* [PATCH] init: verify that function is initcall_t at compile-time
@ 2021-05-21 7:26 Marco Elver
2021-05-21 16:36 ` Sami Tolvanen
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Marco Elver @ 2021-05-21 7:26 UTC (permalink / raw)
To: elver
Cc: linux-kernel, keescook, samitolvanen, ojeda, johan, akpm,
masahiroy, joe, Arnd Bergmann, Paul E. McKenney,
Nathan Chancellor
In the spirit of making it hard to misuse an interface, add a
compile-time assertion in the CONFIG_HAVE_ARCH_PREL32_RELOCATIONS case
to verify the initcall function matches initcall_t, because the inline
asm bypasses any type-checking the compiler would otherwise do. This
will help developers catch incorrect API use in all configurations.
A recent example of this is:
https://lkml.kernel.org/r/20210514140015.2944744-1-arnd@kernel.org
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
---
include/linux/init.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/linux/init.h b/include/linux/init.h
index 045ad1650ed1..d82b4b2e1d25 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -242,7 +242,8 @@ extern bool initcall_debug;
asm(".section \"" __sec "\", \"a\" \n" \
__stringify(__name) ": \n" \
".long " __stringify(__stub) " - . \n" \
- ".previous \n");
+ ".previous \n"); \
+ static_assert(__same_type(initcall_t, &fn));
#else
#define ____define_initcall(fn, __unused, __name, __sec) \
static initcall_t __name __used \
--
2.31.1.818.g46aad6cb9e-goog
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] init: verify that function is initcall_t at compile-time
2021-05-21 7:26 [PATCH] init: verify that function is initcall_t at compile-time Marco Elver
@ 2021-05-21 16:36 ` Sami Tolvanen
2021-05-21 17:32 ` Paul E. McKenney
2021-05-21 17:59 ` Kees Cook
2 siblings, 0 replies; 4+ messages in thread
From: Sami Tolvanen @ 2021-05-21 16:36 UTC (permalink / raw)
To: Marco Elver
Cc: LKML, Kees Cook, ojeda, johan, Andrew Morton, Masahiro Yamada,
Joe Perches, Arnd Bergmann, Paul E. McKenney, Nathan Chancellor
Hi Marco,
On Fri, May 21, 2021 at 12:26 AM Marco Elver <elver@google.com> wrote:
>
> In the spirit of making it hard to misuse an interface, add a
> compile-time assertion in the CONFIG_HAVE_ARCH_PREL32_RELOCATIONS case
> to verify the initcall function matches initcall_t, because the inline
> asm bypasses any type-checking the compiler would otherwise do. This
> will help developers catch incorrect API use in all configurations.
>
> A recent example of this is:
> https://lkml.kernel.org/r/20210514140015.2944744-1-arnd@kernel.org
>
> Signed-off-by: Marco Elver <elver@google.com>
> Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> Tested-by: Nathan Chancellor <nathan@kernel.org>
> ---
> include/linux/init.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/init.h b/include/linux/init.h
> index 045ad1650ed1..d82b4b2e1d25 100644
> --- a/include/linux/init.h
> +++ b/include/linux/init.h
> @@ -242,7 +242,8 @@ extern bool initcall_debug;
> asm(".section \"" __sec "\", \"a\" \n" \
> __stringify(__name) ": \n" \
> ".long " __stringify(__stub) " - . \n" \
> - ".previous \n");
> + ".previous \n"); \
> + static_assert(__same_type(initcall_t, &fn));
> #else
> #define ____define_initcall(fn, __unused, __name, __sec) \
> static initcall_t __name __used \
This looks like a nice improvement, thank you for sending the patch!
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Sami
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] init: verify that function is initcall_t at compile-time
2021-05-21 7:26 [PATCH] init: verify that function is initcall_t at compile-time Marco Elver
2021-05-21 16:36 ` Sami Tolvanen
@ 2021-05-21 17:32 ` Paul E. McKenney
2021-05-21 17:59 ` Kees Cook
2 siblings, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2021-05-21 17:32 UTC (permalink / raw)
To: Marco Elver
Cc: linux-kernel, keescook, samitolvanen, ojeda, johan, akpm,
masahiroy, joe, Arnd Bergmann, Nathan Chancellor
On Fri, May 21, 2021 at 09:26:10AM +0200, Marco Elver wrote:
> In the spirit of making it hard to misuse an interface, add a
> compile-time assertion in the CONFIG_HAVE_ARCH_PREL32_RELOCATIONS case
> to verify the initcall function matches initcall_t, because the inline
> asm bypasses any type-checking the compiler would otherwise do. This
> will help developers catch incorrect API use in all configurations.
>
> A recent example of this is:
> https://lkml.kernel.org/r/20210514140015.2944744-1-arnd@kernel.org
>
> Signed-off-by: Marco Elver <elver@google.com>
> Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
> ---
> include/linux/init.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/init.h b/include/linux/init.h
> index 045ad1650ed1..d82b4b2e1d25 100644
> --- a/include/linux/init.h
> +++ b/include/linux/init.h
> @@ -242,7 +242,8 @@ extern bool initcall_debug;
> asm(".section \"" __sec "\", \"a\" \n" \
> __stringify(__name) ": \n" \
> ".long " __stringify(__stub) " - . \n" \
> - ".previous \n");
> + ".previous \n"); \
> + static_assert(__same_type(initcall_t, &fn));
> #else
> #define ____define_initcall(fn, __unused, __name, __sec) \
> static initcall_t __name __used \
> --
> 2.31.1.818.g46aad6cb9e-goog
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] init: verify that function is initcall_t at compile-time
2021-05-21 7:26 [PATCH] init: verify that function is initcall_t at compile-time Marco Elver
2021-05-21 16:36 ` Sami Tolvanen
2021-05-21 17:32 ` Paul E. McKenney
@ 2021-05-21 17:59 ` Kees Cook
2 siblings, 0 replies; 4+ messages in thread
From: Kees Cook @ 2021-05-21 17:59 UTC (permalink / raw)
To: Marco Elver
Cc: Kees Cook, Paul E. McKenney, linux-kernel, ojeda, akpm, joe,
johan, masahiroy, Nathan Chancellor, Arnd Bergmann, samitolvanen
On Fri, 21 May 2021 09:26:10 +0200, Marco Elver wrote:
> In the spirit of making it hard to misuse an interface, add a
> compile-time assertion in the CONFIG_HAVE_ARCH_PREL32_RELOCATIONS case
> to verify the initcall function matches initcall_t, because the inline
> asm bypasses any type-checking the compiler would otherwise do. This
> will help developers catch incorrect API use in all configurations.
>
> A recent example of this is:
> https://lkml.kernel.org/r/20210514140015.2944744-1-arnd@kernel.org
Since this touches on CFI, I've taken this patch.
Applied to for-next/clang/features, thanks!
[1/1] init: verify that function is initcall_t at compile-time
https://git.kernel.org/kees/c/72a12a91a634
--
Kees Cook
^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-05-21 7:26 [PATCH] init: verify that function is initcall_t at compile-time Marco Elver
2021-05-21 16:36 ` Sami Tolvanen
2021-05-21 17:32 ` Paul E. McKenney
2021-05-21 17:59 ` Kees Cook
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