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s390: select ARCH_SUPPORTS_INT128

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s390 has instructions to support 128 bit arithmetics, e.g. a 64 bit
multiply instruction with a 128 bit result. Also 128 bit integer
artithmetics are already used in s390 specific architecture code (see
e.g. read_persistent_clock64()).

Therefore select ARCH_SUPPORTS_INT128.

However limit this to clang for now, since gcc generates inefficient code,
which may lead to stack overflows, when compiling
lib/crypto/curve25519-hacl64.c which depends on ARCH_SUPPORTS_INT128. The
gcc generated functions have 6kb stack frames, compared to only 1kb of the
code generated with clang.

If the kernel is compiled with -Os library calls for __ashlti3(),
__ashrti3(), and __lshrti3() may be generated. Similar to arm64
and riscv provide assembler implementations for these functions.

Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2023-04-25 13:42:11 +02:00 committed by Alexander Gordeev
parent 1f2597cd36
commit fbac266f09
4 changed files with 69 additions and 1 deletions
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1
arch/s390/Kconfig
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@ -117,6 +117,7 @@ config S390
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_SUPPORTS_DEBUG_PAGEALLOC
select ARCH_SUPPORTS_HUGETLBFS
select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && CC_IS_CLANG
select ARCH_SUPPORTS_NUMA_BALANCING
select ARCH_SUPPORTS_PER_VMA_LOCK
select ARCH_USE_BUILTIN_BSWAP

4
arch/s390/include/asm/asm-prototypes.h
View File

@ -6,4 +6,8 @@
#include <asm/fpu/api.h>
#include <asm-generic/asm-prototypes.h>
__int128_t __ashlti3(__int128_t a, int b);
__int128_t __ashrti3(__int128_t a, int b);
__int128_t __lshrti3(__int128_t a, int b);
#endif /* _ASM_S390_PROTOTYPES_H */

2
arch/s390/lib/Makefile
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@ -3,7 +3,7 @@
# Makefile for s390-specific library files..
#
lib-y += delay.o string.o uaccess.o find.o spinlock.o
lib-y += delay.o string.o uaccess.o find.o spinlock.o tishift.o
obj-y += mem.o xor.o
lib-$(CONFIG_KPROBES) += probes.o
lib-$(CONFIG_UPROBES) += probes.o

63
arch/s390/lib/tishift.S Normal file
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@ -0,0 +1,63 @@
/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/linkage.h>
#include <asm/nospec-insn.h>
#include <asm/export.h>
.section .noinstr.text, "ax"
GEN_BR_THUNK %r14
SYM_FUNC_START(__ashlti3)
lmg %r0,%r1,0(%r3)
cije %r4,0,1f
lhi %r3,64
sr %r3,%r4
jnh 0f
srlg %r3,%r1,0(%r3)
sllg %r0,%r0,0(%r4)
sllg %r1,%r1,0(%r4)
ogr %r0,%r3
j 1f
0: sllg %r0,%r1,-64(%r4)
lghi %r1,0
1: stmg %r0,%r1,0(%r2)
BR_EX %r14
SYM_FUNC_END(__ashlti3)
EXPORT_SYMBOL(__ashlti3)
SYM_FUNC_START(__ashrti3)
lmg %r0,%r1,0(%r3)
cije %r4,0,1f
lhi %r3,64
sr %r3,%r4
jnh 0f
sllg %r3,%r0,0(%r3)
srlg %r1,%r1,0(%r4)
srag %r0,%r0,0(%r4)
ogr %r1,%r3
j 1f
0: srag %r1,%r0,-64(%r4)
srag %r0,%r0,63
1: stmg %r0,%r1,0(%r2)
BR_EX %r14
SYM_FUNC_END(__ashrti3)
EXPORT_SYMBOL(__ashrti3)
SYM_FUNC_START(__lshrti3)
lmg %r0,%r1,0(%r3)
cije %r4,0,1f
lhi %r3,64
sr %r3,%r4
jnh 0f
sllg %r3,%r0,0(%r3)
srlg %r1,%r1,0(%r4)
srlg %r0,%r0,0(%r4)
ogr %r1,%r3
j 1f
0: srlg %r1,%r0,-64(%r4)
lghi %r0,0
1: stmg %r0,%r1,0(%r2)
BR_EX %r14
SYM_FUNC_END(__lshrti3)
EXPORT_SYMBOL(__lshrti3)