* [PATCH 1/2] kasan: Improve and simplify Kconfig.kasan
@ 2020-06-29 10:41 Marco Elver
2020-06-29 10:41 ` [PATCH 2/2] kasan: Update required compiler versions in documentation Marco Elver
2020-06-29 13:34 ` [PATCH 1/2] kasan: Improve and simplify Kconfig.kasan Andrey Konovalov
0 siblings, 2 replies; 4+ messages in thread
From: Marco Elver @ 2020-06-29 10:41 UTC (permalink / raw)
To: elver, akpm
Cc: dvyukov, glider, andreyknvl, linux-kernel, kasan-dev, aryabinin,
ndesaulniers, walter-zh.wu, arnd, dja, linux-doc,
clang-built-linux
Turn 'KASAN' into a menuconfig, to avoid cluttering its parent menu with
the suboptions if enabled. Use 'if KASAN ... endif' instead of having
to 'depend on KASAN' for each entry.
Signed-off-by: Marco Elver <elver@google.com>
---
lib/Kconfig.kasan | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 34b84bcbd3d9..89053defc0d9 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -18,7 +18,7 @@ config CC_HAS_KASAN_SW_TAGS
config CC_HAS_WORKING_NOSANITIZE_ADDRESS
def_bool !CC_IS_GCC || GCC_VERSION >= 80300
-config KASAN
+menuconfig KASAN
bool "KASAN: runtime memory debugger"
depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
(HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)
@@ -29,9 +29,10 @@ config KASAN
designed to find out-of-bounds accesses and use-after-free bugs.
See Documentation/dev-tools/kasan.rst for details.
+if KASAN
+
choice
prompt "KASAN mode"
- depends on KASAN
default KASAN_GENERIC
help
KASAN has two modes: generic KASAN (similar to userspace ASan,
@@ -88,7 +89,6 @@ endchoice
choice
prompt "Instrumentation type"
- depends on KASAN
default KASAN_OUTLINE
config KASAN_OUTLINE
@@ -113,7 +113,6 @@ endchoice
config KASAN_STACK_ENABLE
bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
- depends on KASAN
help
The LLVM stack address sanitizer has a know problem that
causes excessive stack usage in a lot of functions, see
@@ -134,7 +133,7 @@ config KASAN_STACK
config KASAN_S390_4_LEVEL_PAGING
bool "KASan: use 4-level paging"
- depends on KASAN && S390
+ depends on S390
help
Compiling the kernel with KASan disables automatic 3-level vs
4-level paging selection. 3-level paging is used by default (up
@@ -151,7 +150,7 @@ config KASAN_SW_TAGS_IDENTIFY
config KASAN_VMALLOC
bool "Back mappings in vmalloc space with real shadow memory"
- depends on KASAN && HAVE_ARCH_KASAN_VMALLOC
+ depends on HAVE_ARCH_KASAN_VMALLOC
help
By default, the shadow region for vmalloc space is the read-only
zero page. This means that KASAN cannot detect errors involving
@@ -164,8 +163,10 @@ config KASAN_VMALLOC
config TEST_KASAN
tristate "Module for testing KASAN for bug detection"
- depends on m && KASAN
+ depends on m
help
This is a test module doing various nasty things like
out of bounds accesses, use after free. It is useful for testing
kernel debugging features like KASAN.
+
+endif # KASAN
--
2.27.0.212.ge8ba1cc988-goog
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH 2/2] kasan: Update required compiler versions in documentation
2020-06-29 10:41 [PATCH 1/2] kasan: Improve and simplify Kconfig.kasan Marco Elver
@ 2020-06-29 10:41 ` Marco Elver
2020-06-29 13:36 ` Andrey Konovalov
2020-06-29 13:34 ` [PATCH 1/2] kasan: Improve and simplify Kconfig.kasan Andrey Konovalov
1 sibling, 1 reply; 4+ messages in thread
From: Marco Elver @ 2020-06-29 10:41 UTC (permalink / raw)
To: elver, akpm
Cc: dvyukov, glider, andreyknvl, linux-kernel, kasan-dev, aryabinin,
ndesaulniers, walter-zh.wu, arnd, dja, linux-doc,
clang-built-linux
Updates the recently changed compiler requirements for KASAN. In
particular, we require GCC >= 8.3.0, and add a note that Clang 11
supports OOB detection of globals.
