ec6347bb43
In reaction to a proposal to introduce a memcpy_mcsafe_fast() implementation Linus points out that memcpy_mcsafe() is poorly named relative to communicating the scope of the interface. Specifically what addresses are valid to pass as source, destination, and what faults / exceptions are handled. Of particular concern is that even though x86 might be able to handle the semantics of copy_mc_to_user() with its common copy_user_generic() implementation other archs likely need / want an explicit path for this case: On Fri, May 1, 2020 at 11:28 AM Linus Torvalds <torvalds@linux-foundation.org> wrote: > > On Thu, Apr 30, 2020 at 6:21 PM Dan Williams <dan.j.williams@intel.com> wrote: > > > > However now I see that copy_user_generic() works for the wrong reason. > > It works because the exception on the source address due to poison > > looks no different than a write fault on the user address to the > > caller, it's still just a short copy. So it makes copy_to_user() work > > for the wrong reason relative to the name. > > Right. > > And it won't work that way on other architectures. On x86, we have a > generic function that can take faults on either side, and we use it > for both cases (and for the "in_user" case too), but that's an > artifact of the architecture oddity. > > In fact, it's probably wrong even on x86 - because it can hide bugs - > but writing those things is painful enough that everybody prefers > having just one function. Replace a single top-level memcpy_mcsafe() with either copy_mc_to_user(), or copy_mc_to_kernel(). Introduce an x86 copy_mc_fragile() name as the rename for the low-level x86 implementation formerly named memcpy_mcsafe(). It is used as the slow / careful backend that is supplanted by a fast copy_mc_generic() in a follow-on patch. One side-effect of this reorganization is that separating copy_mc_64.S to its own file means that perf no longer needs to track dependencies for its memcpy_64.S benchmarks. [ bp: Massage a bit. ] Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Tony Luck <tony.luck@intel.com> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Cc: <stable@vger.kernel.org> Link: http://lore.kernel.org/r/CAHk-=wjSqtXAqfUJxFtWNwmguFASTgB0dz1dT3V-78Quiezqbg@mail.gmail.com Link: https://lkml.kernel.org/r/160195561680.2163339.11574962055305783722.stgit@dwillia2-desk3.amr.corp.intel.com
59 lines
1.8 KiB
Makefile
59 lines
1.8 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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# The loops are all 64-bit code
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CFLAGS += -m64
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CFLAGS += -I$(CURDIR)
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CFLAGS += -D SELFTEST
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CFLAGS += -maltivec
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CFLAGS += -mcpu=power4
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# Use our CFLAGS for the implicit .S rule & set the asm machine type
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ASFLAGS = $(CFLAGS) -Wa,-mpower4
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TEST_GEN_PROGS := copyuser_64_t0 copyuser_64_t1 copyuser_64_t2 \
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copyuser_p7_t0 copyuser_p7_t1 \
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memcpy_64_t0 memcpy_64_t1 memcpy_64_t2 \
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memcpy_p7_t0 memcpy_p7_t1 copy_mc_64 \
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copyuser_64_exc_t0 copyuser_64_exc_t1 copyuser_64_exc_t2
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EXTRA_SOURCES := validate.c ../harness.c stubs.S
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top_srcdir = ../../../../..
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include ../../lib.mk
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$(OUTPUT)/copyuser_64_t%: copyuser_64.S $(EXTRA_SOURCES)
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$(CC) $(CPPFLAGS) $(CFLAGS) \
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-D COPY_LOOP=test___copy_tofrom_user_base \
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-D SELFTEST_CASE=$(subst copyuser_64_t,,$(notdir $@)) \
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-o $@ $^
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$(OUTPUT)/copyuser_p7_t%: copyuser_power7.S $(EXTRA_SOURCES)
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$(CC) $(CPPFLAGS) $(CFLAGS) \
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-D COPY_LOOP=test___copy_tofrom_user_power7 \
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-D SELFTEST_CASE=$(subst copyuser_p7_t,,$(notdir $@)) \
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-o $@ $^
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# Strictly speaking, we only need the memcpy_64 test cases for big-endian
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$(OUTPUT)/memcpy_64_t%: memcpy_64.S $(EXTRA_SOURCES)
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$(CC) $(CPPFLAGS) $(CFLAGS) \
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-D COPY_LOOP=test_memcpy \
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-D SELFTEST_CASE=$(subst memcpy_64_t,,$(notdir $@)) \
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-o $@ $^
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$(OUTPUT)/memcpy_p7_t%: memcpy_power7.S $(EXTRA_SOURCES)
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$(CC) $(CPPFLAGS) $(CFLAGS) \
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-D COPY_LOOP=test_memcpy_power7 \
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-D SELFTEST_CASE=$(subst memcpy_p7_t,,$(notdir $@)) \
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-o $@ $^
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$(OUTPUT)/copy_mc_64: copy_mc_64.S $(EXTRA_SOURCES)
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$(CC) $(CPPFLAGS) $(CFLAGS) \
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-D COPY_LOOP=test_copy_mc_generic \
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-o $@ $^
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$(OUTPUT)/copyuser_64_exc_t%: copyuser_64.S exc_validate.c ../harness.c \
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copy_tofrom_user_reference.S stubs.S
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$(CC) $(CPPFLAGS) $(CFLAGS) \
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-D COPY_LOOP=test___copy_tofrom_user_base \
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-D SELFTEST_CASE=$(subst copyuser_64_exc_t,,$(notdir $@)) \
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-o $@ $^
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