[patch 0/3] add rt_tgsigqueueinfo syscall -V2

[patch 0/3] add rt_tgsigqueueinfo syscall -V2

[Thomas Gleixner]

sys_kill has a counterpart sys_tgkill which allows to send signals to
a particular thread. sys_rt_sigqueueinfo is lacking such a counterpart.

Aside of the asymetry it is a show stopper for migrating applications
from other unix-alike RTOSes.

The following patch series implements rt_tgsigqueueinfo and hooks it
up for x86.

Changes since V1:
    - match rt_siqqueueinfo and rt_tgsigqueueinfo handling of 
      info.si_pid/si_uid


Find below the raw documentation.

Thanks,

        tglx
----

NAME
       rt_tgsigqueueinfo - Send signal information to a signal to a thread

SYNOPSIS
       long sys_rt_tgsigqueueinfo (int tgid, int tid, int sig, siginfo_t *uinfo);

DESCRIPTION

       rt_tgsigqueueinfo sends signal sig information uinfo to the
       thread with the thread ID tid in the thread group tgid.  (By
       contrast, rt_sigqueueinfo(2) can only be used to send a signal
       info to a process (i.e., thread group) as a whole, and the
       signal will be delivered to an arbitrary thread within that
       process.)

RETURN VALUE

       rt_tgsigqueueinfo returns 0 on success; otherwise,
       rt_sigqueueinfo returns one of the errors listed in the
       "Errors" section.

ERRORS
       -EFAULT
              An invalid value for uinfo was specified.

       -EINVAL
              An invalid TID, TGID or signal was specified.

       -EPERM
              Permission denied.  For the required permissions,
              see rt_sigqueueinfo(2).

       -ESRCH
              No process with the specified thread ID and thread group
              ID exists. 

[patch 1/3] signals: split do_tkill

[Thomas Gleixner]

[-- Attachment #1: signals-split-do-tkill.patch --]
[-- Type: text/plain, Size: 2061 bytes --]

Split out the code from do_tkill to make it reusable by the follow up
patch which implements sys_rt_tgsigqueueinfo

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/signal.c |   30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

Index: linux-2.6/kernel/signal.c
===================================================================
--- linux-2.6.orig/kernel/signal.c
+++ linux-2.6/kernel/signal.c
@@ -2235,24 +2235,17 @@ SYSCALL_DEFINE2(kill, pid_t, pid, int, s
 	return kill_something_info(sig, &info, pid);
 }
 
-static int do_tkill(pid_t tgid, pid_t pid, int sig)
+static int
+do_send_specific(pid_t tgid, pid_t pid, int sig, struct siginfo *info)
 {
-	int error;
-	struct siginfo info;
 	struct task_struct *p;
 	unsigned long flags;
-
-	error = -ESRCH;
-	info.si_signo = sig;
-	info.si_errno = 0;
-	info.si_code = SI_TKILL;
-	info.si_pid = task_tgid_vnr(current);
-	info.si_uid = current_uid();
+	int error = -ESRCH;
 
 	rcu_read_lock();
 	p = find_task_by_vpid(pid);
 	if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) {
-		error = check_kill_permission(sig, &info, p);
+		error = check_kill_permission(sig, info, p);
 		/*
 		 * The null signal is a permissions and process existence
 		 * probe.  No signal is actually delivered.
@@ -2262,7 +2255,7 @@ static int do_tkill(pid_t tgid, pid_t pi
 		 * signal is private anyway.
 		 */
 		if (!error && sig && lock_task_sighand(p, &flags)) {
-			error = specific_send_sig_info(sig, &info, p);
+			error = specific_send_sig_info(sig, info, p);
 			unlock_task_sighand(p, &flags);
 		}
 	}
@@ -2271,6 +2264,19 @@ static int do_tkill(pid_t tgid, pid_t pi
 	return error;
 }
 
