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| author | Masahiro Yamada <masahiroy@kernel.org> | 2023-09-26 19:09:03 +0300 |
|---|---|---|
| committer | Russell King (Oracle) <rmk+kernel@armlinux.org.uk> | 2023-10-05 18:16:19 +0300 |
| commit | 24d3ba0a7b44c1617c27f5045eecc4f34752ab03 (patch) | |
| tree | 67ed448fc283c37f262d3fe29f81bd689f2d7439 | |
| parent | 399da29ff5eb3f675c71423bec4cf2208f218576 (diff) | |
| download | linux-24d3ba0a7b44c1617c27f5045eecc4f34752ab03.tar.xz | |
ARM: 9324/1: fix get_user() broken with veneer
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>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
| -rw-r--r-- | arch/arm/include/asm/uaccess.h | 14 |
1 files 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 |