m68k: ptrace fixes

This fixes the following issues in ptrace:

- when single stepping into the signal handler stop at the first insn of
  the handler
- handle non-zero stkadj when accessing pc and sr in ptregs
- correctly handle PT_SR in PTRACE_POKEUSR
- report -EIO when trying to read unknown offset in PTRACE_PEEKUSR

Additionally, the handling of the special case that PT_SR accesses a 16
bit word instead of a 32 bit word has been moved into get_reg/put_reg.

Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/m68k/kernel/entry.S b/arch/m68k/kernel/entry.S
index c5b33634c980..77fc7c16bf48 100644
--- a/arch/m68k/kernel/entry.S
+++ b/arch/m68k/kernel/entry.S
@@ -179,7 +179,11 @@ do_signal_return:
         addql   #8,%sp
         RESTORE_SWITCH_STACK
         addql   #4,%sp
-        jbra    resume_userspace
+        tstl    %d0
+        jeq     resume_userspace
+        | when single stepping into handler stop at the first insn
+        btst    #6,%curptr@(TASK_INFO+TINFO_FLAGS+2)
+        jeq     resume_userspace
 
 do_delayed_trace:
         bclr    #7,%sp@(PT_OFF_SR)      | clear trace bit in SR