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| author | Ævar Arnfjörð Bjarmason <avarab@gmail.com> | 2022-08-31 09:18:43 (GMT) |
|---|---|---|
| committer | Junio C Hamano <gitster@pobox.com> | 2022-08-31 21:37:31 (GMT) |
| commit | 9dc523aa0e20271cfe1474bef9fafbe62b7ff603 (patch) | |
| tree | 9e75110b9b63173053fadb0d7c9a2f02e7961b27 /Makefile | |
| parent | d42b38dfb5edf1a7fddd9542d722f91038407819 (diff) | |
| download | git-9dc523aa0e20271cfe1474bef9fafbe62b7ff603.zip git-9dc523aa0e20271cfe1474bef9fafbe62b7ff603.tar.gz git-9dc523aa0e20271cfe1474bef9fafbe62b7ff603.tar.bz2 | |
Makefile + hash.h: remove PPC_SHA1 implementation
Remove the PPC_SHA1 implementation added in a6ef3518f9a ([PATCH] PPC
assembly implementation of SHA1, 2005-04-22). When this was added
Apple consumer hardware used the PPC architecture, and the
implementation was intended to improve SHA-1 speed there.
Since it was added we've moved to using sha1collisiondetection by
default, and anyone wanting hard-rolled non-DC SHA-1 implementation
can use OpenSSL's via the OPENSSL_SHA1 knob.
The PPC_SHA1 originally originally targeted 32 bit PPC, and later the
64 bit PPC 970 (a.k.a. Apple PowerPC G5). See 926172c5e48 (block-sha1:
improve code on large-register-set machines, 2009-08-10) for a
reference about the performance on G5 (a comment in block-sha1/sha1.c
being removed here).
I can't get it to do anything but segfault on both the BE and LE POWER
machines in the GCC compile farm[1]. Anyone who's concerned about
performance on PPC these days is likely to be using the IBM POWER
processors.
There have been proposals to entirely remove non-sha1collisiondetection
implementations from the tree[2]. I think per [3] that would be a bit
overzealous. I.e. there are various set-ups git's speed is going to be
more important than the relatively implausible SHA-1 collision attack,
or where such attacks are entirely mitigated by other means (e.g. by
incoming objects being checked with DC_SHA1).
But that really doesn't apply to PPC_SHA1 in particular, which seems
to have outlived its usefulness.
As this gets rid of the only in-tree *.S assembly file we can remove
the small bits of logic from the Makefile needed to build objects
from *.S (as opposed to *.c)
The code being removed here was also throwing warnings with the
"-pedantic" flag, it could have been fixed as 544d93bc3b4 (block-sha1:
remove use of obsolete x86 assembly, 2022-03-10) did for block-sha1/*,
but as noted above let's remove it instead.
1. https://cfarm.tetaneutral.net/machines/list/
Tested on gcc{110,112,135,203}, a mixture of POWER [789] ppc64 and
ppc64le. All segfault in anything needing object
hashing (e.g. t/t1007-hash-object.sh) when compiled with
PPC_SHA1=Y.
2. https://lore.kernel.org/git/20200223223758.120941-1-mh@glandium.org/
3. https://lore.kernel.org/git/20200224044732.GK1018190@coredump.intra.peff.net/
Acked-by: brian m. carlson" <sandals@crustytoothpaste.net>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'Makefile')
| -rw-r--r-- | Makefile | 18 |
1 files changed, 5 insertions, 13 deletions
@@ -155,9 +155,6 @@ include shared.mak # Define BLK_SHA1 environment variable to make use of the bundled # optimized C SHA1 routine. # -# Define PPC_SHA1 environment variable when running make to make use of -# a bundled SHA1 routine optimized for PowerPC. -# # Define DC_SHA1 to unconditionally enable the collision-detecting sha1 # algorithm. This is slower, but may detect attempted collision attacks. # Takes priority over other *_SHA1 knobs. @@ -1802,6 +1799,10 @@ ifdef APPLE_COMMON_CRYPTO SHA1_MAX_BLOCK_SIZE = 1024L*1024L*1024L endif +ifdef PPC_SHA1 +$(error the PPC_SHA1 flag has been removed along with the PowerPC-specific SHA-1 implementation.) +endif + ifdef OPENSSL_SHA1 EXTLIBS += $(LIB_4_CRYPTO) BASIC_CFLAGS += -DSHA1_OPENSSL @@ -1810,10 +1811,6 @@ ifdef BLK_SHA1 LIB_OBJS += block-sha1/sha1.o BASIC_CFLAGS += -DSHA1_BLK else -ifdef PPC_SHA1 - LIB_OBJS += ppc/sha1.o ppc/sha1ppc.o - BASIC_CFLAGS += -DSHA1_PPC -else ifdef APPLE_COMMON_CRYPTO COMPAT_CFLAGS += -DCOMMON_DIGEST_FOR_OPENSSL BASIC_CFLAGS += -DSHA1_APPLE @@ -1847,7 +1844,6 @@ endif endif endif endif -endif ifdef OPENSSL_SHA256 EXTLIBS += $(LIB_4_CRYPTO) @@ -2594,14 +2590,10 @@ missing_compdb_dir = compdb_args = endif -ASM_SRC := $(wildcard $(OBJECTS:o=S)) -ASM_OBJ := $(ASM_SRC:S=o) -C_OBJ := $(filter-out $(ASM_OBJ),$(OBJECTS)) +C_OBJ := $(OBJECTS) $(C_OBJ): %.o: %.c GIT-CFLAGS $(missing_dep_dirs) $(missing_compdb_dir) $(QUIET_CC)$(CC) -o $*.o -c $(dep_args) $(compdb_args) $(ALL_CFLAGS) $(EXTRA_CPPFLAGS) $< -$(ASM_OBJ): %.o: %.S GIT-CFLAGS $(missing_dep_dirs) $(missing_compdb_dir) - $(QUIET_CC)$(CC) -o $*.o -c $(dep_args) $(compdb_args) $(ALL_CFLAGS) $(EXTRA_CPPFLAGS) $< %.s: %.c GIT-CFLAGS FORCE $(QUIET_CC)$(CC) -o $@ -S $(ALL_CFLAGS) $(EXTRA_CPPFLAGS) $< |