+static int do_tkill(pid_t tgid, pid_t pid, int sig)
+{
+	struct siginfo info;
+
+	info.si_signo = sig;
+	info.si_errno = 0;
+	info.si_code = SI_TKILL;
+	info.si_pid = task_tgid_vnr(current);
+	info.si_uid = current_uid();
+
+	return do_send_specific(tgid, pid, sig, &info);
+}
+
 /**
  *  sys_tgkill - send signal to one specific thread
  *  @tgid: the thread group ID of the thread

[patch 2/3] signals: implement sys_rt_tgsigqueueinfo

[Thomas Gleixner]

[-- Attachment #1: signals-implement-rt-tgsigqueueinfo.patch --]
[-- Type: text/plain, Size: 3582 bytes --]

sys_kill has the per thread counterpart sys_tgkill. sigqueueinfo is
missing a thread directed counterpart. Such an interface is important
for migrating applications from other OSes which have the per thread
delivery implemented.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/compat.h |    2 ++
 include/linux/signal.h |    2 ++
 kernel/compat.c        |   11 +++++++++++
 kernel/signal.c        |   26 ++++++++++++++++++++++++++
 4 files changed, 41 insertions(+)

Index: linux-2.6/include/linux/compat.h
===================================================================
--- linux-2.6.orig/include/linux/compat.h
+++ linux-2.6/include/linux/compat.h
@@ -208,6 +208,8 @@ int copy_siginfo_from_user32(siginfo_t *
 int copy_siginfo_to_user32(struct compat_siginfo __user *to, siginfo_t *from);
 int get_compat_sigevent(struct sigevent *event,
 		const struct compat_sigevent __user *u_event);
+long compat_sys_rt_tgsigqueueinfo(compat_pid_t tgid, compat_pid_t pid, int sig,
+				  struct compat_siginfo __user *uinfo);
 
 static inline int compat_timeval_compare(struct compat_timeval *lhs,
 					struct compat_timeval *rhs)
Index: linux-2.6/include/linux/signal.h
===================================================================
--- linux-2.6.orig/include/linux/signal.h
+++ linux-2.6/include/linux/signal.h
@@ -235,6 +235,8 @@ static inline int valid_signal(unsigned 
 extern int next_signal(struct sigpending *pending, sigset_t *mask);
 extern int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p);
 extern int __group_send_sig_info(int, struct siginfo *, struct task_struct *);
+extern long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig,
+				 siginfo_t *info);
 extern long do_sigpending(void __user *, unsigned long);
 extern int sigprocmask(int, sigset_t *, sigset_t *);
 extern int show_unhandled_signals;
Index: linux-2.6/kernel/compat.c
===================================================================
--- linux-2.6.orig/kernel/compat.c
+++ linux-2.6/kernel/compat.c
@@ -882,6 +882,17 @@ compat_sys_rt_sigtimedwait (compat_sigse
 
 }
 
+asmlinkage long
+compat_sys_rt_tgsigqueueinfo(compat_pid_t tgid, compat_pid_t pid, int sig,
+			     struct compat_siginfo __user *uinfo)
+{
+	siginfo_t info;
+
+	if (copy_siginfo_from_user32(&info, uinfo))
+		return -EFAULT;
+	return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
+}
+
 #ifdef __ARCH_WANT_COMPAT_SYS_TIME
 
 /* compat_time_t is a 32 bit "long" and needs to get converted. */
Index: linux-2.6/kernel/signal.c
===================================================================
--- linux-2.6.orig/kernel/signal.c
+++ linux-2.6/kernel/signal.c
@@ -2326,6 +2326,32 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, 
 	return kill_proc_info(sig, &info, pid);
 }
 
+long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
+{
+	/* This is only valid for single tasks */
+	if (pid <= 0 || tgid <= 0)
+		return -EINVAL;
+
+	/* Not even root can pretend to send signals from the kernel.
+	   Nor can they impersonate a kill(), which adds source info.  */
+	if (info->si_code >= 0)
+		return -EPERM;
+	info->si_signo = sig;
+
+	return do_send_specific(tgid, pid, sig, info);
+}
+
+SYSCALL_DEFINE4(rt_tgsigqueueinfo, pid_t, tgid, pid_t, pid, int, sig,
+		siginfo_t __user *, uinfo)
+{
+	siginfo_t info;
+
+	if (copy_from_user(&info, uinfo, sizeof(siginfo_t)))
+		return -EFAULT;
+
+	return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
+}
+
 int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
 {
 	struct task_struct *t = current;

