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Message-ID: <1315242384.1888.64.camel@dhcp-25-63.brq.redhat.com>
Date: Mon, 05 Sep 2011 19:06:22 +0200
From: Denys Vlasenko <dvlasenk@...hat.com>
To: Denys Vlasenko <vda.linux@...glemail.com>
Cc: Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] Add new PTRACE_O_TRACESTOP option, make it control new
ptrace behavior.
On Mon, 2011-09-05 at 18:51 +0200, Denys Vlasenko wrote:
> > A crude patch is below. It rolls points 1-4 from above into a single
> > new option, PTRACE_O_TRACESTOP.
>
> For easier review, split it into two parts. Part 1 follows.
> (It is still not even compile-tested).
Part 2. (ignore untitled one sent a few mins ago)
--
vda
Add new PTRACE_O_TRACESTOP option, make it control new ptrace behavior.
Introduce new ptrace option, PTRACE_O_TRACESTOP. This makes API
more symmetric: every PTRACE_EVENT_event has corresponding PTRACE_O_TRACEevent now,
as it used to have before PTRACE_SEIZE was introduced.
PTRACE_SEIZE does not assume PTRACE_O_TRACESTOP, but with this patch
it allows any PTRACE_O_opts to be set at attach time (they are passed in data param)
- including PTRACE_O_TRACESTOP, of course. Without any options,
PTRACE_SEIZE is equivalent to PTRACE_ATTACH. With only PTRACE_O_TRACESTOP option,
PTRACE_SEIZE behavior will be the same as PTRACE_SEIZE behavior before this patch.
This opens up two new possibilities:
(1) Ptrace options can be set on attach. Can be used to close a few corner cases
in strace where we get unwanted behavior before we have a chance to set options,
and removes the need to track "did we set opts for this task" state in strace
internals.
(2) PTRACE_LISTEN, PTRACE_INTERRUPT commands and PTRACE_EVENT_STOP event
can be enabled with PTRACE_SETOPTIONS with PTRACE_O_TRACESTOP.
Not a big deal, but IMO this makes API more symmetric.
All formerly PTRACE_SEIZE-enabled behavior is now enabled by
PTRACE_O_TRACESTOP instead (by PT_TRACE_STOP bit). PT_SEIZED bit is removed.
Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 9aa669c..e2ba2dd 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -62,8 +62,9 @@
#define PTRACE_O_TRACEEXEC 0x00000010
#define PTRACE_O_TRACEVFORKDONE 0x00000020
#define PTRACE_O_TRACEEXIT 0x00000040
+#define PTRACE_O_TRACESTOP 0x00000080
-#define PTRACE_O_MASK 0x0000007f
+#define PTRACE_O_MASK 0x000000ff
/* Wait extended result codes for the above trace options. */
#define PTRACE_EVENT_FORK 1
@@ -85,7 +86,6 @@
* flags. When the a task is stopped the ptracer owns task->ptrace.
*/
-#define PT_SEIZED 0x00010000 /* SEIZE used, enable new behavior */
#define PT_PTRACED 0x00000001
#define PT_DTRACE 0x00000002 /* delayed trace (used on m68k, i386) */
#define PT_PTRACE_CAP 0x00000004 /* ptracer can follow suid-exec */
@@ -100,6 +100,7 @@
#define PT_TRACE_EXEC PT_EVENT_FLAG(PTRACE_EVENT_EXEC)
#define PT_TRACE_VFORK_DONE PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE)
#define PT_TRACE_EXIT PT_EVENT_FLAG(PTRACE_EVENT_EXIT)
+#define PT_TRACE_STOP PT_EVENT_FLAG(PTRACE_EVENT_STOP)
/* single stepping state bits (used on ARM and PA-RISC) */
#define PT_SINGLESTEP_BIT 31
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 9c3536d..0bf3d74 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -267,9 +267,7 @@ static int ptrace_attach(struct task_struct *task, long request,
if (task->ptrace)
goto unlock_tasklist;
- task->ptrace = PT_PTRACED;
- if (seize)
- task->ptrace |= PT_SEIZED;
+ task->ptrace = PT_PTRACED | (flags << PT_OPT_FLAG_SHIFT);
if (task_ns_capable(task, CAP_SYS_PTRACE))
task->ptrace |= PT_PTRACE_CAP;
@@ -653,7 +651,7 @@ static int ptrace_regset(struct task_struct *task, int req, unsigned int type,
int ptrace_request(struct task_struct *child, long request,
unsigned long addr, unsigned long data)
{
- bool seized = child->ptrace & PT_SEIZED;
+ bool stop_events_enabled = child->ptrace & PT_TRACE_STOP;
int ret = -EIO;
siginfo_t siginfo, *si;
void __user *datavp = (void __user *) data;
@@ -702,7 +700,7 @@ int ptrace_request(struct task_struct *child, long request,
* The actual trap might not be PTRACE_EVENT_STOP trap but
* the pending condition is cleared regardless.