Fixes: 7b861a53e46b ("kasan: Bump required compiler version")
Fixes: acf7b0bf7dcf ("kasan: Fix required compiler version")
Signed-off-by: Marco Elver <elver@google.com>
---
Documentation/dev-tools/kasan.rst | 7 ++-----
lib/Kconfig.kasan | 24 +++++++++++++++---------
2 files changed, 17 insertions(+), 14 deletions(-)
diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index c652d740735d..15a2a53e77b0 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -13,11 +13,8 @@ KASAN uses compile-time instrumentation to insert validity checks before every
memory access, and therefore requires a compiler version that supports that.
Generic KASAN is supported in both GCC and Clang. With GCC it requires version
-4.9.2 or later for basic support and version 5.0 or later for detection of
-out-of-bounds accesses for stack and global variables and for inline
-instrumentation mode (see the Usage section). With Clang it requires version
-7.0.0 or later and it doesn't support detection of out-of-bounds accesses for
-global variables yet.
+8.3.0 or later. With Clang it requires version 7.0.0 or later, but detection of
+out-of-bounds accesses for global variables is only supported since Clang 11.
Tag-based KASAN is only supported in Clang and requires version 7.0.0 or later.
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 89053defc0d9..047b53dbfd58 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -40,6 +40,7 @@ choice
software tag-based KASAN (a version based on software memory
tagging, arm64 only, similar to userspace HWASan, enabled with
CONFIG_KASAN_SW_TAGS).
+
Both generic and tag-based KASAN are strictly debugging features.
config KASAN_GENERIC
@@ -51,16 +52,18 @@ config KASAN_GENERIC
select STACKDEPOT
help
Enables generic KASAN mode.
- Supported in both GCC and Clang. With GCC it requires version 4.9.2
- or later for basic support and version 5.0 or later for detection of
- out-of-bounds accesses for stack and global variables and for inline
- instrumentation mode (CONFIG_KASAN_INLINE). With Clang it requires
- version 3.7.0 or later and it doesn't support detection of
- out-of-bounds accesses for global variables yet.
+
+ This mode is supported in both GCC and Clang. With GCC it requires
+ version 8.3.0 or later. With Clang it requires version 7.0.0 or
+ later, but detection of out-of-bounds accesses for global variables
+ is supported only since Clang 11.
+
This mode consumes about 1/8th of available memory at kernel start
and introduces an overhead of ~x1.5 for the rest of the allocations.
The performance slowdown is ~x3.
+
For better error detection enable CONFIG_STACKTRACE.
+
Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB
(the resulting kernel does not boot).
@@ -73,15 +76,19 @@ config KASAN_SW_TAGS
select STACKDEPOT
help
Enables software tag-based KASAN mode.
+
This mode requires Top Byte Ignore support by the CPU and therefore
- is only supported for arm64.
- This mode requires Clang version 7.0.0 or later.
+ is only supported for arm64. This mode requires Clang version 7.0.0
+ or later.
+
This mode consumes about 1/16th of available memory at kernel start
and introduces an overhead of ~20% for the rest of the allocations.
This mode may potentially introduce problems relating to pointer
casting and comparison, as it embeds tags into the top byte of each
pointer.
+
For better error detection enable CONFIG_STACKTRACE.
+
Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB
(the resulting kernel does not boot).
@@ -107,7 +114,6 @@ config KASAN_INLINE
memory accesses. This is faster than outline (in some workloads
it gives about x2 boost over outline instrumentation), but
make kernel's .text size much bigger.
- For CONFIG_KASAN_GENERIC this requires GCC 5.0 or later.
endchoice
--
2.27.0.212.ge8ba1cc988-goog
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH 1/2] kasan: Improve and simplify Kconfig.kasan
2020-06-29 10:41 [PATCH 1/2] kasan: Improve and simplify Kconfig.kasan Marco Elver
2020-06-29 10:41 ` [PATCH 2/2] kasan: Update required compiler versions in documentation Marco Elver
@ 2020-06-29 13:34 ` Andrey Konovalov
1 sibling, 0 replies; 4+ messages in thread
From: Andrey Konovalov @ 2020-06-29 13:34 UTC (permalink / raw)
To: Marco Elver
Cc: Andrew Morton, Dmitry Vyukov, Alexander Potapenko, LKML,
kasan-dev, Andrey Ryabinin, Nick Desaulniers, Walter Wu,
Arnd Bergmann, Daniel Axtens, open list:DOCUMENTATION,
clang-built-linux
On Mon, Jun 29, 2020 at 12:42 PM Marco Elver <elver@google.com> wrote:
>
> Turn 'KASAN' into a menuconfig, to avoid cluttering its parent menu with
> the suboptions if enabled. Use 'if KASAN ... endif' instead of having
> to 'depend on KASAN' for each entry.
