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Date: Sun, 19 Aug 2018 14:23:49 -0700
From: Kees Cook <keescook@...omium.org>
To: Joe Perches <joe@...ches.com>
Cc: Guenter Roeck <linux@...ck-us.net>,
LKML <linux-kernel@...r.kernel.org>,
Rik van Riel <riel@...riel.com>,
Mike Galbraith <efault@....de>,
Dave Hansen <dave.hansen@...el.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Build failures with gcc 4.5 and older
On Tue, Aug 14, 2018 at 10:48 AM, Joe Perches <joe@...ches.com> wrote:
> On Tue, 2018-08-14 at 10:09 -0700, Guenter Roeck wrote:
>> Hi,
>>
>> Since commit c1a2f7f0c0645 ("mm: Allocate the mm_cpumask
>> (mm->cpu_bitmap[]) dynamically based on nr_cpu_ids"), building
>> the Linux kernel with gcc version 4.5 and older fails as follows.
>>
>> In file included from ./include/linux/mm.h:17:0,
>> from ./include/linux/pid_namespace.h:7,
>> from ./include/linux/ptrace.h:10,
>> from arch/openrisc/kernel/asm-offsets.c:32:
>> ./include/linux/mm_types.h:497:16: error: flexible array member in otherwise empty struct
>>
>> This is just an example with gcc 4.5.1 for or32. I have seen the problem
>> with gcc 4.4 (for unicore32) as well.
>>
>> Does that mean that gcc 4.5 and older are now officially no longer
>> supported for compiling the kernel ?
>>
>> If so, would it make sense to update include/linux/compiler-gcc.h
>> accordingly ?
>
> And Documentation/process/changes.rst which shows a
> minimum version required of gcc as 3.2, etc...
>
> With cleaning up now unnecessary version tests in
> compiler-gcc.h, something like:
I rejoice at raising the minimum gcc to version 4.6! :)
> ---
> Documentation/process/changes.rst | 2 +-
> include/linux/compiler-gcc.h | 86 ++++++++-------------------------------
> 2 files changed, 19 insertions(+), 69 deletions(-)
These look good, thanks:
Reviewed-by: Kees Cook <keescook@...omium.org>
-Kees
>
> diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
> index 7a92a06f90de..61f918b10a0c 100644
> --- a/Documentation/process/changes.rst
> +++ b/Documentation/process/changes.rst
> @@ -29,7 +29,7 @@ you probably needn't concern yourself with isdn4k-utils.
> ====================== =============== ========================================
> Program Minimal version Command to check the version
> ====================== =============== ========================================
> -GNU C 3.2 gcc --version
> +GNU C 4.6 gcc --version
> GNU make 3.81 make --version
> binutils 2.20 ld -v
> flex 2.5.35 flex --version
> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> index 573f5a7d42d4..020e4b9eee5c 100644
> --- a/include/linux/compiler-gcc.h
> +++ b/include/linux/compiler-gcc.h
> @@ -10,6 +10,10 @@
> + __GNUC_MINOR__ * 100 \
> + __GNUC_PATCHLEVEL__)
>
> +#if GCC_VERSION < 40600
> +# error Sorry, your compiler is too old - please upgrade it.
> +#endif
> +
> /* Optimization barrier */
>
> /* The "volatile" is due to gcc bugs */
> @@ -58,6 +62,12 @@
> #define OPTIMIZER_HIDE_VAR(var) \
> __asm__ ("" : "=r" (var) : "0" (var))
>
> +/*
> + * A trick to suppress uninitialized variable warning without generating any
> + * code
> + */
> +#define uninitialized_var(x) x = x
> +
> #ifdef __CHECKER__
> #define __must_be_array(a) 0
> #else
> @@ -91,7 +101,7 @@
> * A lot of inline functions can cause havoc with function tracing.
> */
> #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
> - !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
> + !defined(CONFIG_OPTIMIZE_INLINING)
> #define inline \
> inline __attribute__((always_inline, unused)) notrace __gnu_inline
> #else
> @@ -148,47 +158,13 @@
> #define __always_unused __attribute__((unused))
> #define __mode(x) __attribute__((mode(x)))
>
> -/* gcc version specific checks */
> -
> -#if GCC_VERSION < 30200
> -# error Sorry, your compiler is too old - please upgrade it.
