[PATCH 1/3] compiler-gcc.h: Introduce __optimize function attribute

[PATCH 1/3] compiler-gcc.h: Introduce __optimize function attribute

[Geert Uytterhoeven]

Create a new function attribute __optimize, which allows to specify an
optimization level on a per-function basis.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
I assume this is supported as of gcc-4.4:
  - gcc version 4.3.3 (GCC): warning: ‘__optimize__’ attribute directive
    ignored
  - gcc version 4.4.7 (Ubuntu/Linaro 4.4.7-1ubuntu2): OK
---
 include/linux/compiler-gcc.h | 4 ++++
 include/linux/compiler.h     | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 631354acfa720475..0a278a527944ad2f 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -196,6 +196,10 @@
 #endif /* __CHECKER__ */
 #endif /* GCC_VERSION >= 40300 */
 
+#if GCC_VERSION >= 40400
+#define __optimize(level)	__attribute__((__optimize__(level)))
+#endif /* GCC_VERSION >= 40400 */
+
 #if GCC_VERSION >= 40500
 
 #ifndef __CHECKER__
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 52e611ab9a6cf6fd..5ff818e9a836e898 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -271,6 +271,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
 
 #endif /* __ASSEMBLY__ */
 
+#ifndef __optimize
+# define __optimize(level)
+#endif
+
 /* Compile time object size, -1 for unknown */
 #ifndef __compiletime_object_size
 # define __compiletime_object_size(obj) -1
-- 
2.7.4

[PATCH 2/3] compiler-gcc.h: __nostackprotector needs gcc-4.4 and up

[Geert Uytterhoeven]

Gcc versions before 4.4 do not recognize the __optimize__ compiler
attribute:

    warning: ‘__optimize__’ attribute directive ignored

Fixes: 7375ae3a0b79ea07 ("compiler-gcc.h: Introduce __nostackprotector function attribute")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
Can anyone please verify this?
Apparently __nostackprotector is used on x86 only, which is usually
served by modern compilers.
---
 include/linux/compiler-gcc.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 0a278a527944ad2f..73bc63e0a1c4b664 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -167,8 +167,6 @@
 
 #if GCC_VERSION >= 40100
 # define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
-
-#define __nostackprotector	__attribute__((__optimize__("no-stack-protector")))
 #endif
 
 #if GCC_VERSION >= 40300
@@ -198,6 +196,7 @@
 
 #if GCC_VERSION >= 40400
 #define __optimize(level)	__attribute__((__optimize__(level)))
+#define __nostackprotector	__optimize("no-stack-protector")
 #endif /* GCC_VERSION >= 40400 */
 
 #if GCC_VERSION >= 40500
-- 
2.7.4

Re: [PATCH 2/3] compiler-gcc.h: __nostackprotector needs gcc-4.4 and up

[Arnd Bergmann]

On Thu, Feb 1, 2018 at 11:21 AM, Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
> Gcc versions before 4.4 do not recognize the __optimize__ compiler
> attribute:
>
>     warning: ‘__optimize__’ attribute directive ignored
>
> Fixes: 7375ae3a0b79ea07 ("compiler-gcc.h: Introduce __nostackprotector function attribute")
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> ---
> Can anyone please verify this?
> Apparently __nostackprotector is used on x86 only, which is usually
> served by modern compilers.

I've checked that __optimize("no-stack-protector") is accepted by exactly those
compilers that your 40400 version check tests for, across all architectures, so
that's fine.

However,  looking at commit 91cfc88c66bf ("x86: Use __nostackprotect for
sme_encrypt_kernel"), I suspect that gcc-4.1 through 4.3 will now cause
a runtime failure in sme_encrypt_kernel() without a compile-time warning.

I would leave __nostackprotector unchanged here, so we at least get
a warning for functions that need to disable the stack protector to work
correctly.

We might want to add an #ifdef CONFIG_CC_STACKPROTECTOR around
the __nostackprotector definition, so that we only warn if stackprotector
is globally enabled.

       Arnd

Re: [PATCH 2/3] compiler-gcc.h: __nostackprotector needs gcc-4.4 and up

[Geert Uytterhoeven]

Hi Arnd,

On Thu, Feb 1, 2018 at 12:46 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> On Thu, Feb 1, 2018 at 11:21 AM, Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
>> Gcc versions before 4.4 do not recognize the __optimize__ compiler
>> attribute:
>>
>>     warning: ‘__optimize__’ attribute directive ignored
>>
>> Fixes: 7375ae3a0b79ea07 ("compiler-gcc.h: Introduce __nostackprotector function attribute")
>> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
>> ---
>> Can anyone please verify this?
>> Apparently __nostackprotector is used on x86 only, which is usually
>> served by modern compilers.
>
> I've checked that __optimize("no-stack-protector") is accepted by exactly those
> compilers that your 40400 version check tests for, across all architectures, so
> that's fine.

Thanks!

> However,  looking at commit 91cfc88c66bf ("x86: Use __nostackprotect for
> sme_encrypt_kernel"), I suspect that gcc-4.1 through 4.3 will now cause
> a runtime failure in sme_encrypt_kernel() without a compile-time warning.

So having this functionality is a hard requirement. Oops...

