LinuxLists.cc - [PATCH v3] kasan: remove redundant config option

2021-01-08 04:12:00

Subject: [PATCH v3] kasan: remove redundant config option

CONFIG_KASAN_STACK and CONFIG_KASAN_STACK_ENABLE both enable KASAN stack
instrumentation, but we should only need one config, so that we remove
CONFIG_KASAN_STACK_ENABLE and make CONFIG_KASAN_STACK workable. see [1].

When enable KASAN stack instrumentation, then for gcc we could do
no prompt and default value y, and for clang prompt and default
value n.

[1]: https://bugzilla.kernel.org/show_bug.cgi?id=210221

Signed-off-by: Walter Wu <[email protected]>
Suggested-by: Dmitry Vyukov <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Nathan Chancellor <[email protected]>
---

v2: make commit log to be more readable.
v3: remain CONFIG_KASAN_STACK_ENABLE setting
fix the pre-processors syntax

---
arch/arm64/kernel/sleep.S | 2 +-
arch/x86/kernel/acpi/wakeup_64.S | 2 +-
include/linux/kasan.h | 2 +-
lib/Kconfig.kasan | 8 ++------
mm/kasan/common.c | 2 +-
mm/kasan/kasan.h | 2 +-
mm/kasan/report_generic.c | 2 +-
scripts/Makefile.kasan | 10 ++++++++--
8 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
index 6bdef7362c0e..7c44ede122a9 100644
--- a/arch/arm64/kernel/sleep.S
+++ b/arch/arm64/kernel/sleep.S
@@ -133,7 +133,7 @@ SYM_FUNC_START(_cpu_resume)
*/
bl cpu_do_resume

-#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
+#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
mov x0, sp
bl kasan_unpoison_task_stack_below
#endif
diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
index 5d3a0b8fd379..c7f412f4e07d 100644
--- a/arch/x86/kernel/acpi/wakeup_64.S
+++ b/arch/x86/kernel/acpi/wakeup_64.S
@@ -112,7 +112,7 @@ SYM_FUNC_START(do_suspend_lowlevel)
movq pt_regs_r14(%rax), %r14
movq pt_regs_r15(%rax), %r15

-#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
+#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
/*
* The suspend path may have poisoned some areas deeper in the stack,
* which we now need to unpoison.
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 5e0655fb2a6f..35d1e9b2cbfa 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -302,7 +302,7 @@ static inline void kasan_kfree_large(void *ptr, unsigned long ip) {}

#endif /* CONFIG_KASAN */

-#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
+#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
void kasan_unpoison_task_stack(struct task_struct *task);
#else
static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index f5fa4ba126bf..fde82ec85f8f 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -138,9 +138,10 @@ config KASAN_INLINE

endchoice

-config KASAN_STACK_ENABLE
+config KASAN_STACK
bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
depends on KASAN_GENERIC || KASAN_SW_TAGS
+ default y if CC_IS_GCC
help
The LLVM stack address sanitizer has a know problem that
causes excessive stack usage in a lot of functions, see
@@ -154,11 +155,6 @@ config KASAN_STACK_ENABLE
CONFIG_COMPILE_TEST. On gcc it is assumed to always be safe
to use and enabled by default.

-config KASAN_STACK
- int
- default 1 if KASAN_STACK_ENABLE || CC_IS_GCC
- default 0
-
config KASAN_SW_TAGS_IDENTIFY
bool "Enable memory corruption identification"
depends on KASAN_SW_TAGS
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 38ba2aecd8f4..bf8b073eed62 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -63,7 +63,7 @@ void __kasan_unpoison_range(const void *address, size_t size)
unpoison_range(address, size);
}

-#if CONFIG_KASAN_STACK
+#ifdef CONFIG_KASAN_STACK
/* Unpoison the entire stack for a task. */
void kasan_unpoison_task_stack(struct task_struct *task)
{
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index cc4d9e1d49b1..bdfdb1cff653 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -224,7 +224,7 @@ void *find_first_bad_addr(void *addr, size_t size);
const char *get_bug_type(struct kasan_access_info *info);
void metadata_fetch_row(char *buffer, void *row);

-#if defined(CONFIG_KASAN_GENERIC) && CONFIG_KASAN_STACK
+#if defined(CONFIG_KASAN_GENERIC) && defined(CONFIG_KASAN_STACK)
void print_address_stack_frame(const void *addr);
#else
static inline void print_address_stack_frame(const void *addr) { }
diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c
index 8a9c889872da..4e16518d9877 100644
--- a/mm/kasan/report_generic.c
+++ b/mm/kasan/report_generic.c
@@ -128,7 +128,7 @@ void metadata_fetch_row(char *buffer, void *row)
memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
}

-#if CONFIG_KASAN_STACK
+#ifdef CONFIG_KASAN_STACK
static bool __must_check tokenize_frame_descr(const char **frame_descr,
char *token, size_t max_tok_len,
unsigned long *value)
diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index 1e000cc2e7b4..abf231d209b1 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -2,6 +2,12 @@
CFLAGS_KASAN_NOSANITIZE := -fno-builtin
KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)

+ifdef CONFIG_KASAN_STACK
+ stack_enable := 1
+else
+ stack_enable := 0
+endif
+
ifdef CONFIG_KASAN_GENERIC

ifdef CONFIG_KASAN_INLINE
@@ -27,7 +33,7 @@ else
CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
$(call cc-param,asan-globals=1) \
$(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
- $(call cc-param,asan-stack=$(CONFIG_KASAN_STACK)) \
+ $(call cc-param,asan-stack=$(stack_enable)) \
$(call cc-param,asan-instrument-allocas=1)
endif