[patch 3/3] x86: hookup sys_rt_tgsigqueueinfo

[Thomas Gleixner]

[-- Attachment #1: x86-hookup-rt-tgsigqueueinfo.patch --]
[-- Type: text/plain, Size: 1994 bytes --]

Make the new sys_rt_tgsigqueueinfo available for x86.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/ia32/ia32entry.S          |    1 +
 arch/x86/include/asm/unistd_32.h   |    1 +
 arch/x86/include/asm/unistd_64.h   |    2 ++
 arch/x86/kernel/syscall_table_32.S |    1 +
 4 files changed, 5 insertions(+)

Index: linux-2.6-tip/arch/x86/ia32/ia32entry.S
===================================================================
--- linux-2.6-tip.orig/arch/x86/ia32/ia32entry.S
+++ linux-2.6-tip/arch/x86/ia32/ia32entry.S
@@ -828,4 +828,5 @@ ia32_sys_call_table:
 	.quad sys_dup3			/* 330 */
 	.quad sys_pipe2
 	.quad sys_inotify_init1
+	.quad compat_sys_rt_tgsigqueueinfo
 ia32_syscall_end:
Index: linux-2.6-tip/arch/x86/include/asm/unistd_32.h
===================================================================
--- linux-2.6-tip.orig/arch/x86/include/asm/unistd_32.h
+++ linux-2.6-tip/arch/x86/include/asm/unistd_32.h
@@ -338,6 +338,7 @@
 #define __NR_dup3		330
 #define __NR_pipe2		331
 #define __NR_inotify_init1	332
+#define __NR_rt_tgsigqueueinfo	333
 
 #ifdef __KERNEL__
 
Index: linux-2.6-tip/arch/x86/include/asm/unistd_64.h
===================================================================
--- linux-2.6-tip.orig/arch/x86/include/asm/unistd_64.h
+++ linux-2.6-tip/arch/x86/include/asm/unistd_64.h
@@ -653,6 +653,8 @@ __SYSCALL(__NR_dup3, sys_dup3)
 __SYSCALL(__NR_pipe2, sys_pipe2)
 #define __NR_inotify_init1			294
 __SYSCALL(__NR_inotify_init1, sys_inotify_init1)
+#define __NR_rt_tgsigqueueinfo			295
+__SYSCALL(__NR_rt_tgsigqueueinfo, sys_rt_tgsigqueueinfo)
 
 
 #ifndef __NO_STUBS
Index: linux-2.6-tip/arch/x86/kernel/syscall_table_32.S
===================================================================
--- linux-2.6-tip.orig/arch/x86/kernel/syscall_table_32.S
+++ linux-2.6-tip/arch/x86/kernel/syscall_table_32.S
@@ -332,3 +332,4 @@ ENTRY(sys_call_table)
 	.long sys_dup3			/* 330 */
 	.long sys_pipe2
 	.long sys_inotify_init1
+	.long sys_rt_tgsigqueueinfo

Re: [patch 0/3] add rt_tgsigqueueinfo syscall -V2

[Oleg Nesterov]

On 03/24, Thomas Gleixner wrote:
>
> sys_kill has a counterpart sys_tgkill which allows to send signals to
> a particular thread. sys_rt_sigqueueinfo is lacking such a counterpart.
>
> Aside of the asymetry it is a show stopper for migrating applications
> from other unix-alike RTOSes.
>
> The following patch series implements rt_tgsigqueueinfo and hooks it
> up for x86.
>
> Changes since V1:
>     - match rt_siqqueueinfo and rt_tgsigqueueinfo handling of
>       info.si_pid/si_uid

I think this all is correct. And I think "Changes since V1" are good,
rt_tgsigqueueinfo() should not play with si_pid/si_uid.

