From owner-freebsd-current@FreeBSD.ORG Tue Feb 7 12:10:37 2012 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 01A8C1065680 for ; Tue, 7 Feb 2012 12:10:37 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from mail.zoral.com.ua (mx0.zoral.com.ua [91.193.166.200]) by mx1.freebsd.org (Postfix) with ESMTP id 4EF388FC1B for ; Tue, 7 Feb 2012 12:10:35 +0000 (UTC) Received: from skuns.kiev.zoral.com.ua (localhost [127.0.0.1]) by mail.zoral.com.ua (8.14.2/8.14.2) with ESMTP id q17CANja079856 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Tue, 7 Feb 2012 14:10:23 +0200 (EET) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (kostik@localhost [127.0.0.1]) by deviant.kiev.zoral.com.ua (8.14.5/8.14.5) with ESMTP id q17CANcc040014; Tue, 7 Feb 2012 14:10:23 +0200 (EET) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by deviant.kiev.zoral.com.ua (8.14.5/8.14.5/Submit) id q17CANax040013; Tue, 7 Feb 2012 14:10:23 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: deviant.kiev.zoral.com.ua: kostik set sender to kostikbel@gmail.com using -f Date: Tue, 7 Feb 2012 14:10:22 +0200 From: Konstantin Belousov To: Dmitry Mikulin Message-ID: <20120207121022.GC3283@deviant.kiev.zoral.com.ua> References: <20120125074824.GD2726@deviant.kiev.zoral.com.ua> <4F2094B4.70707@juniper.net> <20120126122326.GT2726@deviant.kiev.zoral.com.ua> <4F22E8FD.6010201@juniper.net> <20120129074843.GL2726@deviant.kiev.zoral.com.ua> <4F26E0D1.8040100@juniper.net> <20120130192727.GZ2726@deviant.kiev.zoral.com.ua> <4F2C756A.80900@juniper.net> <20120204204218.GC3283@deviant.kiev.zoral.com.ua> <4F3043E2.6090607@juniper.net> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="lmWPTIvm4M7zUP/T" Content-Disposition: inline In-Reply-To: <4F3043E2.6090607@juniper.net> User-Agent: Mutt/1.4.2.3i X-Virus-Scanned: clamav-milter 0.95.2 at skuns.kiev.zoral.com.ua X-Virus-Status: Clean X-Spam-Status: No, score=-3.9 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.2.5 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on skuns.kiev.zoral.com.ua Cc: freebsd-current Current , Marcel Moolenaar Subject: Re: [ptrace] please review follow fork/exec changes X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 07 Feb 2012 12:10:37 -0000 --lmWPTIvm4M7zUP/T Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Feb 06, 2012 at 01:19:30PM -0800, Dmitry Mikulin wrote: >=20 > >I see what is going on. The wait loop for P_PPWAIT in do_fork() simply > >do not allow the ptracestop() in the syscall return path to be reached. > >There seems to be more problems. In particular, I do not see anything > >which would prevent the child from being reapped while the loop is > >executing (assume that the parent is multithreaded and other thread > >processed SIGCHLD and called wait). > > > >Lets deal with these bugs after your proposal for interface changes is > >dealt with. >=20 > OK. >=20 > > > >Yes, I agree with the proposal to add flag to the child lwp info. > >I think it will be easier if the flag is different from PL_FLAG_FORKED. > >I named it PL_FLAG_CHILD. > > > >PT_FOLLOW_EXEC is easy to implement, but my question is, how can debugger > >operate (correctly) if it ignores exec events ? After exec, the whole > >cached state of the debuggee must be invalidated, and since debugger > >ignores the notification when the invalidation shall be done, it probably > >gets very confused. >=20 > You're right, the debugger needs to handle exec() events implicitly when = it=20 > starts up executables. The problem is that there is OS-independent=20 > machinery in gdb which handles statup fork-exec sequence differently from= =20 > when the debuggee itself does an exec(). Basically in the event handling= =20 > code I need to be able to distinguish app startup by gdb from an exec don= e=20 > by the app. Other OS-es have flags like PL_FLAG_EXEC set on demand: they= =20 > have an equivalent of PT_FOLLOW_EXEC. I attached a modified patch that=20 > solves the problem. It tries to separate the always-on TDB_EXEC from the= =20 > on-demand TDB_FOLLOWEXEC without changing existing functionality. Let me= =20 > know if it's acceptable. So, do you in fact need to distinguish exec stops from syscall exit against exec stops from PT_FOLLOW_EXEC, or do you need to only get stops at exec returns from PT_CONTINUE when explicitely requested them ? I would prefer to not introduce another PL_FLAG_EXEC with the same semantic as PL_FLAG_EXEC. Instead, would the following patch be fine for your purposes ? With it, stop on exec should only occur if PT_SCX is requested, or PT_CONTINUE and PT_FOLLOW_EXEC. [I am unable to fully test this until tomorrow]. diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c index 135f798..67cb1b2 100644 --- a/sys/kern/kern_exec.c +++ b/sys/kern/kern_exec.c @@ -56,6 +56,7 @@ __FBSDID("$FreeBSD$"); #include #include #include +#include #include #include #include @@ -889,7 +890,9 @@ exec_fail_dealloc: =20 if (error =3D=3D 0) { PROC_LOCK(p); - td->td_dbgflags |=3D TDB_EXEC; + if ((p->p_flag & P_TRACED) !