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Date:   Fri, 30 Oct 2020 00:40:38 -0700
From:   Nathan Chancellor <natechancellor@gmail.com>
To:     Joe Perches <joe@perches.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Ard Biesheuvel <ardb@kernel.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        Marco Elver <elver@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org,
        kasan-dev@googlegroups.com, linux-crypto@vger.kernel.org,
        linux-mm@kvack.org, clang-built-linux@googlegroups.com
Subject: Re: [PATCH] treewide: Remove stringification from __alias macro
 definition
Message-ID: <20201030074038.GA1747580@ubuntu-m3-large-x86>
References: <8451df41359b52f048780d19e07b6fa4445b6392.1604026698.git.joe@perches.com>
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In-Reply-To: <8451df41359b52f048780d19e07b6fa4445b6392.1604026698.git.joe@perches.com>
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On Thu, Oct 29, 2020 at 08:07:31PM -0700, Joe Perches wrote:
> Like the old __section macro, the __alias macro uses macro # stringification
> to create quotes around the symbol name used in the __attribute__.
> 
> This can cause differences between gcc and clang when the stringification
> itself contains a quote character.  So avoid these differences by always
> using quotes to define the aliased symbol.
> 
> Remove the stringification and add quotes and when necessary a stringification
> when existing uses have a ## concatenation.
> 
> Signed-off-by: Joe Perches <joe@perches.com>

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

> ---
> 
> Unlike the __section macro conversion in commit 33def8498fdd
> ("treewide: Convert macro and uses of __section(foo) to __section("foo")")
> this one was done by hand.
> 
> No other use of __alias exists in the kernel.
> 
> This patch does _not_ convert any uses of __attribute__((alias("<foo>")))
> so it should not cause any compilation issues.
> 
>  arch/x86/boot/compressed/string.c       |  6 +++---
>  arch/x86/include/asm/syscall_wrapper.h  |  2 +-
>  drivers/firmware/efi/runtime-wrappers.c |  2 +-
>  include/linux/compiler_attributes.h     |  2 +-
>  kernel/kcsan/core.c                     | 10 +++++-----
>  lib/crc32.c                             |  4 ++--
>  lib/crypto/aes.c                        |  4 ++--
>  mm/kasan/generic.c                      |  8 ++++----
>  8 files changed, 19 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/string.c b/arch/x86/boot/compressed/string.c
> index 81fc1eaa3229..d38b122f51ef 100644
> --- a/arch/x86/boot/compressed/string.c
> +++ b/arch/x86/boot/compressed/string.c
> @@ -75,7 +75,7 @@ void *memcpy(void *dest, const void *src, size_t n)
>  }
>  
>  #ifdef CONFIG_KASAN
> -extern void *__memset(void *s, int c, size_t n) __alias(memset);
> -extern void *__memmove(void *dest, const void *src, size_t n) __alias(memmove);
> -extern void *__memcpy(void *dest, const void *src, size_t n) __alias(memcpy);
> +extern void *__memset(void *s, int c, size_t n) __alias("memset");
> +extern void *__memmove(void *dest, const void *src, size_t n) __alias("memmove");
> +extern void *__memcpy(void *dest, const void *src, size_t n) __alias("memcpy");
>  #endif
> diff --git a/arch/x86/include/asm/syscall_wrapper.h b/arch/x86/include/asm/syscall_wrapper.h
> index a84333adeef2..f19d1bbbff3d 100644
> --- a/arch/x86/include/asm/syscall_wrapper.h
> +++ b/arch/x86/include/asm/syscall_wrapper.h
> @@ -69,7 +69,7 @@ extern long __ia32_sys_ni_syscall(const struct pt_regs *regs);
>  	long __##abi##_##name(const struct pt_regs *regs);		\
>  	ALLOW_ERROR_INJECTION(__##abi##_##name, ERRNO);			\
>  	long __##abi##_##name(const struct pt_regs *regs)		\
> -		__alias(__do_##name);
> +		__alias("__do_" #name);
>  
>  #define __SYS_STUBx(abi, name, ...)					\
>  	long __##abi##_##name(const struct pt_regs *regs);		\
> diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
> index 1410beaef5c3..14e380ac65d4 100644
> --- a/drivers/firmware/efi/runtime-wrappers.c
> +++ b/drivers/firmware/efi/runtime-wrappers.c
> @@ -162,7 +162,7 @@ static DEFINE_SEMAPHORE(efi_runtime_lock);
>   * Expose the EFI runtime lock to the UV platform
>   */
>  #ifdef CONFIG_X86_UV
> -extern struct semaphore __efi_uv_runtime_lock __alias(efi_runtime_lock);
> +extern struct semaphore __efi_uv_runtime_lock __alias("efi_runtime_lock");
>  #endif
>  
>  /*
> diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
> index ea7b756b1c8f..4819512c9abd 100644
> --- a/include/linux/compiler_attributes.h
> +++ b/include/linux/compiler_attributes.h
> @@ -42,7 +42,7 @@
>  /*
>   *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
>   */
> -#define __alias(symbol)                 __attribute__((__alias__(#symbol)))
> +#define __alias(symbol)                 __attribute__((__alias__(symbol)))
>  
>  /*
>   *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-aligned-function-attribute
> diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
> index 3994a217bde7..465f6cfc317c 100644
> --- a/kernel/kcsan/core.c
> +++ b/kernel/kcsan/core.c
> @@ -814,7 +814,7 @@ EXPORT_SYMBOL(__kcsan_check_access);
>  	}                                                                      \
>  	EXPORT_SYMBOL(__tsan_read##size);                                      \
>  	void __tsan_unaligned_read##size(void *ptr)                            \
> -		__alias(__tsan_read##size);                                    \
> +		__alias("__tsan_read" #size);                                  \
>  	EXPORT_SYMBOL(__tsan_unaligned_read##size);                            \
>  	void __tsan_write##size(void *ptr);                                    \
>  	void __tsan_write##size(void *ptr)                                     \
> @@ -823,7 +823,7 @@ EXPORT_SYMBOL(__kcsan_check_access);
>  	}                                                                      \
>  	EXPORT_SYMBOL(__tsan_write##size);                                     \
>  	void __tsan_unaligned_write##size(void *ptr)                           \
> -		__alias(__tsan_write##size);                                   \
> +		__alias("__tsan_write" #size);                                 \
>  	EXPORT_SYMBOL(__tsan_unaligned_write##size);                           \
>  	void __tsan_read_write##size(void *ptr);                               \
>  	void __tsan_read_write##size(void *ptr)                                \
> @@ -833,7 +833,7 @@ EXPORT_SYMBOL(__kcsan_check_access);
>  	}                                                                      \
>  	EXPORT_SYMBOL(__tsan_read_write##size);                                \
>  	void __tsan_unaligned_read_write##size(void *ptr)                      \
> -		__alias(__tsan_read_write##size);                              \
> +		__alias("__tsan_read_write" #size);                            \
>  	EXPORT_SYMBOL(__tsan_unaligned_read_write##size)
>  
>  DEFINE_TSAN_READ_WRITE(1);
> @@ -877,7 +877,7 @@ EXPORT_SYMBOL(__tsan_write_range);
>  	}                                                                      \
>  	EXPORT_SYMBOL(__tsan_volatile_read##size);                             \
>  	void __tsan_unaligned_volatile_read##size(void *ptr)                   \
> -		__alias(__tsan_volatile_read##size);                           \
> +		__alias("__tsan_volatile_read" #size);                         \
>  	EXPORT_SYMBOL(__tsan_unaligned_volatile_read##size);                   \
>  	void __tsan_volatile_write##size(void *ptr);                           \
>  	void __tsan_volatile_write##size(void *ptr)                            \
> @@ -892,7 +892,7 @@ EXPORT_SYMBOL(__tsan_write_range);
>  	}                                                                      \
>  	EXPORT_SYMBOL(__tsan_volatile_write##size);                            \
>  	void __tsan_unaligned_volatile_write##size(void *ptr)                  \
> -		__alias(__tsan_volatile_write##size);                          \
> +		__alias("__tsan_volatile_write" #size);                        \
>  	EXPORT_SYMBOL(__tsan_unaligned_volatile_write##size)
>  
>  DEFINE_TSAN_VOLATILE_READ_WRITE(1);
> diff --git a/lib/crc32.c b/lib/crc32.c
> index 2a68dfd3b96c..373a17aaa432 100644
> --- a/lib/crc32.c
> +++ b/lib/crc32.c
> @@ -206,8 +206,8 @@ u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len)
>  EXPORT_SYMBOL(crc32_le);
>  EXPORT_SYMBOL(__crc32c_le);
>  
> -u32 __pure crc32_le_base(u32, unsigned char const *, size_t) __alias(crc32_le);
> -u32 __pure __crc32c_le_base(u32, unsigned char const *, size_t) __alias(__crc32c_le);
> +u32 __pure crc32_le_base(u32, unsigned char const *, size_t) __alias("crc32_le");
> +u32 __pure __crc32c_le_base(u32, unsigned char const *, size_t) __alias("__crc32c_le");
>  
>  /*
>   * This multiplies the polynomials x and y modulo the given modulus.