@@ -42,7 +48,7 @@ else
endif

CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
- -mllvm -hwasan-instrument-stack=$(CONFIG_KASAN_STACK) \
+ -mllvm -hwasan-instrument-stack=$(stack_enable) \
-mllvm -hwasan-use-short-granules=0 \
$(instrumentation_flags)

--
2.18.0

2021-01-08 04:19:41

by Nathan Chancellor

[permalink] [raw]

Subject: Re: [PATCH v3] kasan: remove redundant config option

On Fri, Jan 08, 2021 at 12:09:40PM +0800, Walter Wu wrote:
> CONFIG_KASAN_STACK and CONFIG_KASAN_STACK_ENABLE both enable KASAN stack
> instrumentation, but we should only need one config, so that we remove
> CONFIG_KASAN_STACK_ENABLE and make CONFIG_KASAN_STACK workable. see [1].
>
> When enable KASAN stack instrumentation, then for gcc we could do
> no prompt and default value y, and for clang prompt and default
> value n.
>
> [1]: https://bugzilla.kernel.org/show_bug.cgi?id=210221
>
> Signed-off-by: Walter Wu <[email protected]>
> Suggested-by: Dmitry Vyukov <[email protected]>
> Cc: Andrey Ryabinin <[email protected]>
> Cc: Dmitry Vyukov <[email protected]>
> Cc: Andrey Konovalov <[email protected]>
> Cc: Alexander Potapenko <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Nathan Chancellor <[email protected]>

Reviewed-by: Nathan Chancellor <[email protected]>

> ---
>
> v2: make commit log to be more readable.
> v3: remain CONFIG_KASAN_STACK_ENABLE setting
> fix the pre-processors syntax
>
> ---
> arch/arm64/kernel/sleep.S | 2 +-
> arch/x86/kernel/acpi/wakeup_64.S | 2 +-
> include/linux/kasan.h | 2 +-
> lib/Kconfig.kasan | 8 ++------
> mm/kasan/common.c | 2 +-
> mm/kasan/kasan.h | 2 +-
> mm/kasan/report_generic.c | 2 +-
> scripts/Makefile.kasan | 10 ++++++++--
> 8 files changed, 16 insertions(+), 14 deletions(-)
>
> diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
> index 6bdef7362c0e..7c44ede122a9 100644
> --- a/arch/arm64/kernel/sleep.S
> +++ b/arch/arm64/kernel/sleep.S
> @@ -133,7 +133,7 @@ SYM_FUNC_START(_cpu_resume)
> */
> bl cpu_do_resume
>
> -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> mov x0, sp
> bl kasan_unpoison_task_stack_below
> #endif
> diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
> index 5d3a0b8fd379..c7f412f4e07d 100644
> --- a/arch/x86/kernel/acpi/wakeup_64.S
> +++ b/arch/x86/kernel/acpi/wakeup_64.S
> @@ -112,7 +112,7 @@ SYM_FUNC_START(do_suspend_lowlevel)
> movq pt_regs_r14(%rax), %r14
> movq pt_regs_r15(%rax), %r15
>
> -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> /*
> * The suspend path may have poisoned some areas deeper in the stack,
> * which we now need to unpoison.
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 5e0655fb2a6f..35d1e9b2cbfa 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -302,7 +302,7 @@ static inline void kasan_kfree_large(void *ptr, unsigned long ip) {}
>
> #endif /* CONFIG_KASAN */
>
> -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> void kasan_unpoison_task_stack(struct task_struct *task);
> #else
> static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index f5fa4ba126bf..fde82ec85f8f 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -138,9 +138,10 @@ config KASAN_INLINE
>
> endchoice
>
> -config KASAN_STACK_ENABLE
> +config KASAN_STACK
> bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
> depends on KASAN_GENERIC || KASAN_SW_TAGS
> + default y if CC_IS_GCC
> help
> The LLVM stack address sanitizer has a know problem that
> causes excessive stack usage in a lot of functions, see
> @@ -154,11 +155,6 @@ config KASAN_STACK_ENABLE
> CONFIG_COMPILE_TEST. On gcc it is assumed to always be safe
> to use and enabled by default.
>
> -config KASAN_STACK
> - int
> - default 1 if KASAN_STACK_ENABLE || CC_IS_GCC
> - default 0
> -
> config KASAN_SW_TAGS_IDENTIFY
> bool "Enable memory corruption identification"
> depends on KASAN_SW_TAGS
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 38ba2aecd8f4..bf8b073eed62 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -63,7 +63,7 @@ void __kasan_unpoison_range(const void *address, size_t size)
> unpoison_range(address, size);
> }
>
> -#if CONFIG_KASAN_STACK
> +#ifdef CONFIG_KASAN_STACK
> /* Unpoison the entire stack for a task. */
> void kasan_unpoison_task_stack(struct task_struct *task)
> {
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index cc4d9e1d49b1..bdfdb1cff653 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -224,7 +224,7 @@ void *find_first_bad_addr(void *addr, size_t size);
> const char *get_bug_type(struct kasan_access_info *info);
> void metadata_fetch_row(char *buffer, void *row);
>
> -#if defined(CONFIG_KASAN_GENERIC) && CONFIG_KASAN_STACK
> +#if defined(CONFIG_KASAN_GENERIC) && defined(CONFIG_KASAN_STACK)
> void print_address_stack_frame(const void *addr);
> #else
> static inline void print_address_stack_frame(const void *addr) { }
> diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c
> index 8a9c889872da..4e16518d9877 100644
> --- a/mm/kasan/report_generic.c
> +++ b/mm/kasan/report_generic.c
> @@ -128,7 +128,7 @@ void metadata_fetch_row(char *buffer, void *row)
> memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
> }
>
> -#if CONFIG_KASAN_STACK
> +#ifdef CONFIG_KASAN_STACK
> static bool __must_check tokenize_frame_descr(const char **frame_descr,
> char *token, size_t max_tok_len,
> unsigned long *value)
> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index 1e000cc2e7b4..abf231d209b1 100644
> --- a/scripts/Makefile.kasan
> +++ b/scripts/Makefile.kasan
> @@ -2,6 +2,12 @@
> CFLAGS_KASAN_NOSANITIZE := -fno-builtin
> KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
>
> +ifdef CONFIG_KASAN_STACK
> + stack_enable := 1
> +else
> + stack_enable := 0
> +endif
> +
> ifdef CONFIG_KASAN_GENERIC
>
> ifdef CONFIG_KASAN_INLINE
> @@ -27,7 +33,7 @@ else
> CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
> $(call cc-param,asan-globals=1) \
> $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
> - $(call cc-param,asan-stack=$(CONFIG_KASAN_STACK)) \
> + $(call cc-param,asan-stack=$(stack_enable)) \
> $(call cc-param,asan-instrument-allocas=1)
> endif
>
> @@ -42,7 +48,7 @@ else
> endif
>
> CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
> - -mllvm -hwasan-instrument-stack=$(CONFIG_KASAN_STACK) \
> + -mllvm -hwasan-instrument-stack=$(stack_enable) \
> -mllvm -hwasan-use-short-granules=0 \
> $(instrumentation_flags)
>
> --
> 2.18.0
>

