Messages in this thread | | | Subject | Re: [PATCH 08/17] ptrace/m68k: Stop open coding ptrace_report_syscall | From | Michael Schmitz <> | Date | Tue, 11 Jan 2022 14:33:50 +1300 |
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Hi Geert,
Am 11.01.2022 um 06:54 schrieb Geert Uytterhoeven: > Hi Al, > > CC Michael/m68k, > > On Mon, Jan 10, 2022 at 5:20 PM Al Viro <viro@zeniv.linux.org.uk> wrote: >> On Mon, Jan 10, 2022 at 04:26:57PM +0100, Geert Uytterhoeven wrote: >>> On Mon, Jan 3, 2022 at 10:33 PM Eric W. Biederman <ebiederm@xmission.com> wrote: >>>> The generic function ptrace_report_syscall does a little more >>>> than syscall_trace on m68k. The function ptrace_report_syscall >>>> stops early if PT_TRACED is not set, it sets ptrace_message, >>>> and returns the result of fatal_signal_pending. >>>> >>>> Setting ptrace_message to a passed in value of 0 is effectively not >>>> setting ptrace_message, making that additional work a noop. >>>> >>>> Returning the result of fatal_signal_pending and letting the caller >>>> ignore the result becomes a noop in this change. >>>> >>>> When a process is ptraced, the flag PT_PTRACED is always set in >>>> current->ptrace. Testing for PT_PTRACED in ptrace_report_syscall is >>>> just an optimization to fail early if the process is not ptraced. >>>> Later on in ptrace_notify, ptrace_stop will test current->ptrace under >>>> tasklist_lock and skip performing any work if the task is not ptraced. >>>> >>>> Cc: Geert Uytterhoeven <geert@linux-m68k.org> >>>> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> >>> >>> As this depends on the removal of a parameter from >>> ptrace_report_syscall() earlier in this series: >>> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> >> >> FWIW, I would suggest taking it a bit further: make syscall_trace_enter() >> and syscall_trace_leave() in m68k ptrace.c unconditional, replace the >> calls of syscall_trace() in entry.S with syscall_trace_enter() and >> syscall_trace_leave() resp. and remove syscall_trace(). >> >> Geert, do you see any problems with that? The only difference is that >> current->ptrace_message would be set to 1 for ptrace stop on entry and >> 2 - on leave. Currently m68k just has it 0 all along. >> >> It is user-visible (the whole point is to let the tracer see which >> stop it is - entry or exit one), so somebody using PTRACE_GETEVENTMSG >> on syscall stops would start seeing 1 or 2 instead of "0 all along". >> That's how it works on all other architectures (including m68k-nommu), >> and I doubt that anything in userland will get broken. >> >> Behaviour of PTRACE_GETEVENTMSG for other stops (fork, etc.) remains >> as-is, of course. > > In fact Michael did so in "[PATCH v7 1/2] m68k/kernel - wire up > syscall_trace_enter/leave for m68k"[1], but that's still stuck... > > [1] https://lore.kernel.org/r/1624924520-17567-2-git-send-email-schmitzmic@gmail.com/
That patch (for reasons I never found out) did interact badly with Christoph Hellwig's 'remove set_fs' patches (and Al's signal fixes which Christoph's patches are based upon). Caused format errors under memory stress tests quite reliably, on my 030 hardware.
Probably needs a fresh look - the signal return path got changed by Al's patches IIRC, and I might have relied on offsets to data on the stack that are no longer correct with these patches. Or there's a race between the syscall trap and signal handling when returning from interrupt context ...
Still school hols over here so I won't have much peace and quiet until February.
Cheers,
Michael
> > Gr{oetje,eeting}s, > > Geert > > -- > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org > > In personal conversations with technical people, I call myself a hacker. But > when I'm talking to journalists I just say "programmer" or something like that. > -- Linus Torvalds >
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