Extract memcpy and memset functions from copy_user_generic() and __clear_user(). They can be used as inline memcpy and memset instead of the GCC builtins whenever necessary. LASS requires them to handle text_poke. Originally-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Link: https://lore.kernel.org/all/20241029184840.GJ14555@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> --- arch/x86/include/asm/string.h | 46 +++++++++++++++++++++++++++++++ arch/x86/include/asm/uaccess_64.h | 38 +++++++------------------ arch/x86/lib/clear_page_64.S | 10 +++++-- 3 files changed, 64 insertions(+), 30 deletions(-) diff --git a/arch/x86/include/asm/string.h b/arch/x86/include/asm/string.h index c3c2c1914d65..5cd0f18a431f 100644 --- a/arch/x86/include/asm/string.h +++ b/arch/x86/include/asm/string.h @@ -1,6 +1,52 @@ /* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_STRING_H +#define _ASM_X86_STRING_H + +#include <asm/asm.h> +#include <asm/alternative.h> +#include <asm/cpufeatures.h> + #ifdef CONFIG_X86_32 # include <asm/string_32.h> #else # include <asm/string_64.h> #endif + +#ifdef CONFIG_X86_64 +#define ALT_64(orig, alt, feat) ALTERNATIVE(orig, alt, feat) +#else +#define ALT_64(orig, alt, feat) orig "\n" +#endif + +static __always_inline void *__inline_memcpy(void *to, const void *from, size_t len) +{ + void *ret = to; + + asm volatile("1:\n\t" + ALT_64("rep movsb", + "call rep_movs_alternative", ALT_NOT(X86_FEATURE_FSRM)) + "2:\n\t" + _ASM_EXTABLE_UA(1b, 2b) + :"+c" (len), "+D" (to), "+S" (from), ASM_CALL_CONSTRAINT + : : "memory", _ASM_AX); + + return ret + len; +} + +static __always_inline void *__inline_memset(void *addr, int v, size_t len) +{ + void *ret = addr; + + asm volatile("1:\n\t" + ALT_64("rep stosb", + "call rep_stos_alternative", ALT_NOT(X86_FEATURE_FSRM)) + "2:\n\t" + _ASM_EXTABLE_UA(1b, 2b) + : "+c" (len), "+D" (addr), ASM_CALL_CONSTRAINT + : "a" ((uint8_t)v) + : "memory", _ASM_SI); + + return ret + len; +} + +#endif /* _ASM_X86_STRING_H */ diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h index c8a5ae35c871..eb531e13e659 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -13,6 +13,7 @@ #include <asm/page.h> #include <asm/percpu.h> #include <asm/runtime-const.h> +#include <asm/string.h> /* * Virtual variable: there's no actual backing store for this, @@ -118,21 +119,12 @@ rep_movs_alternative(void *to, const void *from, unsigned len); static __always_inline __must_check unsigned long copy_user_generic(void *to, const void *from, unsigned long len) { + void *ret; + stac(); - /* - * If CPU has FSRM feature, use 'rep movs'. - * Otherwise, use rep_movs_alternative. - */ - asm volatile( - "1:\n\t" - ALTERNATIVE("rep movsb", - "call rep_movs_alternative", ALT_NOT(X86_FEATURE_FSRM)) - "2:\n" - _ASM_EXTABLE_UA(1b, 2b) - :"+c" (len), "+D" (to), "+S" (from), ASM_CALL_CONSTRAINT - : : "memory", "rax"); + ret = __inline_memcpy(to, from, len); clac(); - return len; + return ret - to; } static __always_inline __must_check unsigned long @@ -178,25 +170,15 @@ rep_stos_alternative(void __user *addr, unsigned long len); static __always_inline __must_check unsigned long __clear_user(void __user *addr, unsigned long size) { + void *ptr = (__force void *)addr; + void *ret; + might_fault(); stac(); - - /* - * No memory constraint because it doesn't change any memory gcc - * knows about. - */ - asm volatile( - "1:\n\t" - ALTERNATIVE("rep stosb", - "call rep_stos_alternative", ALT_NOT(X86_FEATURE_FSRS)) - "2:\n" - _ASM_EXTABLE_UA(1b, 2b) - : "+c" (size), "+D" (addr), ASM_CALL_CONSTRAINT - : "a" (0)); - + ret = __inline_memset(ptr, 0, size); clac(); - return size; + return ret - ptr; } static __always_inline unsigned long clear_user(void __user *to, unsigned long n) diff --git a/arch/x86/lib/clear_page_64.S b/arch/x86/lib/clear_page_64.S index a508e4a8c66a..ca94828def62 100644 --- a/arch/x86/lib/clear_page_64.S +++ b/arch/x86/lib/clear_page_64.S @@ -55,17 +55,23 @@ SYM_FUNC_END(clear_page_erms) EXPORT_SYMBOL_GPL(clear_page_erms) /* - * Default clear user-space. + * Default memset. * Input: * rdi destination + * rsi scratch * rcx count - * rax is zero + * al is value * * Output: * rcx: uncleared bytes or 0 if successful. */ SYM_FUNC_START(rep_stos_alternative) ANNOTATE_NOENDBR + + movzbq %al, %rsi + movabs $0x0101010101010101, %rax + mulq %rsi + cmpq $64,%rcx jae .Lunrolled -- 2.47.2