2021-01-08 19:01:14

by Andrey Konovalov

[permalink] [raw]

Subject: Re: [PATCH v3] kasan: remove redundant config option

On Fri, Jan 8, 2021 at 5:09 AM Walter Wu <[email protected]> wrote:
>
> CONFIG_KASAN_STACK and CONFIG_KASAN_STACK_ENABLE both enable KASAN stack
> instrumentation, but we should only need one config, so that we remove
> CONFIG_KASAN_STACK_ENABLE and make CONFIG_KASAN_STACK workable. see [1].
>
> When enable KASAN stack instrumentation, then for gcc we could do
> no prompt and default value y, and for clang prompt and default
> value n.
>
> [1]: https://bugzilla.kernel.org/show_bug.cgi?id=210221
>
> Signed-off-by: Walter Wu <[email protected]>
> Suggested-by: Dmitry Vyukov <[email protected]>
> Cc: Andrey Ryabinin <[email protected]>
> Cc: Dmitry Vyukov <[email protected]>
> Cc: Andrey Konovalov <[email protected]>
> Cc: Alexander Potapenko <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Nathan Chancellor <[email protected]>
> ---
>
> v2: make commit log to be more readable.
> v3: remain CONFIG_KASAN_STACK_ENABLE setting
> fix the pre-processors syntax
>
> ---
> arch/arm64/kernel/sleep.S | 2 +-
> arch/x86/kernel/acpi/wakeup_64.S | 2 +-
> include/linux/kasan.h | 2 +-
> lib/Kconfig.kasan | 8 ++------
> mm/kasan/common.c | 2 +-
> mm/kasan/kasan.h | 2 +-
> mm/kasan/report_generic.c | 2 +-
> scripts/Makefile.kasan | 10 ++++++++--
> 8 files changed, 16 insertions(+), 14 deletions(-)
>
> diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
> index 6bdef7362c0e..7c44ede122a9 100644
> --- a/arch/arm64/kernel/sleep.S
> +++ b/arch/arm64/kernel/sleep.S
> @@ -133,7 +133,7 @@ SYM_FUNC_START(_cpu_resume)
> */
> bl cpu_do_resume
>
> -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> mov x0, sp
> bl kasan_unpoison_task_stack_below
> #endif
> diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
> index 5d3a0b8fd379..c7f412f4e07d 100644
> --- a/arch/x86/kernel/acpi/wakeup_64.S
> +++ b/arch/x86/kernel/acpi/wakeup_64.S
> @@ -112,7 +112,7 @@ SYM_FUNC_START(do_suspend_lowlevel)
> movq pt_regs_r14(%rax), %r14
> movq pt_regs_r15(%rax), %r15
>
> -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> /*
> * The suspend path may have poisoned some areas deeper in the stack,
> * which we now need to unpoison.
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 5e0655fb2a6f..35d1e9b2cbfa 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -302,7 +302,7 @@ static inline void kasan_kfree_large(void *ptr, unsigned long ip) {}
>
> #endif /* CONFIG_KASAN */
>
> -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> void kasan_unpoison_task_stack(struct task_struct *task);
> #else
> static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index f5fa4ba126bf..fde82ec85f8f 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -138,9 +138,10 @@ config KASAN_INLINE
>
> endchoice
>
> -config KASAN_STACK_ENABLE
> +config KASAN_STACK
> bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
> depends on KASAN_GENERIC || KASAN_SW_TAGS
> + default y if CC_IS_GCC
> help
> The LLVM stack address sanitizer has a know problem that
> causes excessive stack usage in a lot of functions, see
> @@ -154,11 +155,6 @@ config KASAN_STACK_ENABLE
> CONFIG_COMPILE_TEST. On gcc it is assumed to always be safe
> to use and enabled by default.
>
> -config KASAN_STACK
> - int
> - default 1 if KASAN_STACK_ENABLE || CC_IS_GCC
> - default 0
> -
> config KASAN_SW_TAGS_IDENTIFY
> bool "Enable memory corruption identification"
> depends on KASAN_SW_TAGS
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 38ba2aecd8f4..bf8b073eed62 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -63,7 +63,7 @@ void __kasan_unpoison_range(const void *address, size_t size)
> unpoison_range(address, size);
> }
>
> -#if CONFIG_KASAN_STACK
> +#ifdef CONFIG_KASAN_STACK
> /* Unpoison the entire stack for a task. */
> void kasan_unpoison_task_stack(struct task_struct *task)
> {
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index cc4d9e1d49b1..bdfdb1cff653 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -224,7 +224,7 @@ void *find_first_bad_addr(void *addr, size_t size);
> const char *get_bug_type(struct kasan_access_info *info);
> void metadata_fetch_row(char *buffer, void *row);
>
> -#if defined(CONFIG_KASAN_GENERIC) && CONFIG_KASAN_STACK
> +#if defined(CONFIG_KASAN_GENERIC) && defined(CONFIG_KASAN_STACK)
> void print_address_stack_frame(const void *addr);
> #else
> static inline void print_address_stack_frame(const void *addr) { }
> diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c
> index 8a9c889872da..4e16518d9877 100644
> --- a/mm/kasan/report_generic.c
> +++ b/mm/kasan/report_generic.c
> @@ -128,7 +128,7 @@ void metadata_fetch_row(char *buffer, void *row)
> memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
> }
>
> -#if CONFIG_KASAN_STACK
> +#ifdef CONFIG_KASAN_STACK
> static bool __must_check tokenize_frame_descr(const char **frame_descr,
> char *token, size_t max_tok_len,
> unsigned long *value)
> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index 1e000cc2e7b4..abf231d209b1 100644
> --- a/scripts/Makefile.kasan
> +++ b/scripts/Makefile.kasan
> @@ -2,6 +2,12 @@
> CFLAGS_KASAN_NOSANITIZE := -fno-builtin
> KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
>
> +ifdef CONFIG_KASAN_STACK
> + stack_enable := 1
> +else
> + stack_enable := 0
> +endif
> +
> ifdef CONFIG_KASAN_GENERIC
>
> ifdef CONFIG_KASAN_INLINE
> @@ -27,7 +33,7 @@ else
> CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
> $(call cc-param,asan-globals=1) \
> $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
> - $(call cc-param,asan-stack=$(CONFIG_KASAN_STACK)) \
> + $(call cc-param,asan-stack=$(stack_enable)) \
> $(call cc-param,asan-instrument-allocas=1)
> endif
>
> @@ -42,7 +48,7 @@ else
> endif
>
> CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
> - -mllvm -hwasan-instrument-stack=$(CONFIG_KASAN_STACK) \
> + -mllvm -hwasan-instrument-stack=$(stack_enable) \
> -mllvm -hwasan-use-short-granules=0 \
> $(instrumentation_flags)
>
> --
> 2.18.0