Reviewed-by: Oleg Nesterov <oleg@redhat.com>

Re: [patch 0/3] add rt_tgsigqueueinfo syscall -V2

[Michael Kerrisk]

On Wed, Apr 1, 2009 at 4:26 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> On 03/24, Thomas Gleixner wrote:
>>
>> sys_kill has a counterpart sys_tgkill which allows to send signals to
>> a particular thread. sys_rt_sigqueueinfo is lacking such a counterpart.
>>
>> Aside of the asymetry it is a show stopper for migrating applications
>> from other unix-alike RTOSes.
>>
>> The following patch series implements rt_tgsigqueueinfo and hooks it
>> up for x86.
>>
>> Changes since V1:
>>     - match rt_siqqueueinfo and rt_tgsigqueueinfo handling of
>>       info.si_pid/si_uid
>
> I think this all is correct. And I think "Changes since V1" are good,
> rt_tgsigqueueinfo() should not play with si_pid/si_uid.
>
> Reviewed-by: Oleg Nesterov <oleg@redhat.com>

I had two concerns with earlier iteraions of this patch (
http://thread.gmane.org/gmane.linux.kernel/799866/focus=667 ):

[[
1) With rt_siqueueinfo(), we can get the PID (TGID) of the sender,
which enables the receiver of the signal to know who the sender was,
and perhaps use that information to (for example) send a signal in the
other direction.

With rt_tgsigqueueinfo(), we don't quite have that ability: all that
the receiver gets is the TGID of the sender, not the TID.  This means
that we can't (for example) send a signal back to the precise thread
that signaled us. I'm not sure if this matters or not (but perhaps it
might when sender and receiver are in the same process?).  I'm also
not sure whether we want to do anything about this (i.e., extending
siginfo_t to include a si_tid field), but I wanted to point out this
assymetry w.r.t. to rt_sigqueueinfo(), in case you had not considered
it.

2) With rt_sigqueueinfo(), we can specify the si_pid and and si_uid
fields that should be sent to the receiver.  This is not possible with
rt_tgsigqueueinfo(), which always supplied the caller';s PID and UID
in the si_pid and si_uid fields sent to the receiver.  See the
following, created using my test programs below (the 111 & 222
arguments to t_*sigqueueinfo set the si_pid and si_uid fields in the
siginfo_t given to the *sigqueueinfo() syscall):
]]

Roland pointed out that the first problem could be dealt with via the
sigval associated with the signal.

The second problem is addressed by this change:

>> Changes since V1:
>>     - match rt_siqqueueinfo and rt_tgsigqueueinfo handling of
>>       info.si_pid/si_uid

I've tested this version of the interface (using the programs shown in
the mail thread referred to above), and it works as I expect, and I
find the design otherwise sane, so:

Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Tested-by: Michael Kerrisk <mtk.manpages@gmail.com>

Cheers,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html
Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html

Re: [patch 0/3] add rt_tgsigqueueinfo syscall -V2

[Roland McGrath]

> 1) With rt_siqueueinfo(), we can get the PID (TGID) of the sender,

No.  You can get whatever the caller put into the siginfo_t.
Only the si_signo field is set by the kernel.

> With rt_tgsigqueueinfo(), [...]

You still get whatever the caller put into the siginfo_t.


Thanks,
Roland

Re: [patch 0/3] add rt_tgsigqueueinfo syscall -V2

[Michael Kerrisk]

On Wed, Apr 1, 2009 at 2:25 PM, Roland McGrath <roland@redhat.com> wrote:
>> 1) With rt_siqueueinfo(), we can get the PID (TGID) of the sender,
>
> No.  You can get whatever the caller put into the siginfo_t.
> Only the si_signo field is set by the kernel.
>
>> With rt_tgsigqueueinfo(), [...]
>
> You still get whatever the caller put into the siginfo_t.

Yes.  I wrote the text awkwardly, but I think the point was clear.  In
my point 1, I wrongly thought we needed a way to get the sender's TID
to the receiver, and you pointed out that sigval could do the job.  In
my point 2, I made the same observation as you just made above.

Thanks,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html
Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html