=3D 0 && + ((P_FOLLOWEXEC) !=3D 0 || (p->p_stops & S_PT_SCX) !=3D 0)) + td->td_dbgflags |=3D TDB_EXEC; PROC_UNLOCK(p); =20 /* diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c index 60639c9..e447c93 100644 --- a/sys/kern/kern_fork.c +++ b/sys/kern/kern_fork.c @@ -1035,7 +1035,9 @@ fork_return(struct thread *td, struct trapframe *fram= e) p->p_oppid =3D p->p_pptr->p_pid; proc_reparent(p, dbg); sx_xunlock(&proctree_lock); + td->td_dbgflags |=3D TDB_CHILD; ptracestop(td, SIGSTOP); + td->td_dbgflags &=3D ~TDB_CHILD; } else { /* * ... otherwise clear the request. diff --git a/sys/kern/sys_process.c b/sys/kern/sys_process.c index 4510380..79bbaed 100644 --- a/sys/kern/sys_process.c +++ b/sys/kern/sys_process.c @@ -660,6 +660,7 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void= *addr, int data) case PT_TO_SCX: case PT_SYSCALL: case PT_FOLLOW_FORK: + case PT_FOLLOW_EXEC: case PT_DETACH: sx_xlock(&proctree_lock); proctree_locked =3D 1; @@ -873,6 +874,12 @@ kern_ptrace(struct thread *td, int req, pid_t pid, voi= d *addr, int data) else p->p_flag &=3D ~P_FOLLOWFORK; break; + case PT_FOLLOW_EXEC: + if (data) + p->p_flag |=3D P_FOLLOWEXEC; + else + p->p_flag &=3D ~P_FOLLOWEXEC; + break; =20 case PT_STEP: case PT_CONTINUE: @@ -936,7 +943,8 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void= *addr, int data) p->p_sigparent =3D SIGCHLD; } p->p_oppid =3D 0; - p->p_flag &=3D ~(P_TRACED | P_WAITED | P_FOLLOWFORK); + p->p_flag &=3D ~(P_TRACED | P_WAITED | P_FOLLOWFORK | + P_FOLLOWEXEC); =20 /* should we send SIGCHLD? */ /* childproc_continued(p); */ @@ -1145,6 +1153,8 @@ kern_ptrace(struct thread *td, int req, pid_t pid, vo= id *addr, int data) pl->pl_flags |=3D PL_FLAG_FORKED; pl->pl_child_pid =3D td2->td_dbg_forked; } + if (td2->td_dbgflags & TDB_CHILD) + pl->pl_flags |=3D PL_FLAG_CHILD; pl->pl_sigmask =3D td2->td_sigmask; pl->pl_siglist =3D td2->td_siglist; strcpy(pl->pl_tdname, td2->td_name); diff --git a/sys/sys/proc.h b/sys/sys/proc.h index 9ebfe83..bec7223 100644 --- a/sys/sys/proc.h +++ b/sys/sys/proc.h @@ -384,6 +384,7 @@ do { \ process */ #define TDB_STOPATFORK 0x00000080 /* Stop at the return from fork (child only) */ +#define TDB_CHILD 0x00000100 /* New child indicator for ptrace() */ =20 /* * "Private" flags kept in td_pflags: @@ -613,6 +614,7 @@ struct proc { #define P_HWPMC 0x800000 /* Process is using HWPMCs */ =20 #define P_JAILED 0x1000000 /* Process is in jail. */ +#define P_FOLLOWEXEC 0x2000000 /* Report execs with ptrace. */ #define P_INEXEC 0x4000000 /* Process is in execve(). */ #define P_STATCHILD 0x8000000 /* Child process stopped or exited. */ #define P_INMEM 0x10000000 /* Loaded into memory. */ diff --git a/sys/sys/ptrace.h b/sys/sys/ptrace.h index 2583d59..05c758c 100644 --- a/sys/sys/ptrace.h +++ b/sys/sys/ptrace.h @@ -64,6 +64,7 @@ #define PT_SYSCALL 22 =20 #define PT_FOLLOW_FORK 23 +#define PT_FOLLOW_EXEC 24 =20 #define PT_GETREGS 33 /* get general-purpose registers */ #define PT_SETREGS 34 /* set general-purpose registers */ @@ -106,7 +107,8 @@ struct ptrace_lwpinfo { #define PL_FLAG_SCX 0x08 /* syscall leave point */ #define PL_FLAG_EXEC 0x10 /* exec(2) succeeded */ #define PL_FLAG_SI 0x20 /* siginfo is valid */ -#define PL_FLAG_FORKED 0x40 /* new child */ +#define PL_FLAG_FORKED 0x40 /* child born */ +#define PL_FLAG_CHILD 0x80 /* I am from child */ sigset_t pl_sigmask; /* LWP signal mask */ sigset_t pl_siglist; /* LWP pending signal */ struct __siginfo pl_siginfo; /* siginfo for signal */ --lmWPTIvm4M7zUP/T Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (FreeBSD) iEYEARECAAYFAk8xFK4ACgkQC3+MBN1Mb4gpWwCbB1kzJxlazKuClYS12oyoeggT gz8AoKZMLnE/W9E/eIzEzGJK7kP7I9fu =EncL -----END PGP SIGNATURE----- --lmWPTIvm4M7zUP/T--