AFAIR, Arnd wanted to avoid having KASAN_STACK to be enabled by
default when compiling with Clang, since Clang instrumentation leads
to very large kernel stacks, which, in turn, lead to compile-time
warnings. What I don't remember is why there are two configs.

Arnd, is that correct? What was the reason behind having two configs?

2021-01-08 20:33:53

by Arnd Bergmann

[permalink] [raw]

Subject: Re: [PATCH v3] kasan: remove redundant config option

On Fri, Jan 8, 2021 at 7:56 PM Andrey Konovalov <[email protected]> wrote:
> On Fri, Jan 8, 2021 at 5:09 AM Walter Wu <[email protected]> wrote:

> > @@ -2,6 +2,12 @@
> > CFLAGS_KASAN_NOSANITIZE := -fno-builtin
> > KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
> >
> > +ifdef CONFIG_KASAN_STACK
> > + stack_enable := 1
> > +else
> > + stack_enable := 0
> > +endif
> > +
>
> AFAIR, Arnd wanted to avoid having KASAN_STACK to be enabled by
> default when compiling with Clang, since Clang instrumentation leads
> to very large kernel stacks, which, in turn, lead to compile-time
> warnings. What I don't remember is why there are two configs.
>
> Arnd, is that correct? What was the reason behind having two configs?

I think I just considered it cleaner than defining the extra variable in the
Makefile at the time, as this was the only place that referenced
CONFIG_KASAN_STACK.

The '#if CONFIG_KASAN_STACK' (rather than #ifdef) that got added
later do make my version more confusing though, so I agree that
Walter's second patch improves it.

Acked-by: Arnd Bergmann <[email protected]>

On a related note: do you have any hope that clang will ever fix
https://bugs.llvm.org/show_bug.cgi?id=38809 and KASAN_STACK
can be enabled by default on clang without risking stack
overflows?