*/
- if (unlikely(!seized || !lock_task_sighand(child, &flags)))
+ if (unlikely(!stop_events_enabled || !lock_task_sighand(child, &flags)))
break;
/*
@@ -727,7 +725,7 @@ int ptrace_request(struct task_struct *child, long request,
* again. Alternatively, ptracer can issue INTERRUPT to
* finish listening and re-trap tracee into STOP.
*/
- if (unlikely(!seized || !lock_task_sighand(child, &flags)))
+ if (unlikely(!stop_events_enabled || !lock_task_sighand(child, &flags)))
break;
si = child->last_siginfo;
diff --git a/kernel/signal.c b/kernel/signal.c
index 291c970..9248600 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -823,8 +823,8 @@ static int check_kill_permission(int sig, struct siginfo *info,
* @t: tracee wanting to notify tracer
*
* This function schedules sticky ptrace trap which is cleared on the next
- * TRAP_STOP to notify ptracer of an event. @t must have been seized by
- * ptracer.
+ * TRAP_STOP to notify ptracer of an event. @t must have PTRACE_O_TRACESTOP
+ * option active.
*
* If @t is running, STOP trap will be taken. If trapped for STOP and
* ptracer is listening for events, tracee is woken up so that it can
@@ -837,7 +837,7 @@ static int check_kill_permission(int sig, struct siginfo *info,
*/
static void ptrace_trap_notify(struct task_struct *t)
{
- WARN_ON_ONCE(!(t->ptrace & PT_SEIZED));
+ WARN_ON_ONCE(!(t->ptrace & PT_TRACE_STOP));
assert_spin_locked(&t->sighand->siglock);
task_set_jobctl_pending(t, JOBCTL_TRAP_NOTIFY);
@@ -882,7 +882,7 @@ static int prepare_signal(int sig, struct task_struct *p, int from_ancestor_ns)
do {
task_clear_jobctl_pending(t, JOBCTL_STOP_PENDING);
rm_from_queue(SIG_KERNEL_STOP_MASK, &t->pending);
- if (likely(!(t->ptrace & PT_SEIZED)))
+ if (likely(!(t->ptrace & PT_TRACE_STOP)))
wake_up_state(t, __TASK_STOPPED);
else
ptrace_trap_notify(t);
@@ -2004,7 +2004,7 @@ static bool do_signal_stop(int signr)
if (!task_is_stopped(t) &&
task_set_jobctl_pending(t, signr | gstop)) {
sig->group_stop_count++;
- if (likely(!(t->ptrace & PT_SEIZED)))
+ if (likely(!(t->ptrace & PT_TRACE_STOP)))
signal_wake_up(t, 0);
else
ptrace_trap_notify(t);
@@ -2057,13 +2057,13 @@ static bool do_signal_stop(int signr)
/**
* do_jobctl_trap - take care of ptrace jobctl traps
*
- * When PT_SEIZED, it's used for both group stop and explicit
- * SEIZE/INTERRUPT traps. Both generate PTRACE_EVENT_STOP trap with
+ * When PT_TRACE_STOP is on, it's used for both group stop and explicit
+ * INTERRUPT traps. Both generate PTRACE_EVENT_STOP trap with
* accompanying siginfo. If stopped, lower eight bits of exit_code contain
* the stop signal; otherwise, %SIGTRAP.
*
- * When !PT_SEIZED, it's used only for group stop trap with stop signal
- * number as exit_code and no siginfo.
+ * When PT_TRACE_STOP is off, it's used only for group stop trap
+ * with stop signal number as exit_code and no siginfo.
*
* CONTEXT:
* Must be called with @current->sighand->siglock held, which may be
@@ -2074,7 +2074,7 @@ static void do_jobctl_trap(void)
struct signal_struct *signal = current->signal;
int signr = current->jobctl & JOBCTL_STOP_SIGMASK;
- if (current->ptrace & PT_SEIZED) {
+ if (current->ptrace & PT_TRACE_STOP) {
if (!signal->group_stop_count &&
!(signal->flags & SIGNAL_STOP_STOPPED))
signr = SIGTRAP;
--
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