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ec6347bb43
In reaction to a proposal to introduce a memcpy_mcsafe_fast() implementation Linus points out that memcpy_mcsafe() is poorly named relative to communicating the scope of the interface. Specifically what addresses are valid to pass as source, destination, and what faults / exceptions are handled. Of particular concern is that even though x86 might be able to handle the semantics of copy_mc_to_user() with its common copy_user_generic() implementation other archs likely need / want an explicit path for this case: On Fri, May 1, 2020 at 11:28 AM Linus Torvalds <torvalds@linux-foundation.org> wrote: > > On Thu, Apr 30, 2020 at 6:21 PM Dan Williams <dan.j.williams@intel.com> wrote: > > > > However now I see that copy_user_generic() works for the wrong reason. > > It works because the exception on the source address due to poison > > looks no different than a write fault on the user address to the > > caller, it's still just a short copy. So it makes copy_to_user() work > > for the wrong reason relative to the name. > > Right. > > And it won't work that way on other architectures. On x86, we have a > generic function that can take faults on either side, and we use it > for both cases (and for the "in_user" case too), but that's an > artifact of the architecture oddity. > > In fact, it's probably wrong even on x86 - because it can hide bugs - > but writing those things is painful enough that everybody prefers > having just one function. Replace a single top-level memcpy_mcsafe() with either copy_mc_to_user(), or copy_mc_to_kernel(). Introduce an x86 copy_mc_fragile() name as the rename for the low-level x86 implementation formerly named memcpy_mcsafe(). It is used as the slow / careful backend that is supplanted by a fast copy_mc_generic() in a follow-on patch. One side-effect of this reorganization is that separating copy_mc_64.S to its own file means that perf no longer needs to track dependencies for its memcpy_64.S benchmarks. [ bp: Massage a bit. ] Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Tony Luck <tony.luck@intel.com> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Cc: <stable@vger.kernel.org> Link: http://lore.kernel.org/r/CAHk-=wjSqtXAqfUJxFtWNwmguFASTgB0dz1dT3V-78Quiezqbg@mail.gmail.com Link: https://lkml.kernel.org/r/160195561680.2163339.11574962055305783722.stgit@dwillia2-desk3.amr.corp.intel.com
110 lines
2.8 KiB
C
110 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_STRING_64_H
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#define _ASM_X86_STRING_64_H
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#ifdef __KERNEL__
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#include <linux/jump_label.h>
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/* Written 2002 by Andi Kleen */
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/* Even with __builtin_ the compiler may decide to use the out of line
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function. */
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#define __HAVE_ARCH_MEMCPY 1
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extern void *memcpy(void *to, const void *from, size_t len);
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extern void *__memcpy(void *to, const void *from, size_t len);
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#define __HAVE_ARCH_MEMSET
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void *memset(void *s, int c, size_t n);
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void *__memset(void *s, int c, size_t n);
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#define __HAVE_ARCH_MEMSET16
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static inline void *memset16(uint16_t *s, uint16_t v, size_t n)
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{
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long d0, d1;
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asm volatile("rep\n\t"
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"stosw"
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: "=&c" (d0), "=&D" (d1)
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: "a" (v), "1" (s), "0" (n)
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: "memory");
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return s;
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}
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#define __HAVE_ARCH_MEMSET32
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static inline void *memset32(uint32_t *s, uint32_t v, size_t n)
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{
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long d0, d1;
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asm volatile("rep\n\t"
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"stosl"
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: "=&c" (d0), "=&D" (d1)
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: "a" (v), "1" (s), "0" (n)
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: "memory");
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return s;
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}
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#define __HAVE_ARCH_MEMSET64
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static inline void *memset64(uint64_t *s, uint64_t v, size_t n)
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{
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long d0, d1;
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asm volatile("rep\n\t"
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"stosq"
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: "=&c" (d0), "=&D" (d1)
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: "a" (v), "1" (s), "0" (n)
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: "memory");
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return s;
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}
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#define __HAVE_ARCH_MEMMOVE
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void *memmove(void *dest, const void *src, size_t count);
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void *__memmove(void *dest, const void *src, size_t count);
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int memcmp(const void *cs, const void *ct, size_t count);
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size_t strlen(const char *s);
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char *strcpy(char *dest, const char *src);
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char *strcat(char *dest, const char *src);
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int strcmp(const char *cs, const char *ct);
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#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
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/*
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* For files that not instrumented (e.g. mm/slub.c) we
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* should use not instrumented version of mem* functions.
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*/
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#undef memcpy
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#define memcpy(dst, src, len) __memcpy(dst, src, len)
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#define memmove(dst, src, len) __memmove(dst, src, len)
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#define memset(s, c, n) __memset(s, c, n)
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#ifndef __NO_FORTIFY
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#define __NO_FORTIFY /* FORTIFY_SOURCE uses __builtin_memcpy, etc. */
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#endif
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#endif
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#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
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#define __HAVE_ARCH_MEMCPY_FLUSHCACHE 1
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void __memcpy_flushcache(void *dst, const void *src, size_t cnt);
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static __always_inline void memcpy_flushcache(void *dst, const void *src, size_t cnt)
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{
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if (__builtin_constant_p(cnt)) {
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switch (cnt) {
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case 4:
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asm ("movntil %1, %0" : "=m"(*(u32 *)dst) : "r"(*(u32 *)src));
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return;
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case 8:
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asm ("movntiq %1, %0" : "=m"(*(u64 *)dst) : "r"(*(u64 *)src));
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return;
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case 16:
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asm ("movntiq %1, %0" : "=m"(*(u64 *)dst) : "r"(*(u64 *)src));
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asm ("movntiq %1, %0" : "=m"(*(u64 *)(dst + 8)) : "r"(*(u64 *)(src + 8)));
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return;
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}
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}
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__memcpy_flushcache(dst, src, cnt);
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}
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#endif
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#endif /* __KERNEL__ */
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#endif /* _ASM_X86_STRING_64_H */
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