Arnd

2021-01-11 17:44:17

by Andrey Konovalov

[permalink] [raw]

Subject: Re: [PATCH v3] kasan: remove redundant config option

On Fri, Jan 8, 2021 at 9:31 PM Arnd Bergmann <[email protected]> wrote:
>
> On Fri, Jan 8, 2021 at 7:56 PM Andrey Konovalov <[email protected]> wrote:
> > On Fri, Jan 8, 2021 at 5:09 AM Walter Wu <[email protected]> wrote:
>
> > > @@ -2,6 +2,12 @@
> > > CFLAGS_KASAN_NOSANITIZE := -fno-builtin
> > > KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
> > >
> > > +ifdef CONFIG_KASAN_STACK
> > > + stack_enable := 1
> > > +else
> > > + stack_enable := 0
> > > +endif
> > > +
> >
> > AFAIR, Arnd wanted to avoid having KASAN_STACK to be enabled by
> > default when compiling with Clang, since Clang instrumentation leads
> > to very large kernel stacks, which, in turn, lead to compile-time
> > warnings. What I don't remember is why there are two configs.
> >
> > Arnd, is that correct? What was the reason behind having two configs?
>
> I think I just considered it cleaner than defining the extra variable in the
> Makefile at the time, as this was the only place that referenced
> CONFIG_KASAN_STACK.
>
> The '#if CONFIG_KASAN_STACK' (rather than #ifdef) that got added
> later do make my version more confusing though, so I agree that
> Walter's second patch improves it.
>
> Acked-by: Arnd Bergmann <[email protected]>

Got it, thanks!

> On a related note: do you have any hope that clang will ever fix
> https://bugs.llvm.org/show_bug.cgi?id=38809 and KASAN_STACK
> can be enabled by default on clang without risking stack
> overflows?

Not sure :(

I've filed this on KASAN bugzilla to not forget:
https://bugzilla.kernel.org/show_bug.cgi?id=211139

2021-01-11 17:54:46

by Andrey Konovalov

[permalink] [raw]

Subject: Re: [PATCH v3] kasan: remove redundant config option

On Fri, Jan 8, 2021 at 5:09 AM Walter Wu <[email protected]> wrote:
>
> CONFIG_KASAN_STACK and CONFIG_KASAN_STACK_ENABLE both enable KASAN stack
> instrumentation, but we should only need one config, so that we remove
> CONFIG_KASAN_STACK_ENABLE and make CONFIG_KASAN_STACK workable. see [1].
>
> When enable KASAN stack instrumentation, then for gcc we could do
> no prompt and default value y, and for clang prompt and default
> value n.
>
> [1]: https://bugzilla.kernel.org/show_bug.cgi?id=210221
>
> Signed-off-by: Walter Wu <[email protected]>
> Suggested-by: Dmitry Vyukov <[email protected]>
> Cc: Andrey Ryabinin <[email protected]>
> Cc: Dmitry Vyukov <[email protected]>
> Cc: Andrey Konovalov <[email protected]>
> Cc: Alexander Potapenko <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Nathan Chancellor <[email protected]>
> ---
>
> v2: make commit log to be more readable.
> v3: remain CONFIG_KASAN_STACK_ENABLE setting
> fix the pre-processors syntax
>
> ---
> arch/arm64/kernel/sleep.S | 2 +-
> arch/x86/kernel/acpi/wakeup_64.S | 2 +-
> include/linux/kasan.h | 2 +-
> lib/Kconfig.kasan | 8 ++------
> mm/kasan/common.c | 2 +-
> mm/kasan/kasan.h | 2 +-
> mm/kasan/report_generic.c | 2 +-
> scripts/Makefile.kasan | 10 ++++++++--
> 8 files changed, 16 insertions(+), 14 deletions(-)
>
> diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
> index 6bdef7362c0e..7c44ede122a9 100644
> --- a/arch/arm64/kernel/sleep.S
> +++ b/arch/arm64/kernel/sleep.S
> @@ -133,7 +133,7 @@ SYM_FUNC_START(_cpu_resume)
> */
> bl cpu_do_resume
>
> -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> mov x0, sp
> bl kasan_unpoison_task_stack_below
> #endif
> diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
> index 5d3a0b8fd379..c7f412f4e07d 100644
> --- a/arch/x86/kernel/acpi/wakeup_64.S
> +++ b/arch/x86/kernel/acpi/wakeup_64.S
> @@ -112,7 +112,7 @@ SYM_FUNC_START(do_suspend_lowlevel)
> movq pt_regs_r14(%rax), %r14
> movq pt_regs_r15(%rax), %r15
>
> -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> /*
> * The suspend path may have poisoned some areas deeper in the stack,
> * which we now need to unpoison.
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 5e0655fb2a6f..35d1e9b2cbfa 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -302,7 +302,7 @@ static inline void kasan_kfree_large(void *ptr, unsigned long ip) {}
>
> #endif /* CONFIG_KASAN */
>
> -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> void kasan_unpoison_task_stack(struct task_struct *task);
> #else
> static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index f5fa4ba126bf..fde82ec85f8f 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -138,9 +138,10 @@ config KASAN_INLINE
>
> endchoice
>
> -config KASAN_STACK_ENABLE
> +config KASAN_STACK
> bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST

Does this syntax mean that KASAN_STACK is only present for
CC_IS_CLANG? Or that it can only be disabled for CC_IS_CLANG?

Anyway, I think it's better to 1. allow to control KASAN_STACK
regardless of the compiler (as it was possible before), and 2. avoid
this "bool ... if ..." syntax as it's confusing.

