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[POWER10] __morestack calls from pcrel code

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Compiling gcc/testsuite/gcc.dg/split-*.c and others with -mcpu=power10
and linking with a non-pcrel libgcc results in crashes due to the
power10 pcrel code not having r2 set for the generic-morestack.c
functions called from __morestack.  There is also a problem when
non-pcrel code calls a pcrel libgcc.  See the patch comments.

A similar situation theoretically occurs with ELFv1 multi-toc
executables, when __morestack might be located in a different toc
group to its caller.  This patch makes no attempt to fix that, since
the gold linker does not support multi-toc (gold is needed for proper
support of -fsplit-stack code) nor does gcc emit __morestack calls
that support multi-toc.

	* config/rs6000/morestack.S (R2_SAVE): Define.
	(__morestack): Save and restore r2.  Set up r2 for called
	functions.
This commit is contained in:
Alan Modra 2021-06-29 13:31:45 +09:30
parent 4f3b383cf8
commit cd6ca96f5d
1 changed files with 41 additions and 0 deletions
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41
libgcc/config/rs6000/morestack.S
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@ -31,6 +31,7 @@
#define PARAMS 48
#endif
#define MORESTACK_FRAMESIZE (PARAMS+96)
#define R2_SAVE -MORESTACK_FRAMESIZE+PARAMS-8
#define PARAMREG_SAVE -MORESTACK_FRAMESIZE+PARAMS+0
#define STATIC_CHAIN_SAVE -MORESTACK_FRAMESIZE+PARAMS+64
#define R29_SAVE -MORESTACK_FRAMESIZE+PARAMS+72
@ -143,6 +144,17 @@ ENTRY0(__morestack_non_split)
# cr7 must also be preserved.
ENTRY0(__morestack)
#if _CALL_ELF == 2
# Functions with localentry bits of zero cannot make calls if those
# calls might change r2. This is true generally, and also true for
# __morestack with its special calling convention. When __morestack's
# caller is non-pcrel but libgcc is pcrel, the functions called here
# might modify r2. r2 must be preserved on exit, and also restored
# for the call back to our caller.
std %r2,R2_SAVE(%r1)
#endif
# Save parameter passing registers, our arguments, lr, r29
# and use r29 as a frame pointer.
std %r3,PARAMREG_SAVE+0(%r1)
@ -161,10 +173,24 @@ ENTRY0(__morestack)
std %r12,LINKREG_SAVE(%r1)
std %r3,NEWSTACKSIZE_SAVE(%r1) # new stack size
mr %r29,%r1
#if _CALL_ELF == 2
.cfi_offset %r2,R2_SAVE
#endif
.cfi_offset %r29,R29_SAVE
.cfi_def_cfa_register %r29
stdu %r1,-MORESTACK_FRAMESIZE(%r1)
#if _CALL_ELF == 2 && !defined __PCREL__
# If this isn't a pcrel libgcc then the functions we call here will
# require r2 to be valid. If __morestack is called from pcrel code r2
# won't be valid. Set it up.
bcl 20,31,1f
1:
mflr %r12
addis %r2,%r12,.TOC.-1b@ha
addi %r2,%r2,.TOC.-1b@l
#endif
# void __morestack_block_signals (void)
bl JUMP_TARGET(__morestack_block_signals)
@ -199,6 +225,9 @@ ENTRY0(__morestack)
# instructions after __morestack's return address.
#
ld %r12,LINKREG_SAVE(%r29)
#if _CALL_ELF == 2
ld %r2,R2_SAVE(%r29)
#endif
ld %r3,PARAMREG_SAVE+0(%r29) # restore arg regs
ld %r4,PARAMREG_SAVE+8(%r29)
ld %r5,PARAMREG_SAVE+16(%r29)
@ -228,6 +257,15 @@ ENTRY0(__morestack)
std %r10,PARAMREG_SAVE+56(%r29)
#endif
#if _CALL_ELF == 2 && !defined __PCREL__
# r2 was restored for calling back into our caller. Set it up again.
bcl 20,31,1f
1:
mflr %r12
addis %r2,%r12,.TOC.-1b@ha
addi %r2,%r2,.TOC.-1b@l
#endif
bl JUMP_TARGET(__morestack_block_signals)
# void *__generic_releasestack (size_t *pavailable)
@ -249,6 +287,9 @@ ENTRY0(__morestack)
# Restore return value regs, and return.
ld %r0,LINKREG_SAVE(%r29)
mtlr %r0
#if _CALL_ELF == 2
ld %r2,R2_SAVE(%r29)
#endif
ld %r3,PARAMREG_SAVE+0(%r29)
ld %r4,PARAMREG_SAVE+8(%r29)
ld %r5,PARAMREG_SAVE+16(%r29)