> -#endif
> -
> -#if GCC_VERSION < 30300
> -# define __used __attribute__((__unused__))
> -#else
> -# define __used __attribute__((__used__))
> -#endif
> -
> -#ifdef CONFIG_GCOV_KERNEL
> -# if GCC_VERSION < 30400
> -# error "GCOV profiling support for gcc versions below 3.4 not included"
> -# endif /* __GNUC_MINOR__ */
> -#endif /* CONFIG_GCOV_KERNEL */
> -
> -#if GCC_VERSION >= 30400
> #define __must_check __attribute__((warn_unused_result))
> #define __malloc __attribute__((__malloc__))
> -#endif
> -
> -#if GCC_VERSION >= 40000
> -
> -/* GCC 4.1.[01] miscompiles __weak */
> -#ifdef __KERNEL__
> -# if GCC_VERSION >= 40100 && GCC_VERSION <= 40101
> -# error Your version of gcc miscompiles the __weak directive
> -# endif
> -#endif
>
> #define __used __attribute__((__used__))
> #define __compiler_offsetof(a, b) \
> __builtin_offsetof(a, b)
>
> -#if GCC_VERSION >= 40100
> -# define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
> -#endif
> -
> -#if GCC_VERSION >= 40300
> /* Mark functions as cold. gcc will assume any path leading to a call
> * to them will be unlikely. This means a lot of manual unlikely()s
> * are unnecessary now for any paths leading to the usual suspects
> @@ -207,24 +183,19 @@
>
> #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
>
> -#ifndef __CHECKER__
> -# define __compiletime_warning(message) __attribute__((warning(message)))
> -# define __compiletime_error(message) __attribute__((error(message)))
> -#endif /* __CHECKER__ */
> -#endif /* GCC_VERSION >= 40300 */
> -
> -#if GCC_VERSION >= 40400
> #define __optimize(level) __attribute__((__optimize__(level)))
> #define __nostackprotector __optimize("no-stack-protector")
> -#endif /* GCC_VERSION >= 40400 */
>
> -#if GCC_VERSION >= 40500
> +#define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
>
> #ifndef __CHECKER__
> +#define __compiletime_warning(message) __attribute__((warning(message)))
> +#define __compiletime_error(message) __attribute__((error(message)))
> +
> #ifdef LATENT_ENTROPY_PLUGIN
> #define __latent_entropy __attribute__((latent_entropy))
> #endif
> -#endif
> +#endif /* __CHECKER__ */
>
> /*
> * calling noreturn functions, __builtin_unreachable() and __builtin_trap()
> @@ -262,10 +233,6 @@
> #define randomized_struct_fields_end } __randomize_layout;
> #endif
>
> -#endif /* GCC_VERSION >= 40500 */
> -
> -#if GCC_VERSION >= 40600
> -
> /*
> * When used with Link Time Optimization, gcc can optimize away C functions or
> * variables which are referenced only from assembly code. __visible tells the
> @@ -274,8 +241,7 @@
> */
> #define __visible __attribute__((externally_visible))
>
> -#endif /* GCC_VERSION >= 40600 */
> -
> +/* gcc version specific checks */
>
> #if GCC_VERSION >= 40900 && !defined(__CHECKER__)
> /*
> @@ -309,10 +275,8 @@
> * folding in __builtin_bswap*() (yet), so don't set these for it.
> */
> #if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
> -#if GCC_VERSION >= 40400
> #define __HAVE_BUILTIN_BSWAP32__
> #define __HAVE_BUILTIN_BSWAP64__
> -#endif
> #if GCC_VERSION >= 40800
> #define __HAVE_BUILTIN_BSWAP16__
> #endif
> @@ -341,10 +305,9 @@
> * https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html
> */
> #define __designated_init __attribute__((designated_init))
> +#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
> #endif
>
> -#endif /* gcc version >= 40000 specific checks */
> -
> #if !defined(__noclone)
> #define __noclone /* not needed */
> #endif
> @@ -353,16 +316,6 @@
> #define __no_sanitize_address
> #endif
>
> -/*
> - * A trick to suppress uninitialized variable warning without generating any
> - * code
> - */
> -#define uninitialized_var(x) x = x
> -
> -#if GCC_VERSION >= 50100
> -#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
> -#endif
> -
> /*
> * Turn individual warnings and errors on and off locally, depending
> * on version.
> @@ -375,12 +328,9 @@
> #define __diag_GCC_warn warning
> #define __diag_GCC_error error
>
> -/* Compilers before gcc-4.6 do not understand "#pragma GCC diagnostic push" */
> -#if GCC_VERSION >= 40600
> #define __diag_str1(s) #s
> #define __diag_str(s) __diag_str1(s)
> #define __diag(s) _Pragma(__diag_str(GCC diagnostic s))
> -#endif
>
> #if GCC_VERSION >= 80000
> #define __diag_GCC_8(s) __diag(s)
>
>
>
--
Kees Cook
Pixel Security
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