So, forever, we've had this ptrace_signal_deliver implementation
which tries to handle all of the nasties that can occur when the
debugger looks at a process about to take a signal.  It's meant
to address all of these issues inside of the kernel so that the
debugger need not be mindful of such things.

Problem is, this doesn't work.

The idea was that we should do the syscall restart business first, so
that the debugger captures that state.  Otherwise, if the debugger for
example saves the child's state, makes the child execute something
else, then restores the saved state, we won't handle the syscall
restart properly because we lose the "we're in a syscall" state.

The code here worked for most cases, but if the debugger actually
passes the signal through to the child unaltered, it's possible that
we would do a syscall restart when we shouldn't have.

In particular this breaks the case of debugging a process under a gdb
which is being debugged by yet another gdb.  gdb uses sigsuspend
to wait for SIGCHLD of the inferior, but if gdb itself is being
debugged by a top-level gdb we get a ptrace_stop().  The top-level gdb
does a PTRACE_CONT with SIGCHLD to let the inferior gdb see the
signal.  But ptrace_signal_deliver() assumed the debugger would cancel
out the signal and therefore did a syscall restart, because the return
error was ERESTARTNOHAND.

Fix this by simply making ptrace_signal_deliver() a nop, and providing
a way for the debugger to control system call restarting properly:

1) Report a "in syscall" software bit in regs->{tstate,psr}.
   It is set early on in trap entry to a system call and is fully
   visible to the debugger via ptrace() and regsets.

2) Test this bit right before doing a syscall restart.  We have
   to do a final recheck right after get_signal_to_deliver() in
   case the debugger cleared the bit during ptrace_stop().

3) Clear the bit in trap return so we don't accidently try to set
   that bit in the real register.

As a result we also get a ptrace_{is,clear}_syscall() for sparc32 just
like sparc64 has.

M68K has this same exact bug, and is now the only other user of the
ptrace_signal_deliver hook.  It needs to be fixed in the same exact
way as sparc.

Signed-off-by: David S. Miller <davem@davemloft.net>

Current limitations:

1) On SMP single stepping has some fundamental issues,
   shared with other sw single-step architectures such
   as mips and arm.

2) On 32-bit sparc we don't support SMP kgdb yet.  That
   requires some reworking of the IPI mechanisms and
   infrastructure on that platform.

Signed-off-by: David S. Miller <davem@davemloft.net>

The following cleanups are now possible:
- arch/sparc/kernel/entry.S:ret_sys_call no longer has to be global
- arch/sparc/kernel/signal.c:sys_sigpause() can be removed

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

As per Documentation/feature-removal-schedule.txt

Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: David S. Miller <davem@davemloft.net>

__ndelay and __udelay have not been delayung >= specified time.
The problem with __ndelay has been tacked down to the rounding of the
multiplier constant. By changing this, delays > app 18us are correctly
calculated.
The problem with __udelay has also been tracked down to rounding issues.
Changing the multiplier constant (to match that used in sparc64) corrects
for large delays and adding in a rounding constant corrects for trunctaion
errors in the claculations.
Many short delays will return without looping. This is not an error as there
is the fixed delay of doing all the maths to calculate the loop count.

Signed-off-by: Mark Fortescue <mark@mtfhpc.demon.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

When I added the entries for the robust futex syscall entries, I
forgot to bump NR_SYSCALLS.  The current situation is error-prone
because NR_SYSCALLS lives in entry.S where the system call limit
checks are enforced.  Move the definition to asm/unistd.h in order to
make this mistake much more difficult to make.

And wire up sys_migrate_pages since the powerpc folks implemented the
compat wrapper for us.

Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Jörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

Also, the Solaris syscall table is sized differrently,
and does not go beyond entry 255, so trim off the excess
entries.

Signed-off-by: David S. Miller <davem@davemloft.net>