Hi Geert,

thanks for the feedback!

As far as I understand, Eric's 'refactor exit()' patch series has 
obsoleted this band-aid fix of mine. The last remnant of code using 
do_exit() is our fpsp040 copyin/copyout exception handling, and there's 
another patch in testing for that. (I'd need access to a 040 hardware 
setup to properly test that one, but that's a different matter.)

Eric, Andreas - please correct me if I'm wrong (again).

Just out of interest - what would be the correct way to set/clear a 
single bit on Coldfire? Add/subtract the 1<<bit value?

Cheers,

     Michael


On 25/07/21 10:05 pm, Geert Uytterhoeven wrote:

Hi Michael,

On Wed, Jun 23, 2021 at 2:21 AM Michael Schmitz [off-list ref] wrote:

quoted

Add 'status' field to thread_info struct to hold syscall trace
status info.

Set flag bit in thread_info->status at syscall trace entry, clear
flag bit on trace exit.

Set another flag bit on entering syscall where the full stack
frame has been saved. These flags can be checked whenever a
syscall calls ptrace_stop().

Check flag bits in get_reg()/put_reg() and prevent access to
registers that are saved on the switch stack, in case the
syscall did not actually save these registers on the switch
stack.

Tested on ARAnyM only - boots and survives running strace on a
binary, nothing fancy.

CC: Eric W. Biederman <redacted>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Andreas Schwab <redacted>
Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>

Thanks for your patch!

quoted

--- a/arch/m68k/kernel/entry.S
+++ b/arch/m68k/kernel/entry.S

@@ -51,75 +51,115 @@

  .text
  ENTRY(__sys_fork)
+       movel   %curptr@(TASK_STACK),%a1
+       orb     #TIS_SWITCH_STACK, %a1@(TINFO_STATUS+3)

This doesn't work on Coldfire:

arch/m68k/kernel/entry.S:55: Error: invalid instruction for this
architecture; needs 68000 or higher (68000 [68ec000, 68hc000, 68hc001,
68008, 68302, 68306, 68307, 68322, 68356], 68010, 68020 [68k,
68ec020], 68030 [68ec030], 68040 [68ec040], 68060 [68ec060], cpu32
[68330, 68331, 68332,
  68333, 68334, 68336, 68340, 68341, 68349, 68360], fidoa [fido]) --
statement `orb #(1<<1),%a1@(16+3)' ignored

quoted

         SAVE_SWITCH_STACK
         jbsr    sys_fork
         lea     %sp@(24),%sp
+       movel   %curptr@(TASK_STACK),%a1
+       andb    #TIS_NO_SWITCH_STACK, %a1@(TINFO_STATUS+3)

arch/m68k/kernel/entry.S:60: Error: invalid instruction for this
architecture; needs 68000 or higher (68000 [68ec000, 68hc000, 68hc001,
68008, 68302, 68306, 68307, 68322, 68356], 68010, 68020 [68k,
68ec020], 68030 [68ec030], 68040 [68ec040], 68060 [68ec060], cpu32
[68330, 68331, 68332, 68333, 68334, 68336, 68340, 68341, 68349,
68360], fidoa [fido]) -- statement `andb #(~((1<<1))),%a1@(16+3)'
ignored

quoted

         rts

Gr{oetje,eeting}s,

                         Geert