> depends on KASAN_GENERIC || KASAN_SW_TAGS
> + default y if CC_IS_GCC
> help
> The LLVM stack address sanitizer has a know problem that
> causes excessive stack usage in a lot of functions, see
> @@ -154,11 +155,6 @@ config KASAN_STACK_ENABLE
> CONFIG_COMPILE_TEST. On gcc it is assumed to always be safe
> to use and enabled by default.
>
> -config KASAN_STACK
> - int
> - default 1 if KASAN_STACK_ENABLE || CC_IS_GCC
> - default 0
> -
> config KASAN_SW_TAGS_IDENTIFY
> bool "Enable memory corruption identification"
> depends on KASAN_SW_TAGS
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 38ba2aecd8f4..bf8b073eed62 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -63,7 +63,7 @@ void __kasan_unpoison_range(const void *address, size_t size)
> unpoison_range(address, size);
> }
>
> -#if CONFIG_KASAN_STACK
> +#ifdef CONFIG_KASAN_STACK
> /* Unpoison the entire stack for a task. */
> void kasan_unpoison_task_stack(struct task_struct *task)
> {
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index cc4d9e1d49b1..bdfdb1cff653 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -224,7 +224,7 @@ void *find_first_bad_addr(void *addr, size_t size);
> const char *get_bug_type(struct kasan_access_info *info);
> void metadata_fetch_row(char *buffer, void *row);
>
> -#if defined(CONFIG_KASAN_GENERIC) && CONFIG_KASAN_STACK
> +#if defined(CONFIG_KASAN_GENERIC) && defined(CONFIG_KASAN_STACK)
> void print_address_stack_frame(const void *addr);
> #else
> static inline void print_address_stack_frame(const void *addr) { }
> diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c
> index 8a9c889872da..4e16518d9877 100644
> --- a/mm/kasan/report_generic.c
> +++ b/mm/kasan/report_generic.c
> @@ -128,7 +128,7 @@ void metadata_fetch_row(char *buffer, void *row)
> memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
> }
>
> -#if CONFIG_KASAN_STACK
> +#ifdef CONFIG_KASAN_STACK
> static bool __must_check tokenize_frame_descr(const char **frame_descr,
> char *token, size_t max_tok_len,
> unsigned long *value)
> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index 1e000cc2e7b4..abf231d209b1 100644
> --- a/scripts/Makefile.kasan
> +++ b/scripts/Makefile.kasan
> @@ -2,6 +2,12 @@
> CFLAGS_KASAN_NOSANITIZE := -fno-builtin
> KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
>
> +ifdef CONFIG_KASAN_STACK
> + stack_enable := 1
> +else
> + stack_enable := 0
> +endif
> +
> ifdef CONFIG_KASAN_GENERIC
>
> ifdef CONFIG_KASAN_INLINE
> @@ -27,7 +33,7 @@ else
> CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
> $(call cc-param,asan-globals=1) \
> $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
> - $(call cc-param,asan-stack=$(CONFIG_KASAN_STACK)) \
> + $(call cc-param,asan-stack=$(stack_enable)) \
> $(call cc-param,asan-instrument-allocas=1)
> endif
>
> @@ -42,7 +48,7 @@ else
> endif
>
> CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
> - -mllvm -hwasan-instrument-stack=$(CONFIG_KASAN_STACK) \
> + -mllvm -hwasan-instrument-stack=$(stack_enable) \
> -mllvm -hwasan-use-short-granules=0 \
> $(instrumentation_flags)
>
> --
> 2.18.0
>
> --
> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20210108040940.1138-1-walter-zh.wu%40mediatek.com.

2021-01-11 19:02:20

by Nathan Chancellor

[permalink] [raw]