>
> Signed-off-by: Marco Elver <elver@google.com>
> ---
> lib/Kconfig.kasan | 15 ++++++++-------
> 1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index 34b84bcbd3d9..89053defc0d9 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -18,7 +18,7 @@ config CC_HAS_KASAN_SW_TAGS
> config CC_HAS_WORKING_NOSANITIZE_ADDRESS
> def_bool !CC_IS_GCC || GCC_VERSION >= 80300
>
> -config KASAN
> +menuconfig KASAN
> bool "KASAN: runtime memory debugger"
> depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
> (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)
> @@ -29,9 +29,10 @@ config KASAN
> designed to find out-of-bounds accesses and use-after-free bugs.
> See Documentation/dev-tools/kasan.rst for details.
>
> +if KASAN
> +
> choice
> prompt "KASAN mode"
> - depends on KASAN
> default KASAN_GENERIC
> help
> KASAN has two modes: generic KASAN (similar to userspace ASan,
> @@ -88,7 +89,6 @@ endchoice
>
> choice
> prompt "Instrumentation type"
> - depends on KASAN
> default KASAN_OUTLINE
>
> config KASAN_OUTLINE
> @@ -113,7 +113,6 @@ endchoice
>
> config KASAN_STACK_ENABLE
> bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
> - depends on KASAN
> help
> The LLVM stack address sanitizer has a know problem that
> causes excessive stack usage in a lot of functions, see
> @@ -134,7 +133,7 @@ config KASAN_STACK
>
> config KASAN_S390_4_LEVEL_PAGING
> bool "KASan: use 4-level paging"
> - depends on KASAN && S390
> + depends on S390
> help
> Compiling the kernel with KASan disables automatic 3-level vs
> 4-level paging selection. 3-level paging is used by default (up
> @@ -151,7 +150,7 @@ config KASAN_SW_TAGS_IDENTIFY
>
> config KASAN_VMALLOC
> bool "Back mappings in vmalloc space with real shadow memory"
> - depends on KASAN && HAVE_ARCH_KASAN_VMALLOC
> + depends on HAVE_ARCH_KASAN_VMALLOC
> help
> By default, the shadow region for vmalloc space is the read-only
> zero page. This means that KASAN cannot detect errors involving
> @@ -164,8 +163,10 @@ config KASAN_VMALLOC
>
> config TEST_KASAN
> tristate "Module for testing KASAN for bug detection"
> - depends on m && KASAN
> + depends on m
> help
> This is a test module doing various nasty things like
> out of bounds accesses, use after free. It is useful for testing
> kernel debugging features like KASAN.
> +
> +endif # KASAN
> --
> 2.27.0.212.ge8ba1cc988-goog
>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH 2/2] kasan: Update required compiler versions in documentation
2020-06-29 10:41 ` [PATCH 2/2] kasan: Update required compiler versions in documentation Marco Elver
@ 2020-06-29 13:36 ` Andrey Konovalov
0 siblings, 0 replies; 4+ messages in thread
From: Andrey Konovalov @ 2020-06-29 13:36 UTC (permalink / raw)
To: Marco Elver
Cc: Andrew Morton, Dmitry Vyukov, Alexander Potapenko, LKML,
kasan-dev, Andrey Ryabinin, Nick Desaulniers, Walter Wu,
Arnd Bergmann, Daniel Axtens, open list:DOCUMENTATION,
clang-built-linux
On Mon, Jun 29, 2020 at 12:42 PM Marco Elver <elver@google.com> wrote:
>
> Updates the recently changed compiler requirements for KASAN. In
> particular, we require GCC >= 8.3.0, and add a note that Clang 11
> supports OOB detection of globals.
