From: Masahiro Yamada <masahiroy@kernel.org> To: patches@armlinux.org.uk Cc: linux-kernel@vger.kernel.org, Russell King <linux@armlinux.org.uk>, Masahiro Yamada <masahiroy@kernel.org>, Ard Biesheuvel <ardb@kernel.org>, linux-arm-kernel@lists.infradead.org Subject: [PATCH] ARM: fix get_user() broken with veneer Date: Wed, 27 Sep 2023 01:09:03 +0900 [thread overview] Message-ID: <20230926160903.62924-1-masahiroy@kernel.org> (raw) The 32-bit ARM kernel stops working if the kernel grows to the point where veneers for __get_user_* are created. AAPCS32 [1] states, "Register r12 (IP) may be used by a linker as a scratch register between a routine and any subroutine it calls. It can also be used within a routine to hold intermediate values between subroutine calls." However, bl instructions buried within the inline asm are unpredictable for compilers; hence, "ip" must be added to the clobber list. This becomes critical when veneers for __get_user_* are created because veneers use the ip register since commit 02e541db0540 ("ARM: 8323/1: force linker to use PIC veneers"). [1]: https://github.com/ARM-software/abi-aa/blob/2023Q1/aapcs32/aapcs32.rst Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> --- KernelVersion: v6.6-rc1 arch/arm/include/asm/uaccess.h | 14 ++------------ 1 file changed, 2 insertions(+), 12 deletions(-) diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h index bb5c81823117..c28f5ec21e41 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -109,16 +109,6 @@ extern int __get_user_64t_1(void *); extern int __get_user_64t_2(void *); extern int __get_user_64t_4(void *); -#define __GUP_CLOBBER_1 "lr", "cc" -#ifdef CONFIG_CPU_USE_DOMAINS -#define __GUP_CLOBBER_2 "ip", "lr", "cc" -#else -#define __GUP_CLOBBER_2 "lr", "cc" -#endif -#define __GUP_CLOBBER_4 "lr", "cc" -#define __GUP_CLOBBER_32t_8 "lr", "cc" -#define __GUP_CLOBBER_8 "lr", "cc" - #define __get_user_x(__r2, __p, __e, __l, __s) \ __asm__ __volatile__ ( \ __asmeq("%0", "r0") __asmeq("%1", "r2") \ @@ -126,7 +116,7 @@ extern int __get_user_64t_4(void *); "bl __get_user_" #__s \ : "=&r" (__e), "=r" (__r2) \ : "0" (__p), "r" (__l) \ - : __GUP_CLOBBER_##__s) + : "ip", "lr", "cc") /* narrowing a double-word get into a single 32bit word register: */ #ifdef __ARMEB__ @@ -148,7 +138,7 @@ extern int __get_user_64t_4(void *); "bl __get_user_64t_" #__s \ : "=&r" (__e), "=r" (__r2) \ : "0" (__p), "r" (__l) \ - : __GUP_CLOBBER_##__s) + : "ip", "lr", "cc") #else #define __get_user_x_64t __get_user_x #endif -- 2.39.2
WARNING: multiple messages have this Message-ID (diff)
From: Masahiro Yamada <masahiroy@kernel.org> To: patches@armlinux.org.uk Cc: linux-kernel@vger.kernel.org, Russell King <linux@armlinux.org.uk>, Masahiro Yamada <masahiroy@kernel.org>, Ard Biesheuvel <ardb@kernel.org>, linux-arm-kernel@lists.infradead.org Subject: [PATCH] ARM: fix get_user() broken with veneer Date: Wed, 27 Sep 2023 01:09:03 +0900 [thread overview] Message-ID: <20230926160903.62924-1-masahiroy@kernel.org> (raw) The 32-bit ARM kernel stops working if the kernel grows to the point where veneers for __get_user_* are created. AAPCS32 [1] states, "Register r12 (IP) may be used by a linker as a scratch register between a routine and any subroutine it calls. It can also be used within a routine to hold intermediate values between subroutine calls." However, bl instructions buried within the inline asm are unpredictable for compilers; hence, "ip" must be added to the clobber list. This becomes critical when veneers for __get_user_* are created because veneers use the ip register since commit 02e541db0540 ("ARM: 8323/1: force linker to use PIC veneers"). [1]: https://github.com/ARM-software/abi-aa/blob/2023Q1/aapcs32/aapcs32.rst Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> --- KernelVersion: v6.6-rc1 arch/arm/include/asm/uaccess.h | 14 ++------------ 1 file changed, 2 insertions(+), 12 deletions(-) diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h index bb5c81823117..c28f5ec21e41 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -109,16 +109,6 @@ extern int __get_user_64t_1(void *); extern int __get_user_64t_2(void *); extern int __get_user_64t_4(void *); -#define __GUP_CLOBBER_1 "lr", "cc" -#ifdef CONFIG_CPU_USE_DOMAINS -#define __GUP_CLOBBER_2 "ip", "lr", "cc" -#else -#define __GUP_CLOBBER_2 "lr", "cc" -#endif -#define __GUP_CLOBBER_4 "lr", "cc" -#define __GUP_CLOBBER_32t_8 "lr", "cc" -#define __GUP_CLOBBER_8 "lr", "cc" - #define __get_user_x(__r2, __p, __e, __l, __s) \ __asm__ __volatile__ ( \ __asmeq("%0", "r0") __asmeq("%1", "r2") \ @@ -126,7 +116,7 @@ extern int __get_user_64t_4(void *); "bl __get_user_" #__s \ : "=&r" (__e), "=r" (__r2) \ : "0" (__p), "r" (__l) \ - : __GUP_CLOBBER_##__s) + : "ip", "lr", "cc") /* narrowing a double-word get into a single 32bit word register: */ #ifdef __ARMEB__ @@ -148,7 +138,7 @@ extern int __get_user_64t_4(void *); "bl __get_user_64t_" #__s \ : "=&r" (__e), "=r" (__r2) \ : "0" (__p), "r" (__l) \ - : __GUP_CLOBBER_##__s) + : "ip", "lr", "cc") #else #define __get_user_x_64t __get_user_x #endif -- 2.39.2 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2023-09-26 16:09 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-09-26 16:09 Masahiro Yamada [this message] 2023-09-26 16:09 ` [PATCH] ARM: fix get_user() broken with veneer Masahiro Yamada -- strict thread matches above, loose matches on Subject: below -- 2023-09-25 11:00 Masahiro Yamada 2023-09-25 11:00 ` Masahiro Yamada 2023-09-26 11:37 ` Ard Biesheuvel 2023-09-26 11:37 ` Ard Biesheuvel 2023-09-26 14:26 ` Masahiro Yamada 2023-09-26 14:26 ` Masahiro Yamada 2023-09-26 15:09 ` Ard Biesheuvel 2023-09-26 15:09 ` Ard Biesheuvel
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