> diff --git a/lib/crypto/aes.c b/lib/crypto/aes.c
> index 827fe89922ff..5b80514595c2 100644
> --- a/lib/crypto/aes.c
> +++ b/lib/crypto/aes.c
> @@ -82,8 +82,8 @@ static volatile const u8 __cacheline_aligned aes_inv_sbox[] = {
>  	0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d,
>  };
>  
> -extern const u8 crypto_aes_sbox[256] __alias(aes_sbox);
> -extern const u8 crypto_aes_inv_sbox[256] __alias(aes_inv_sbox);
> +extern const u8 crypto_aes_sbox[256] __alias("aes_sbox");
> +extern const u8 crypto_aes_inv_sbox[256] __alias("aes_inv_sbox");
>  
>  EXPORT_SYMBOL(crypto_aes_sbox);
>  EXPORT_SYMBOL(crypto_aes_inv_sbox);
> diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
> index 248264b9cb76..4496f897e4f5 100644
> --- a/mm/kasan/generic.c
> +++ b/mm/kasan/generic.c
> @@ -234,7 +234,7 @@ EXPORT_SYMBOL(__asan_unregister_globals);
>  		check_memory_region_inline(addr, size, false, _RET_IP_);\
>  	}								\
>  	EXPORT_SYMBOL(__asan_load##size);				\
> -	__alias(__asan_load##size)					\
> +	__alias("__asan_load" #size)					\
>  	void __asan_load##size##_noabort(unsigned long);		\
>  	EXPORT_SYMBOL(__asan_load##size##_noabort);			\
>  	void __asan_store##size(unsigned long addr)			\
> @@ -242,7 +242,7 @@ EXPORT_SYMBOL(__asan_unregister_globals);
>  		check_memory_region_inline(addr, size, true, _RET_IP_);	\
>  	}								\
>  	EXPORT_SYMBOL(__asan_store##size);				\
> -	__alias(__asan_store##size)					\
> +	__alias("__asan_store" #size)					\
>  	void __asan_store##size##_noabort(unsigned long);		\
>  	EXPORT_SYMBOL(__asan_store##size##_noabort)
>  
> @@ -258,7 +258,7 @@ void __asan_loadN(unsigned long addr, size_t size)
>  }
>  EXPORT_SYMBOL(__asan_loadN);
>  
> -__alias(__asan_loadN)
> +__alias("__asan_loadN")
>  void __asan_loadN_noabort(unsigned long, size_t);
>  EXPORT_SYMBOL(__asan_loadN_noabort);
>  
> @@ -268,7 +268,7 @@ void __asan_storeN(unsigned long addr, size_t size)
>  }
>  EXPORT_SYMBOL(__asan_storeN);
>  
> -__alias(__asan_storeN)
> +__alias("__asan_storeN")
>  void __asan_storeN_noabort(unsigned long, size_t);
>  EXPORT_SYMBOL(__asan_storeN_noabort);
>  
> -- 
> 2.26.0
>