>
> Fixes: 7b861a53e46b ("kasan: Bump required compiler version")
> Fixes: acf7b0bf7dcf ("kasan: Fix required compiler version")
> Signed-off-by: Marco Elver <elver@google.com>
> ---
> Documentation/dev-tools/kasan.rst | 7 ++-----
> lib/Kconfig.kasan | 24 +++++++++++++++---------
> 2 files changed, 17 insertions(+), 14 deletions(-)
>
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> index c652d740735d..15a2a53e77b0 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -13,11 +13,8 @@ KASAN uses compile-time instrumentation to insert validity checks before every
> memory access, and therefore requires a compiler version that supports that.
>
> Generic KASAN is supported in both GCC and Clang. With GCC it requires version
> -4.9.2 or later for basic support and version 5.0 or later for detection of
> -out-of-bounds accesses for stack and global variables and for inline
> -instrumentation mode (see the Usage section). With Clang it requires version
> -7.0.0 or later and it doesn't support detection of out-of-bounds accesses for
> -global variables yet.
> +8.3.0 or later. With Clang it requires version 7.0.0 or later, but detection of
> +out-of-bounds accesses for global variables is only supported since Clang 11.
>
> Tag-based KASAN is only supported in Clang and requires version 7.0.0 or later.
>
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index 89053defc0d9..047b53dbfd58 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -40,6 +40,7 @@ choice
> software tag-based KASAN (a version based on software memory
> tagging, arm64 only, similar to userspace HWASan, enabled with
> CONFIG_KASAN_SW_TAGS).
> +
> Both generic and tag-based KASAN are strictly debugging features.
>
> config KASAN_GENERIC
> @@ -51,16 +52,18 @@ config KASAN_GENERIC
> select STACKDEPOT
> help
> Enables generic KASAN mode.
> - Supported in both GCC and Clang. With GCC it requires version 4.9.2
> - or later for basic support and version 5.0 or later for detection of
> - out-of-bounds accesses for stack and global variables and for inline
> - instrumentation mode (CONFIG_KASAN_INLINE). With Clang it requires
> - version 3.7.0 or later and it doesn't support detection of
> - out-of-bounds accesses for global variables yet.
> +
> + This mode is supported in both GCC and Clang. With GCC it requires
> + version 8.3.0 or later. With Clang it requires version 7.0.0 or
> + later, but detection of out-of-bounds accesses for global variables
> + is supported only since Clang 11.
> +
> This mode consumes about 1/8th of available memory at kernel start
> and introduces an overhead of ~x1.5 for the rest of the allocations.
> The performance slowdown is ~x3.
> +
> For better error detection enable CONFIG_STACKTRACE.
> +
> Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB
> (the resulting kernel does not boot).
>
> @@ -73,15 +76,19 @@ config KASAN_SW_TAGS
> select STACKDEPOT
> help
> Enables software tag-based KASAN mode.
> +
> This mode requires Top Byte Ignore support by the CPU and therefore
> - is only supported for arm64.
> - This mode requires Clang version 7.0.0 or later.
> + is only supported for arm64. This mode requires Clang version 7.0.0
> + or later.
> +
> This mode consumes about 1/16th of available memory at kernel start
> and introduces an overhead of ~20% for the rest of the allocations.
> This mode may potentially introduce problems relating to pointer
> casting and comparison, as it embeds tags into the top byte of each
> pointer.
> +
> For better error detection enable CONFIG_STACKTRACE.
> +
> Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB
> (the resulting kernel does not boot).
>
> @@ -107,7 +114,6 @@ config KASAN_INLINE
> memory accesses. This is faster than outline (in some workloads
> it gives about x2 boost over outline instrumentation), but
> make kernel's .text size much bigger.
> - For CONFIG_KASAN_GENERIC this requires GCC 5.0 or later.
>
> endchoice
>
> --
> 2.27.0.212.ge8ba1cc988-goog
>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Thanks!
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-06-29 20:57 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-06-29 10:41 [PATCH 1/2] kasan: Improve and simplify Kconfig.kasan Marco Elver
2020-06-29 10:41 ` [PATCH 2/2] kasan: Update required compiler versions in documentation Marco Elver
2020-06-29 13:36 ` Andrey Konovalov
2020-06-29 13:34 ` [PATCH 1/2] kasan: Improve and simplify Kconfig.kasan Andrey Konovalov
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.