> I would leave __nostackprotector unchanged here, so we at least get
> a warning for functions that need to disable the stack protector to work
> correctly.

Agreed.

> We might want to add an #ifdef CONFIG_CC_STACKPROTECTOR around
> the __nostackprotector definition, so that we only warn if stackprotector
> is globally enabled.

And we might want to remove the dummy in include/linux/compiler_types.h:

#ifndef __nostackprotector
# define __nostackprotector
#endif

BTW, how does this work with non-gcc compilers?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH 2/3] compiler-gcc.h: __nostackprotector needs gcc-4.4 and up

[Arnd Bergmann]

On Thu, Feb 1, 2018 at 12:55 PM, Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
> Hi Arnd,
>
> On Thu, Feb 1, 2018 at 12:46 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>> On Thu, Feb 1, 2018 at 11:21 AM, Geert Uytterhoeven
>> <geert@linux-m68k.org> wrote:
>>> Gcc versions before 4.4 do not recognize the __optimize__ compiler
>>> attribute:

>
> And we might want to remove the dummy in include/linux/compiler_types.h:
>
> #ifndef __nostackprotector
> # define __nostackprotector
> #endif
>
> BTW, how does this work with non-gcc compilers?

clang should in theory accept the same flags, and it pretends to be an older
version of gcc.

I don't think anyone cares about ICC or any other compiler.

    Arnd

[PATCH 3/3] crypto: sha3-generic - Use __optimize to support old compilers

[Geert Uytterhoeven]

With gcc-4.1.2:

    crypto/sha3_generic.c:39: warning: ‘__optimize__’ attribute directive ignored

Use the newly introduced __optimize macro to fix this.

Fixes: 83dee2ce1ae791c3 ("crypto: sha3-generic - rewrite KECCAK transform to help the compiler optimize")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
 crypto/sha3_generic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crypto/sha3_generic.c b/crypto/sha3_generic.c
index a965b9d8055983af..c409cd87fea5decd 100644
--- a/crypto/sha3_generic.c
+++ b/crypto/sha3_generic.c
@@ -35,7 +35,7 @@ static const u64 keccakf_rndc[24] = {
 
 /* update the state with given number of rounds */
 
-static void __attribute__((__optimize__("O3"))) keccakf(u64 st[25])
+static void __optimize("O3") keccakf(u64 st[25])
 {
 	u64 t[5], tt, bc[5];
 	int round;
-- 
2.7.4

Re: [PATCH 3/3] crypto: sha3-generic - Use __optimize to support old compilers

[Ard Biesheuvel]

On 1 February 2018 at 10:22, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> With gcc-4.1.2:
>
>     crypto/sha3_generic.c:39: warning: ‘__optimize__’ attribute directive ignored
>
> Use the newly introduced __optimize macro to fix this.
>
> Fixes: 83dee2ce1ae791c3 ("crypto: sha3-generic - rewrite KECCAK transform to help the compiler optimize")
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---
>  crypto/sha3_generic.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/crypto/sha3_generic.c b/crypto/sha3_generic.c
> index a965b9d8055983af..c409cd87fea5decd 100644
> --- a/crypto/sha3_generic.c
> +++ b/crypto/sha3_generic.c
> @@ -35,7 +35,7 @@ static const u64 keccakf_rndc[24] = {
>
>  /* update the state with given number of rounds */
>
> -static void __attribute__((__optimize__("O3"))) keccakf(u64 st[25])
> +static void __optimize("O3") keccakf(u64 st[25])
>  {
>         u64 t[5], tt, bc[5];
>         int round;
> --
> 2.7.4
>

Re: [PATCH 1/3] compiler-gcc.h: Introduce __optimize function attribute

[Ard Biesheuvel]

On 1 February 2018 at 10:21, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> Create a new function attribute __optimize, which allows to specify an
> optimization level on a per-function basis.
>
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---
> I assume this is supported as of gcc-4.4:
>   - gcc version 4.3.3 (GCC): warning: ‘__optimize__’ attribute directive
>     ignored
>   - gcc version 4.4.7 (Ubuntu/Linaro 4.4.7-1ubuntu2): OK
> ---
>  include/linux/compiler-gcc.h | 4 ++++
>  include/linux/compiler.h     | 4 ++++
>  2 files changed, 8 insertions(+)
>
> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> index 631354acfa720475..0a278a527944ad2f 100644
> --- a/include/linux/compiler-gcc.h
> +++ b/include/linux/compiler-gcc.h
> @@ -196,6 +196,10 @@
>  #endif /* __CHECKER__ */
>  #endif /* GCC_VERSION >= 40300 */
>
> +#if GCC_VERSION >= 40400
> +#define __optimize(level)      __attribute__((__optimize__(level)))
> +#endif /* GCC_VERSION >= 40400 */
> +
>  #if GCC_VERSION >= 40500
>
>  #ifndef __CHECKER__
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 52e611ab9a6cf6fd..5ff818e9a836e898 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -271,6 +271,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
>
>  #endif /* __ASSEMBLY__ */
>
> +#ifndef __optimize
> +# define __optimize(level)
> +#endif
> +
>  /* Compile time object size, -1 for unknown */
>  #ifndef __compiletime_object_size
>  # define __compiletime_object_size(obj) -1
> --
> 2.7.4
>