| Message ID | 20230216234522.3757369-2-elver@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [-tip,v4,1/3] kasan: Emit different calls for instrumentable memintrinsics | expand |
On Fri, Feb 17, 2023 at 12:45 AM Marco Elver <elver@google.com> wrote: > > Where the compiler instruments meminstrinsics by generating calls to > __asan/__hwasan_ prefixed functions, let the compiler consider > memintrinsics as builtin again. > > To do so, never override memset/memmove/memcpy if the compiler does the > correct instrumentation - even on !GENERIC_ENTRY architectures. > > Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions") > Signed-off-by: Marco Elver <elver@google.com> > --- > v4: > * New patch. > --- > lib/Kconfig.kasan | 9 +++++++++ > mm/kasan/shadow.c | 5 ++++- > scripts/Makefile.kasan | 9 +++++++++ > 3 files changed, 22 insertions(+), 1 deletion(-) > > diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan > index be6ee6020290..fdca89c05745 100644 > --- a/lib/Kconfig.kasan > +++ b/lib/Kconfig.kasan > @@ -49,6 +49,15 @@ menuconfig KASAN > > if KASAN > > +config CC_HAS_KASAN_MEMINTRINSIC_PREFIX > + def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=kernel-address -mllvm -asan-kernel-mem-intrinsic-prefix=1)) || \ > + (CC_IS_GCC && $(cc-option,-fsanitize=kernel-address --param asan-kernel-mem-intrinsic-prefix=1)) > + # Don't define it if we don't need it: compilation of the test uses > + # this variable to decide how the compiler should treat builtins. > + depends on !KASAN_HW_TAGS > + help > + The compiler is able to prefix memintrinsics with __asan or __hwasan. > + > choice > prompt "KASAN mode" > default KASAN_GENERIC > diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c > index f8a47cb299cb..43b6a59c8b54 100644 > --- a/mm/kasan/shadow.c > +++ b/mm/kasan/shadow.c > @@ -38,11 +38,14 @@ bool __kasan_check_write(const volatile void *p, unsigned int size) > } > EXPORT_SYMBOL(__kasan_check_write); > > -#ifndef CONFIG_GENERIC_ENTRY > +#if !defined(CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX) && !defined(CONFIG_GENERIC_ENTRY) > /* > * CONFIG_GENERIC_ENTRY relies on compiler emitted mem*() calls to not be > * instrumented. KASAN enabled toolchains should emit __asan_mem*() functions > * for the sites they want to instrument. > + * > + * If we have a compiler that can instrument meminstrinsics, never override > + * these, so that non-instrumented files can safely consider them as builtins. > */ > #undef memset > void *memset(void *addr, int c, size_t len) > diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan > index fa9f836f8039..c186110ffa20 100644 > --- a/scripts/Makefile.kasan > +++ b/scripts/Makefile.kasan > @@ -1,5 +1,14 @@ > # SPDX-License-Identifier: GPL-2.0 > + > +ifdef CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX > +# Safe for compiler to generate meminstrinsic calls in uninstrumented files. > +CFLAGS_KASAN_NOSANITIZE := > +else > +# Don't let compiler generate memintrinsic calls in uninstrumented files > +# because they are instrumented. > CFLAGS_KASAN_NOSANITIZE := -fno-builtin > +endif > + > KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET) > > cc-param = $(call cc-option, -mllvm -$(1), $(call cc-option, --param $(1))) > -- > 2.39.2.637.g21b0678d19-goog > Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com> Is it also safe to remove custom mem* definitions from arch/x86/include/asm/string_64.h now? https://elixir.bootlin.com/linux/v6.2-rc8/source/arch/x86/include/asm/string_64.h#L88
On Fri, 17 Feb 2023 at 12:07, Andrey Konovalov <andreyknvl@gmail.com> wrote: > Is it also safe to remove custom mem* definitions from > arch/x86/include/asm/string_64.h now? > > https://elixir.bootlin.com/linux/v6.2-rc8/source/arch/x86/include/asm/string_64.h#L88 Yes, I think so - sent another patch: https://lore.kernel.org/all/Y+94tm7xoeTGqPgs@elver.google.com/
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan index be6ee6020290..fdca89c05745 100644 --- a/lib/Kconfig.kasan +++ b/lib/Kconfig.kasan @@ -49,6 +49,15 @@ menuconfig KASAN if KASAN +config CC_HAS_KASAN_MEMINTRINSIC_PREFIX + def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=kernel-address -mllvm -asan-kernel-mem-intrinsic-prefix=1)) || \ + (CC_IS_GCC && $(cc-option,-fsanitize=kernel-address --param asan-kernel-mem-intrinsic-prefix=1)) + # Don't define it if we don't need it: compilation of the test uses + # this variable to decide how the compiler should treat builtins. + depends on !KASAN_HW_TAGS + help + The compiler is able to prefix memintrinsics with __asan or __hwasan. + choice prompt "KASAN mode" default KASAN_GENERIC diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c index f8a47cb299cb..43b6a59c8b54 100644 --- a/mm/kasan/shadow.c +++ b/mm/kasan/shadow.c @@ -38,11 +38,14 @@ bool __kasan_check_write(const volatile void *p, unsigned int size) } EXPORT_SYMBOL(__kasan_check_write); -#ifndef CONFIG_GENERIC_ENTRY +#if !defined(CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX) && !defined(CONFIG_GENERIC_ENTRY) /* * CONFIG_GENERIC_ENTRY relies on compiler emitted mem*() calls to not be * instrumented. KASAN enabled toolchains should emit __asan_mem*() functions * for the sites they want to instrument. + * + * If we have a compiler that can instrument meminstrinsics, never override + * these, so that non-instrumented files can safely consider them as builtins. */ #undef memset void *memset(void *addr, int c, size_t len) diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan index fa9f836f8039..c186110ffa20 100644 --- a/scripts/Makefile.kasan +++ b/scripts/Makefile.kasan @@ -1,5 +1,14 @@ # SPDX-License-Identifier: GPL-2.0 + +ifdef CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX +# Safe for compiler to generate meminstrinsic calls in uninstrumented files. +CFLAGS_KASAN_NOSANITIZE := +else +# Don't let compiler generate memintrinsic calls in uninstrumented files +# because they are instrumented. CFLAGS_KASAN_NOSANITIZE := -fno-builtin +endif + KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET) cc-param = $(call cc-option, -mllvm -$(1), $(call cc-option, --param $(1)))
Where the compiler instruments meminstrinsics by generating calls to __asan/__hwasan_ prefixed functions, let the compiler consider memintrinsics as builtin again. To do so, never override memset/memmove/memcpy if the compiler does the correct instrumentation - even on !GENERIC_ENTRY architectures. Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions") Signed-off-by: Marco Elver <elver@google.com> --- v4: * New patch. --- lib/Kconfig.kasan | 9 +++++++++ mm/kasan/shadow.c | 5 ++++- scripts/Makefile.kasan | 9 +++++++++ 3 files changed, 22 insertions(+), 1 deletion(-)