Subject: Re: [PATCH v3] kasan: remove redundant config option

On Mon, Jan 11, 2021 at 06:49:37PM +0100, Andrey Konovalov wrote:
> On Fri, Jan 8, 2021 at 5:09 AM Walter Wu <[email protected]> wrote:
> >
> > CONFIG_KASAN_STACK and CONFIG_KASAN_STACK_ENABLE both enable KASAN stack
> > instrumentation, but we should only need one config, so that we remove
> > CONFIG_KASAN_STACK_ENABLE and make CONFIG_KASAN_STACK workable. see [1].
> >
> > When enable KASAN stack instrumentation, then for gcc we could do
> > no prompt and default value y, and for clang prompt and default
> > value n.
> >
> > [1]: https://bugzilla.kernel.org/show_bug.cgi?id=210221
> >
> > Signed-off-by: Walter Wu <[email protected]>
> > Suggested-by: Dmitry Vyukov <[email protected]>
> > Cc: Andrey Ryabinin <[email protected]>
> > Cc: Dmitry Vyukov <[email protected]>
> > Cc: Andrey Konovalov <[email protected]>
> > Cc: Alexander Potapenko <[email protected]>
> > Cc: Andrew Morton <[email protected]>
> > Cc: Nathan Chancellor <[email protected]>
> > ---
> >
> > v2: make commit log to be more readable.
> > v3: remain CONFIG_KASAN_STACK_ENABLE setting
> > fix the pre-processors syntax
> >
> > ---
> > arch/arm64/kernel/sleep.S | 2 +-
> > arch/x86/kernel/acpi/wakeup_64.S | 2 +-
> > include/linux/kasan.h | 2 +-
> > lib/Kconfig.kasan | 8 ++------
> > mm/kasan/common.c | 2 +-
> > mm/kasan/kasan.h | 2 +-
> > mm/kasan/report_generic.c | 2 +-
> > scripts/Makefile.kasan | 10 ++++++++--
> > 8 files changed, 16 insertions(+), 14 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
> > index 6bdef7362c0e..7c44ede122a9 100644
> > --- a/arch/arm64/kernel/sleep.S
> > +++ b/arch/arm64/kernel/sleep.S
> > @@ -133,7 +133,7 @@ SYM_FUNC_START(_cpu_resume)
> > */
> > bl cpu_do_resume
> >
> > -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> > +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> > mov x0, sp
> > bl kasan_unpoison_task_stack_below
> > #endif
> > diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
> > index 5d3a0b8fd379..c7f412f4e07d 100644
> > --- a/arch/x86/kernel/acpi/wakeup_64.S
> > +++ b/arch/x86/kernel/acpi/wakeup_64.S
> > @@ -112,7 +112,7 @@ SYM_FUNC_START(do_suspend_lowlevel)
> > movq pt_regs_r14(%rax), %r14
> > movq pt_regs_r15(%rax), %r15
> >
> > -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> > +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> > /*
> > * The suspend path may have poisoned some areas deeper in the stack,
> > * which we now need to unpoison.
> > diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> > index 5e0655fb2a6f..35d1e9b2cbfa 100644
> > --- a/include/linux/kasan.h
> > +++ b/include/linux/kasan.h
> > @@ -302,7 +302,7 @@ static inline void kasan_kfree_large(void *ptr, unsigned long ip) {}
> >
> > #endif /* CONFIG_KASAN */
> >
> > -#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> > +#if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> > void kasan_unpoison_task_stack(struct task_struct *task);
> > #else
> > static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
> > diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> > index f5fa4ba126bf..fde82ec85f8f 100644
> > --- a/lib/Kconfig.kasan
> > +++ b/lib/Kconfig.kasan
> > @@ -138,9 +138,10 @@ config KASAN_INLINE
> >
> > endchoice
> >
> > -config KASAN_STACK_ENABLE
> > +config KASAN_STACK
> > bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
>
> Does this syntax mean that KASAN_STACK is only present for
> CC_IS_CLANG? Or that it can only be disabled for CC_IS_CLANG?

It means that the option can only be disabled for clang.

> Anyway, I think it's better to 1. allow to control KASAN_STACK
> regardless of the compiler (as it was possible before), and 2. avoid

It has never been possible to control KASAN_STACK for GCC because of the
bool ... if ... syntax. This patch does not change that logic. Making it
possible to control KASAN_STACK with GCC seems fine but that is going to
be a new change that would probably be suited for a new patch on top of
this one.

> this "bool ... if ..." syntax as it's confusing.
>
> > depends on KASAN_GENERIC || KASAN_SW_TAGS
> > + default y if CC_IS_GCC
> > help
> > The LLVM stack address sanitizer has a know problem that
> > causes excessive stack usage in a lot of functions, see
> > @@ -154,11 +155,6 @@ config KASAN_STACK_ENABLE
> > CONFIG_COMPILE_TEST. On gcc it is assumed to always be safe
> > to use and enabled by default.
> >
> > -config KASAN_STACK
> > - int
> > - default 1 if KASAN_STACK_ENABLE || CC_IS_GCC
> > - default 0
> > -
> > config KASAN_SW_TAGS_IDENTIFY
> > bool "Enable memory corruption identification"
> > depends on KASAN_SW_TAGS
> > diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> > index 38ba2aecd8f4..bf8b073eed62 100644
> > --- a/mm/kasan/common.c
> > +++ b/mm/kasan/common.c
> > @@ -63,7 +63,7 @@ void __kasan_unpoison_range(const void *address, size_t size)
> > unpoison_range(address, size);
> > }
> >
> > -#if CONFIG_KASAN_STACK
> > +#ifdef CONFIG_KASAN_STACK
> > /* Unpoison the entire stack for a task. */
> > void kasan_unpoison_task_stack(struct task_struct *task)
> > {
> > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> > index cc4d9e1d49b1..bdfdb1cff653 100644
> > --- a/mm/kasan/kasan.h
> > +++ b/mm/kasan/kasan.h
> > @@ -224,7 +224,7 @@ void *find_first_bad_addr(void *addr, size_t size);
> > const char *get_bug_type(struct kasan_access_info *info);
> > void metadata_fetch_row(char *buffer, void *row);
> >
> > -#if defined(CONFIG_KASAN_GENERIC) && CONFIG_KASAN_STACK
> > +#if defined(CONFIG_KASAN_GENERIC) && defined(CONFIG_KASAN_STACK)
> > void print_address_stack_frame(const void *addr);
> > #else
> > static inline void print_address_stack_frame(const void *addr) { }
> > diff --git a/mm/kasan/report_generic.c b/mm/kasan/report_generic.c
> > index 8a9c889872da..4e16518d9877 100644
> > --- a/mm/kasan/report_generic.c
> > +++ b/mm/kasan/report_generic.c
> > @@ -128,7 +128,7 @@ void metadata_fetch_row(char *buffer, void *row)
> > memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
> > }
> >
> > -#if CONFIG_KASAN_STACK
> > +#ifdef CONFIG_KASAN_STACK
> > static bool __must_check tokenize_frame_descr(const char **frame_descr,
> > char *token, size_t max_tok_len,
> > unsigned long *value)
> > diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> > index 1e000cc2e7b4..abf231d209b1 100644
> > --- a/scripts/Makefile.kasan
> > +++ b/scripts/Makefile.kasan
> > @@ -2,6 +2,12 @@
> > CFLAGS_KASAN_NOSANITIZE := -fno-builtin
> > KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
> >
> > +ifdef CONFIG_KASAN_STACK
> > + stack_enable := 1
> > +else
> > + stack_enable := 0
> > +endif
> > +
> > ifdef CONFIG_KASAN_GENERIC
> >
> > ifdef CONFIG_KASAN_INLINE
> > @@ -27,7 +33,7 @@ else
> > CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
> > $(call cc-param,asan-globals=1) \
> > $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
> > - $(call cc-param,asan-stack=$(CONFIG_KASAN_STACK)) \
> > + $(call cc-param,asan-stack=$(stack_enable)) \
> > $(call cc-param,asan-instrument-allocas=1)
> > endif
> >
> > @@ -42,7 +48,7 @@ else
> > endif
> >
> > CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
> > - -mllvm -hwasan-instrument-stack=$(CONFIG_KASAN_STACK) \
> > + -mllvm -hwasan-instrument-stack=$(stack_enable) \
> > -mllvm -hwasan-use-short-granules=0 \
> > $(instrumentation_flags)
> >
> > --
> > 2.18.0
> >
> > --
> > You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
> > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20210108040940.1138-1-walter-zh.wu%40mediatek.com.

