[gcc r13-6545] libgcc, rs6000: Fix bump size for powerpc64 elfv1 ABI [PR108727]

[gcc r13-6545] libgcc, rs6000: Fix bump size for powerpc64 elfv1 ABI [PR108727]

[Kewen Lin]

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.

Diff:
---
 libgcc/config/rs6000/morestack.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

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