(td2)) {
if (TD_IS_SUSPENDED(td2))
thread_unsuspend_one(td2);
}
if (TD_ON_SLEEPQ(td2) &&
(td2->td_flags & TDF_SINTR)) {
(td2->td_flags & TDF_SINTR))
sleepq_abort(td2);
}
} else {
break;
case SINGLE_BOUNDARY:
if (TD_IS_SUSPENDED(td2) &&
!(td2->td_flags & TDF_BOUNDARY))
thread_unsuspend_one(td2);
if (TD_ON_SLEEPQ(td2) &&
(td2->td_flags & TDF_SINTR))
sleepq_abort(td2);
break;
default:
if (TD_IS_SUSPENDED(td2))
continue;
/*
@ -821,11 +838,14 @@ thread_single(int force_exit)
if (td2->td_inhibitors &
(TDI_SLEEPING | TDI_SWAPPED))
thread_suspend_one(td2);
break;
}
}
}
if (force_exit == SINGLE_EXIT)
if (mode == SINGLE_EXIT)
remaining = p->p_numthreads;
else if (mode == SINGLE_BOUNDARY)
remaining = p->p_numthreads - p->p_boundary_count;
else
remaining = p->p_numthreads - p->p_suspcount;
@ -845,12 +865,14 @@ thread_single(int force_exit)
mtx_unlock_spin(&sched_lock);
PROC_LOCK(p);
mtx_lock_spin(&sched_lock);
if (force_exit == SINGLE_EXIT)
if (mode == SINGLE_EXIT)
remaining = p->p_numthreads;
else if (mode == SINGLE_BOUNDARY)
remaining = p->p_numthreads - p->p_boundary_count;
else
remaining = p->p_numthreads - p->p_suspcount;
}
if (force_exit == SINGLE_EXIT) {
if (mode == SINGLE_EXIT) {
/*
* We have gotten rid of all the other threads and we
* are about to either exit or exec. In either case,
@ -925,6 +947,11 @@ thread_suspend_check(int return_instead)
if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
return (1);
/* Should we goto user boundary if we didn't come from there? */
if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
(p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
return (1);
mtx_lock_spin(&sched_lock);
thread_stopped(p);
/*
@ -932,9 +959,8 @@ thread_suspend_check(int return_instead)
* this thread should just suicide.
* Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
*/
if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td))
thread_exit();
}
/*
* When a thread suspends, it just
@ -942,13 +968,20 @@ thread_suspend_check(int return_instead)
* and stays there.
*/
thread_suspend_one(td);
if (return_instead == 0) {
p->p_boundary_count++;
td->td_flags |= TDF_BOUNDARY;
}
if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
if (p->p_numthreads == p->p_suspcount) {
if (p->p_numthreads == p->p_suspcount)
thread_unsuspend_one(p->p_singlethread);
}
}
PROC_UNLOCK(p);
mi_switch(SW_INVOL, NULL);
if (return_instead == 0) {
p->p_boundary_count--;
td->td_flags &= ~TDF_BOUNDARY;
}
mtx_unlock_spin(&sched_lock);
PROC_LOCK(p);
}
@ -1026,7 +1059,7 @@ thread_single_end(void)
td = curthread;
p = td->td_proc;
PROC_LOCK_ASSERT(p, MA_OWNED);
p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
mtx_lock_spin(&sched_lock);
p->p_singlethread = NULL;
/*
@ -1055,8 +1088,12 @@ thread_sleep_check(struct thread *td)
p = td->td_proc;
mtx_assert(&sched_lock, MA_OWNED);
if (p->p_flag & P_HADTHREADS) {
if ((p->p_flag & P_SINGLE_EXIT) && p->p_singlethread != td)
return (EINTR);
if (p->p_singlethread != td) {
if (p->p_flag & P_SINGLE_EXIT)
return (EINTR);
if (p->p_flag & P_SINGLE_BOUNDARY)
return (ERESTART);
}
if (td->td_flags & TDF_INTERRUPT)
return (td->td_intrval);
}

8
sys/sys/proc.h
View File

@ -336,7 +336,7 @@ struct thread {
#define TDF_UNUSED7 0x00000080 /* --available -- */
#define TDF_TSNOBLOCK 0x00000100 /* Don't block on a turnstile due to race. */
#define TDF_UNUSED9 0x00000200 /* --available -- */
#define TDF_UNUSED10 0x00000400 /* --available -- */
#define TDF_BOUNDARY 0x00000400 /* Thread suspended at user boundary */
#define TDF_ASTPENDING 0x00000800 /* Thread has some asynchronous events. */
#define TDF_TIMOFAIL 0x00001000 /* Timeout from sleep after we were awake. */
#define TDF_INTERRUPT 0x00002000 /* Thread is marked as interrupted. */
@ -573,6 +573,7 @@ struct proc {
struct thread *p_singlethread;/* (c + j) If single threading this is it */
int p_suspcount; /* (c) Num threads in suspended mode. */
struct thread *p_xthread; /* (c) Trap thread */
int p_boundary_count;/* (c) Num threads at user boundary */
/* End area that is zeroed on creation. */
#define p_endzero p_magic
@ -633,7 +634,7 @@ struct proc {
#define P_STOPPED_SINGLE 0x80000 /* Only 1 thread can continue (not to user). */
#define P_PROTECTED 0x100000 /* Do not kill on memory overcommit. */
#define P_SIGEVENT 0x200000 /* Process pending signals changed. */
#define P_SINGLE_BOUNDARY 0x400000 /* Threads should suspend at user boundary. */
#define P_JAILED 0x1000000 /* Process is in jail. */
#define P_INEXEC 0x4000000 /* Process is in execve(). */
@ -681,8 +682,9 @@ struct proc {
/* How values for thread_single(). */
#define SINGLE_NO_EXIT 0
#define SINGLE_EXIT 1
#define SINGLE_BOUNDARY 2
/* XXXKSE: Missing values for thread_signal_check(). */
/* XXXKSE: Missing values for thread_suspsend_check(). */
#ifdef MALLOC_DECLARE
MALLOC_DECLARE(M_PARGS);