Date: Mon, 14 Apr 2008 15:31:37 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: Chagin Dmitry <chagin.dmitry@gmail.com> Cc: freebsd-emulation@freebsd.org Subject: Re: Call for review && test: linux_kdump-1.6 Message-ID: <20080414123137.GH18958@deviant.kiev.zoral.com.ua> In-Reply-To: <20080413234359.H1165@ora.chd.net> References: <20080412181712.Y38920@ora.chd.net> <20080412145401.GA4139@freebsd.org> <20080413214624.S7426@ora.chd.net> <20080413183248.GA68642@freebsd.org> <20080413183659.GA18958@deviant.kiev.zoral.com.ua> <20080413231135.K1079@ora.chd.net> <20080413192614.GC18958@deviant.kiev.zoral.com.ua> <20080413234359.H1165@ora.chd.net>
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On Mon, Apr 14, 2008 at 12:42:29AM +0400, Chagin Dmitry wrote:
> On Sun, 13 Apr 2008, Kostik Belousov wrote:
>=20
> >On Sun, Apr 13, 2008 at 11:11:55PM +0400, Chagin Dmitry wrote:
> >>On Sun, 13 Apr 2008, Kostik Belousov wrote:
> >>
> >>>On Sun, Apr 13, 2008 at 08:32:48PM +0200, Roman Divacky wrote:
> >>>>On Sun, Apr 13, 2008 at 09:58:08PM +0400, Chagin Dmitry wrote:
> >>>>>On Sat, 12 Apr 2008, Roman Divacky wrote:
> >>>>>
> >>>>>>>And question: whether i can add to linuxolator some ktr_struct
> >>>>>>> functionality?
> >>>>>>
> >>>>>>sure... please provide a patch and I'll take care about it.
> >>>>>
> >>>>>ok, thnx :)
> >>>>>what about EJUSTRETURN?
> >>>>>i attached simple patch for demo only (not tested).
> >>>>
> >>>>uh... can you provide diff -u ? I dont understand the diff at all ;)
> >>>
> >>>Also, please note that the ML software strips your attachments. Either
> >>>inline the patch, or use the plain-text content-type for it.
> >>>
> >>
> >>ups... ah google ))
> >>i have understood, sorry and thnx.
> >>Speech about that in linux_kdump it is impossible to distinguish
> >>EJUSTRETURN from a real error. look:
> >>
> >>--- sys/i386/i386/trap.c.orig 2008-04-13 21:39:18.000000000 +0400
> >>+++ sys/i386/i386/trap.c 2008-04-13 22:35:25.000000000 +0400
> >>@@ -1091,8 +1091,12 @@
> >> td->td_proc->p_pid, td->td_name, code);
> >>
> >> #ifdef KTRACE
> >>- if (KTRPOINT(td, KTR_SYSRET))
> >>- ktrsysret(code, error, td->td_retval[0]);
> >>+ if (KTRPOINT(td, KTR_SYSRET)) {
> >>+ if (error =3D=3D EJUSTRETURN)
> >>+ ktrsysret(code, 0, td->td_retval[0]);
> >>+ else
> >>+ ktrsysret(code, error, td->td_retval[0]);
> >>+ }
> >> #endif
> >>
> >> /*
> >>@@ -1104,4 +1108,3 @@
> >>
> >> PTRACESTOP_SC(p, td, S_PT_SCX);
> >> }
> >>-
> >
> >I do not quite understand the intent of this change.
> >
> >EJUSTRETURN is used for two different purposes in the kernel.
> >1. The sigreturn family of the syscalls use it after the interrupted
> >frame is restored to avoid the normal syscall return sequence to modify
> >the machine state.
> >2. It is used by the kernel to notify the in-kernel caller code about
> >some special condition, that nonetheless shall not be returned to the
> >userspace.
> >
> >Only the first case is applicable to the kdump, and IMHO you actually
> >destroy some information, since error =3D=3D EJUSTRETURN is reported as =
0.
> >
> >Could you, please, provide some more arguments in the support of your
> >proposed change ?
> >
>=20
> Thanks for you informative reply Kostya.
> The problem arises only in linux_kdump. Because linux error
> codes negative and EJUSTRETURN coincides with ENOENT.
> Before a call ktr_sysret we decode return codes of emulators syscalls.
Ah, I see. Then, we shall never dump the ERESTART and EJUSTRETURN
for the emulated ABIs. At least, this is true for Linux, I am not
so sure about iBCS2 and SVR4.
Could you test the patch below, instead ?
diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c
index b6a454d..9ccbd4b 100644
--- a/sys/amd64/amd64/trap.c
+++ b/sys/amd64/amd64/trap.c
@@ -912,8 +912,23 @@ syscall(struct trapframe *frame)
td->td_proc->p_pid, td->td_name, code);
=20
#ifdef KTRACE
- if (KTRPOINT(td, KTR_SYSRET))
- ktrsysret(code, error, td->td_retval[0]);
+ if (KTRPOINT(td, KTR_SYSRET)) {
+ int error1;
+
+ /*
+ * The ABIs that use the negative error codes, like
+ * Linux, would confuse the in-kernel errno values
+ * with proper userspace errno. Clean these values to
+ * avoid a confusion in the kdump.
+ */
+ if (p->p_sysent->sv_errsize &&
+ (error =3D=3D EJUSTRETURN || error =3D=3D ERESTART))
+ error1 =3D 0;
+ else
+ error1 =3D error;
+
+ ktrsysret(code, error1, td->td_retval[0]);
+ }
#endif
=20
/*
diff --git a/sys/i386/i386/trap.c b/sys/i386/i386/trap.c
index e7de579..55642d1 100644
--- a/sys/i386/i386/trap.c
+++ b/sys/i386/i386/trap.c
@@ -1091,8 +1091,22 @@ syscall(struct trapframe *frame)
td->td_proc->p_pid, td->td_name, code);
=20
#ifdef KTRACE
- if (KTRPOINT(td, KTR_SYSRET))
- ktrsysret(code, error, td->td_retval[0]);
+ if (KTRPOINT(td, KTR_SYSRET)) {
+ int error1;
+
+ /*
+ * The ABIs that use the negative error codes, like
+ * Linux, would confuse the in-kernel errno values
+ * with proper userspace errno. Clean these values to
+ * avoid a confusion in the kdump.
+ */
+ if (p->p_sysent->sv_errsize &&
+ (error =3D=3D EJUSTRETURN || error =3D=3D ERESTART))
+ error1 =3D 0;
+ else
+ error1 =3D error;
+ ktrsysret(code, error1, td->td_retval[0]);
+ }
#endif
=20
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