[Bug testsuite/108727] New: gcc.dg/split-5.c fails on power 9 BE

[Bug testsuite/108727] New: gcc.dg/split-5.c fails on power 9 BE

[seurer at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108727

            Bug ID: 108727
           Summary: gcc.dg/split-5.c fails on power 9 BE
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: testsuite
          Assignee: unassigned at gcc dot gnu.org
          Reporter: seurer at gcc dot gnu.org
  Target Milestone: ---

g:6ad1c1027628f094260037536f6b6fcdb63b5add, r13-5742-g6ad1c1027628f0

This fails on power 9 BE.  Note that on earlier hardware levels it is just
unsupported.

make  -k check-gcc RUNTESTFLAGS="--target_board=unix'{-m32,-m64}'
dg.exp=gcc.dg/split-5.c"
FAIL: gcc.dg/split-5.c execution test
# of unexpected failures        1
# of unexpected failures        1
# of unsupported tests          1
# of unsupported tests          1

[Bug testsuite/108727] gcc.dg/split-5.c fails on power 9 BE

[linkw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108727

Kewen Lin <linkw at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |linkw at gcc dot gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2023-03-01
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |linkw at gcc dot gnu.org

--- Comment #1 from Kewen Lin <linkw at gcc dot gnu.org> ---
Confirmed, probably expose one bug in libgcc related support, I'll have a look
first.

[Bug libgcc/108727] gcc.dg/split-5.c fails on power 9 BE

[linkw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108727

Kewen Lin <linkw at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |amodra at gcc dot gnu.org,
                   |                            |amodra at gmail dot com,
                   |                            |segher at gcc dot gnu.org

--- Comment #2 from Kewen Lin <linkw at gcc dot gnu.org> ---
This is one bug in libgcc morestack support (powerpc64 elfv1 ABI specific):

The segfault happens on:

Dump of assembler code for function 00000000.plt_call._Unwind_Resume:
=> 0x0000000010003580 <+0>:     std     r2,40(r1)
   0x0000000010003584 <+4>:     ld      r12,-31760(r2)
   0x0000000010003588 <+8>:     mtctr   r12
   0x000000001000358c <+12>:    ld      r2,-31752(r2)
   0x0000000010003590 <+16>:    cmpldi  r2,0
   0x0000000010003594 <+20>:    bnectr+
   0x0000000010003598 <+24>:    b       0x100031a4 <_Unwind_Resume@plt>
   0x000000001000359c <+28>:    .long 0x0

The target address of std at 0x0000000010003580 is 0x7ffff72e0008, which isn't
writable as the following mappings:

   0x7ffff40f0000     0x7ffff72e0000  0x31f0000        0x0  rw-p
   0x7ffff72e0000     0x7ffff72f0000    0x10000        0x0  ---p

For the stack segment returned from __generic_morestack, we adjust it by 32
bytes:

   bl JUMP_TARGET(__generic_morestack)

   # Start using new stack
   stdu %r29,-32(%r3)           # back-chain
   mr %r1,%r3

but it isn't enough for powerpc64 elfv1 ABI as the TOC base save slot is with
offset 40.

The fix can be to use PARAMS like:

diff --git a/libgcc/config/rs6000/morestack.S
b/libgcc/config/rs6000/morestack.S
index 5e7ad133303..f2fea6abb10 100644
--- a/libgcc/config/rs6000/morestack.S
+++ b/libgcc/config/rs6000/morestack.S
@@ -205,12 +205,12 @@ ENTRY0(__morestack)
         bl JUMP_TARGET(__generic_morestack)

 # Start using new stack
-        stdu %r29,-32(%r3)              # back-chain
+        stdu %r29,-PARAMS(%r3)          # back-chain
         mr %r1,%r3

 # Set __private_ss stack guard for the new stack.
         ld %r12,NEWSTACKSIZE_SAVE(%r29) # modified size
-        addi %r3,%r3,BACKOFF-32
+        addi %r3,%r3,BACKOFF-PARAMS
         sub %r3,%r3,%r12
 # Note that a signal frame has $pc pointing at the instruction
 # where the signal occurred.  For something like a timer

============================================================

Hi Alan, does the above fix look reasonable to you?

[Bug libgcc/108727] gcc.dg/split-5.c fails on power 9 BE

[amodra at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108727

--- Comment #3 from Alan Modra <amodra at gmail dot com> ---
Yes, looks good to me.

[Bug libgcc/108727] gcc.dg/split-5.c fails on power 9 BE

[linkw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108727

Kewen Lin <linkw at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |https://gcc.gnu.org/piperma
                   |                            |il/gcc-patches/2023-March/6
                   |                            |13441.html

--- Comment #4 from Kewen Lin <linkw at gcc dot gnu.org> ---
(In reply to Alan Modra from comment #3)
> Yes, looks good to me.

Thanks Alan! An formal patch was posted as URL field.

[Bug libgcc/108727] gcc.dg/split-5.c fails on power 9 BE

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108727

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Kewen Lin <linkw@gcc.gnu.org>:

https://gcc.gnu.org/g:15b83b69ca99d97643075776ba94f2dd1f05b46e

commit r13-6545-g15b83b69ca99d97643075776ba94f2dd1f05b46e
Author: Kewen Lin <linkw@linux.ibm.com>
Date:   Wed Mar 8 00:57:21 2023 -0600

    libgcc, rs6000: Fix bump size for powerpc64 elfv1 ABI [PR108727]

    As PR108727 shows, when cleanup code called by the stack
    unwinder calls function _Unwind_Resume, it goes via plt
    stub like:

       function 00000000.plt_call._Unwind_Resume:

    => 0x0000000010003580 <+0>:     std     r2,40(r1)
       0x0000000010003584 <+4>:     ld      r12,-31760(r2)
       0x0000000010003588 <+8>:     mtctr   r12
       0x000000001000358c <+12>:    ld      r2,-31752(r2)
       0x0000000010003590 <+16>:    cmpldi  r2,0
       0x0000000010003594 <+20>:    bnectr+
       0x0000000010003598 <+24>:    b       0x100031a4
                                            <_Unwind_Resume@plt>

    It wants to save TOC base (r2) to r1 + 40, but we only
    bump the stack segment by 32 bytes as follows:

       stdu %r29,-32(%r3)

    It means the access is out of the stack segment allocated
    by __generic_morestack, once the touch area isn't writable
    like this failure shows, it would cause segment fault.

    So fix the bump size with one reasonable value PARAMS.

            PR libgcc/108727

    libgcc/ChangeLog:

            * config/rs6000/morestack.S (__morestack): Use PARAMS for new stack
            bump size.

[Bug libgcc/108727] gcc.dg/split-5.c fails on power 9 BE

[linkw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108727

Kewen Lin <linkw at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #6 from Kewen Lin <linkw at gcc dot gnu.org> ---
Should be fixed on trunk.