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@xxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
As this depends on the removal of a parameter from
ptrace_report_syscall() earlier in this series:
Acked-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
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@xxxxxxxxx/
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@xxxxxxxxxxxxxx
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