2021-01-11 19:08:29

by Andrey Konovalov

[permalink] [raw]

Subject: Re: [PATCH v3] kasan: remove redundant config option

On Mon, Jan 11, 2021 at 7:59 PM Nathan Chancellor
<[email protected]> wrote:
>
> > > -config KASAN_STACK_ENABLE
> > > +config KASAN_STACK
> > > bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
> >
> > Does this syntax mean that KASAN_STACK is only present for
> > CC_IS_CLANG? Or that it can only be disabled for CC_IS_CLANG?
>
> It means that the option can only be disabled for clang.

OK, got it.

> > Anyway, I think it's better to 1. allow to control KASAN_STACK
> > regardless of the compiler (as it was possible before), and 2. avoid
>
> It has never been possible to control KASAN_STACK for GCC because of the
> bool ... if ... syntax. This patch does not change that logic. Making it
> possible to control KASAN_STACK with GCC seems fine but that is going to
> be a new change that would probably be suited for a new patch on top of
> this one.

The if syntax was never applied to KASAN_STACK, only to
KASAN_STACK_ENABLE, so it should have been possible (although I've
never specifically tried it).

2021-01-11 19:15:53

by Nathan Chancellor

[permalink] [raw]

Subject: Re: [PATCH v3] kasan: remove redundant config option

On Mon, Jan 11, 2021 at 08:03:29PM +0100, Andrey Konovalov wrote:
> On Mon, Jan 11, 2021 at 7:59 PM Nathan Chancellor
> <[email protected]> wrote:
> >
> > > > -config KASAN_STACK_ENABLE
> > > > +config KASAN_STACK
> > > > bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
> > >
> > > Does this syntax mean that KASAN_STACK is only present for
> > > CC_IS_CLANG? Or that it can only be disabled for CC_IS_CLANG?
> >
> > It means that the option can only be disabled for clang.
>
> OK, got it.
>
> > > Anyway, I think it's better to 1. allow to control KASAN_STACK
> > > regardless of the compiler (as it was possible before), and 2. avoid
> >
> > It has never been possible to control KASAN_STACK for GCC because of the
> > bool ... if ... syntax. This patch does not change that logic. Making it
> > possible to control KASAN_STACK with GCC seems fine but that is going to
> > be a new change that would probably be suited for a new patch on top of
> > this one.
>
> The if syntax was never applied to KASAN_STACK, only to
> KASAN_STACK_ENABLE, so it should have been possible (although I've
> never specifically tried it).

CONFIG_KASAN_STACK was not a user selectable symbol so it was always 1
for GCC.

Cheers,
Nathan

2021-01-11 19:32:48

by Andrey Konovalov

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Subject: Re: [PATCH v3] kasan: remove redundant config option

On Mon, Jan 11, 2021 at 8:11 PM Nathan Chancellor
<[email protected]> wrote:
>
> On Mon, Jan 11, 2021 at 08:03:29PM +0100, Andrey Konovalov wrote:
> > On Mon, Jan 11, 2021 at 7:59 PM Nathan Chancellor
> > <[email protected]> wrote:
> > >
> > > > > -config KASAN_STACK_ENABLE
> > > > > +config KASAN_STACK
> > > > > bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
> > > >
> > > > Does this syntax mean that KASAN_STACK is only present for
> > > > CC_IS_CLANG? Or that it can only be disabled for CC_IS_CLANG?
> > >
> > > It means that the option can only be disabled for clang.
> >
> > OK, got it.
> >
> > > > Anyway, I think it's better to 1. allow to control KASAN_STACK
> > > > regardless of the compiler (as it was possible before), and 2. avoid
> > >
> > > It has never been possible to control KASAN_STACK for GCC because of the
> > > bool ... if ... syntax. This patch does not change that logic. Making it
> > > possible to control KASAN_STACK with GCC seems fine but that is going to
> > > be a new change that would probably be suited for a new patch on top of
> > > this one.
> >
> > The if syntax was never applied to KASAN_STACK, only to
> > KASAN_STACK_ENABLE, so it should have been possible (although I've
> > never specifically tried it).
>
> CONFIG_KASAN_STACK was not a user selectable symbol so it was always 1
> for GCC.

Ah, indeed.

Thanks for the clarification!

2021-01-11 19:34:14

by Andrey Konovalov

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