From 17bc43367fc2a720400d21c745db641c654c1e6b Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Fri, 17 Apr 2020 17:08:52 +0000 Subject: [PATCH] powerpc/uaccess: Implement unsafe_copy_to_user() as a simple loop At the time being, unsafe_copy_to_user() is based on raw_copy_to_user() which calls __copy_tofrom_user(). __copy_tofrom_user() is a big optimised function to copy big amount of data. It aligns destinations to cache line in order to use dcbz instruction. Today unsafe_copy_to_user() is called only from filldir(). It is used to mainly copy small amount of data like filenames, so __copy_tofrom_user() is not fit. Also, unsafe_copy_to_user() is used within user_access_begin/end sections. In those section, it is preferable to not call functions. Rewrite unsafe_copy_to_user() as a macro that uses __put_user_goto(). We first perform a loop of long, then we finish with necessary complements. unsafe_copy_to_user() might be used in the near future to copy fixed-size data, like pt_regs structs during signal processing. Having it as a macro allows GCC to optimise it for instead when it knows the size in advance, it can unloop loops, drop complements when the size is a multiple of longs, etc ... Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/fe952112c29bf6a0a2778c9e6bbb4f4afd2c4258.1587143308.git.christophe.leroy@c-s.fr --- arch/powerpc/include/asm/uaccess.h | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index 3f30a1dbc198..42b6c44e36a7 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -535,7 +535,26 @@ static __must_check inline bool user_access_begin(const void __user *ptr, size_t #define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0) #define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e) #define unsafe_put_user(x, p, e) __put_user_goto(x, p, e) + #define unsafe_copy_to_user(d, s, l, e) \ - unsafe_op_wrap(raw_copy_to_user_allowed(d, s, l), e) +do { \ + u8 __user *_dst = (u8 __user *)(d); \ + const u8 *_src = (const u8 *)(s); \ + size_t _len = (l); \ + int _i; \ + \ + for (_i = 0; _i < (_len & ~(sizeof(long) - 1)); _i += sizeof(long)) \ + __put_user_goto(*(long*)(_src + _i), (long __user *)(_dst + _i), e);\ + if (IS_ENABLED(CONFIG_PPC64) && (_len & 4)) { \ + __put_user_goto(*(u32*)(_src + _i), (u32 __user *)(_dst + _i), e); \ + _i += 4; \ + } \ + if (_len & 2) { \ + __put_user_goto(*(u16*)(_src + _i), (u16 __user *)(_dst + _i), e); \ + _i += 2; \ + } \ + if (_len & 1) \ + __put_user_goto(*(u8*)(_src + _i), (u8 __user *)(_dst + _i), e);\ +} while (0) #endif /* _ARCH_POWERPC_UACCESS_H */