If we use the ancient SysV syscall ABI, we'd better have tell the
kernel how to claim that a negative return value is a success.
Use ->orig_r2 for that - it's inaccessible via ptrace, so it's
a fair game for changes and it's normally[*] non-negative on return
from syscall.  Set to -1; syscall is not going to be restart-worthy
by definition, so we won't interfere with that use either.

[*] the only exception is rt_sigreturn(), where we skip the entire
messing with r1/r2 anyway.

Fixes: 82ed08dd1b0e ("nios2: Exception handling")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

Fixes: b53e906d255d ("nios2: Signal handling support")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

sys_foo() returns -512 (aka -ERESTARTSYS) => do_signal() sees
512 in r2 and 1 in r1.

sys_foo() returns 512 => do_signal() sees 512 in r2 and 0 in r1.

The former is restart-worthy; the latter obviously isn't.

Fixes: b53e906d255d ("nios2: Signal handling support")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

all checks done before letting the tracer modify the register
state are worthless...

Fixes: 82ed08dd1b0e ("nios2: Exception handling")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

fill the gaps in there with sys_ni_syscall, as everyone does...

Fixes: 82ed08dd1b0e ("nios2: Exception handling")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

make sure that ->orig_r2 is negative for everything except
the syscalls.

Fixes: 82ed08dd1b0e ("nios2: Exception handling")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

Add fn and fn_arg members into struct kernel_clone_args and test for
them in copy_thread (instead of testing for PF_KTHREAD | PF_IO_WORKER).
This allows any task that wants to be a user space task that only runs
in kernel mode to use this functionality.

The code on x86 is an exception and still retains a PF_KTHREAD test
because x86 unlikely everything else handles kthreads slightly
differently than user space tasks that start with a function.

The functions that created tasks that start with a function
have been updated to set ".fn" and ".fn_arg" instead of
".stack" and ".stack_size".  These functions are fork_idle(),
create_io_thread(), kernel_thread(), and user_mode_thread().

Link: https://lkml.kernel.org/r/20220506141512.516114-4-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

With io_uring we have started supporting tasks that are for most
purposes user space tasks that exclusively run code in kernel mode.

The kernel task that exec's init and tasks that exec user mode
helpers are also user mode tasks that just run kernel code
until they call kernel execve.

Pass kernel_clone_args into copy_thread so these oddball
tasks can be supported more cleanly and easily.

v2: Fix spelling of kenrel_clone_args on h8300
Link: https://lkml.kernel.org/r/20220506141512.516114-2-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

Pull ptrace cleanups from Eric Biederman:
 "This set of changes removes tracehook.h, moves modification of all of
  the ptrace fields inside of siglock to remove races, adds a missing
  permission check to ptrace.c

  The removal of tracehook.h is quite significant as it has been a major
  source of confusion in recent years. Much of that confusion was around
  task_work and TIF_NOTIFY_SIGNAL (which I have now decoupled making the
  semantics clearer).

  For people who don't know tracehook.h is a vestiage of an attempt to
  implement uprobes like functionality that was never fully merged, and
  was later superseeded by uprobes when uprobes was merged. For many
  years now we have been removing what tracehook functionaly a little
  bit at a time. To the point where anything left in tracehook.h was
  some weird strange thing that was difficult to understand"

* tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  ptrace: Remove duplicated include in ptrace.c
  ptrace: Check PTRACE_O_SUSPEND_SECCOMP permission on PTRACE_SEIZE
  ptrace: Return the signal to continue with from ptrace_stop
  ptrace: Move setting/clearing ptrace_message into ptrace_stop
  tracehook: Remove tracehook.h
  resume_user_mode: Move to resume_user_mode.h
  resume_user_mode: Remove #ifdef TIF_NOTIFY_RESUME in set_notify_resume
  signal: Move set_notify_signal and clear_notify_signal into sched/signal.h
  task_work: Decouple TIF_NOTIFY_SIGNAL and task_work
  task_work: Call tracehook_notify_signal from get_signal on all architectures
  task_work: Introduce task_work_pending
  task_work: Remove unnecessary include from posix_timers.h
  ptrace: Remove tracehook_signal_handler
  ptrace: Remove arch_syscall_{enter,exit}_tracehook
  ptrace: Create ptrace_report_syscall_{entry,exit} in ptrace.h
  ptrace/arm: Rename tracehook_report_syscall report_syscall
  ptrace: Move ptrace_report_syscall into ptrace.h

Move set_notify_resume and tracehook_notify_resume into resume_user_mode.h.
While doing that rename tracehook_notify_resume to resume_user_mode_work.

Update all of the places that included tracehook.h for these functions to
include resume_user_mode.h instead.

Update all of the callers of tracehook_notify_resume to call
resume_user_mode_work.

Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20220309162454.123006-12-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>