[src/netbsd-8]: src/sys/arch/m68k/m68k Pull up following revision(s) (request...

[martin <martin%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/6a21972f0e06
branches:  netbsd-8
changeset: 953069:6a21972f0e06
user:      martin <martin%NetBSD.org@localhost>
date:      Thu Feb 25 09:38:48 2021 +0000

description:
Pull up following revision(s) (requested by tsutsui in ticket #1659):

        sys/arch/m68k/m68k/reenter_syscall.s: revision 1.5
        sys/arch/m68k/m68k/reenter_syscall.s: revision 1.6
        sys/arch/m68k/m68k/reenter_syscall.s: revision 1.7

Replace magic numbers with proper macros prepared in assym.h.

No binary changes.

Note this is a preparation for a possible fix of PR port-m68k/55990.

Consistently use motorola style.  No binary changes.
Seems missed in rev 1.3:
 https://mail-index.netbsd.org/source-changes/2013/08/01/msg046378.html

Plug kernel stack leaks in reenter_syscall() for setcontext(2).
This fixes long standing kernel crashes (MMU fault, address error,
and silent freeze by a double bus fault etc. seen for ~10 years)
caused by kernel stack overflow, especially on x68k and sun3 running
Xorg based servers.  See PR/55990 for more details.

"This change seems perfectly reasonable" from thorpej@ and
jklos@ also reported this also solved freeze of his mac68k system
with 10 megabyes of memory.

Should be pulled up to netbsd-9 and netbsd-8.

diffstat:

 sys/arch/m68k/m68k/reenter_syscall.s |  22 ++++++++++++++++++----
 1 files changed, 18 insertions(+), 4 deletions(-)

diffs (52 lines):

diff -r 92b82f322d20 -r 6a21972f0e06 sys/arch/m68k/m68k/reenter_syscall.s
--- a/sys/arch/m68k/m68k/reenter_syscall.s      Tue Feb 23 18:57:36 2021 +0000
+++ b/sys/arch/m68k/m68k/reenter_syscall.s      Thu Feb 25 09:38:48 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: reenter_syscall.s,v 1.4 2013/09/07 19:06:29 chs Exp $  */
+/*     $NetBSD: reenter_syscall.s,v 1.4.22.1 2021/02/25 09:38:48 martin Exp $  */
 
 /*
  * Written by ITOH Yasufumi.
@@ -6,6 +6,7 @@
  */
 
 #include <m68k/asm.h>
+#include "assym.h"
 
 /*
  * void reenter_syscall(struct frame *fp, int stkadj)
@@ -38,18 +39,31 @@
 .Lcpfr:        movel   (%a0)+,(%a1)+
        dbra    %d0,.Lcpfr
 
-       movew   %d1,%sp@(16*4+2)        | set stack adjust count
+       movew   %d1,FR_ADJ(%sp)         | set stack adjust count
        movel   (%sp),-(%sp)            | push syscall no (original d0 value)
        jbsr    _C_LABEL(syscall)       | re-enter syscall()
        addql   #4,%sp                  | pop syscall no
 #ifdef DEBUG
-       tstw    %sp@(16*4+2)            | stack adjust must be zero
+       tstw    FR_ADJ(%sp)             | stack adjust must be zero
        jeq     .Ladjzero
        PANIC("reenter_syscall")
 .Ladjzero:
 #endif
-       moveal  %sp@(15*4),%a0          | grab and restore
+       moveal  FR_SP(%sp),%a0          | grab and restore
        movel   %a0,%usp                |   user SP
+       movw    FR_ADJ(%sp),%d0         | need to adjust stack?
+       jne     .Ladjstk                | yes, go to it
        moveml  (%sp)+,#0x7FFF          | restore user registers
        addql   #8,%sp                  | pop SP and stack adjust
        jra     _ASM_LABEL(rei)         | rte
+.Ladjstk:
+       lea     FR_HW(%sp),%a1          | pointer to HW frame
+       addql   #8,%a1                  | source pointer
+       movl    %a1,%a0                 | source
+       addw    %d0,%a0                 |  + hole size = dest pointer
+       movl    -(%a1),-(%a0)           | copy
+       movl    -(%a1),-(%a0)           |  8 bytes
+       movl    %a0,FR_SP(%sp)          | new SSP
+       moveml  (%sp)+,#0x7FFF          | restore user register
+       movl    (%sp),%sp               | and do real RTE
+       jra     _ASM_LABEL(rei)         | rte