From ec6347bb43395cb92126788a1a5b25302543f815 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 5 Oct 2020 20:40:16 -0700 Subject: x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user, kernel}() 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 wrote: > > On Thu, Apr 30, 2020 at 6:21 PM Dan Williams 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 Signed-off-by: Borislav Petkov Reviewed-by: Tony Luck Acked-by: Michael Ellerman Cc: 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 --- include/linux/string.h | 9 +-------- include/linux/uaccess.h | 13 +++++++++++++ include/linux/uio.h | 10 +++++----- 3 files changed, 19 insertions(+), 13 deletions(-) (limited to 'include/linux') diff --git a/include/linux/string.h b/include/linux/string.h index 9b7a0632e87a..b1f3894a0a3e 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -161,20 +161,13 @@ extern int bcmp(const void *,const void *,__kernel_size_t); #ifndef __HAVE_ARCH_MEMCHR extern void * memchr(const void *,int,__kernel_size_t); #endif -#ifndef __HAVE_ARCH_MEMCPY_MCSAFE -static inline __must_check unsigned long memcpy_mcsafe(void *dst, - const void *src, size_t cnt) -{ - memcpy(dst, src, cnt); - return 0; -} -#endif #ifndef __HAVE_ARCH_MEMCPY_FLUSHCACHE static inline void memcpy_flushcache(void *dst, const void *src, size_t cnt) { memcpy(dst, src, cnt); } #endif + void *memchr_inv(const void *s, int c, size_t n); char *strreplace(char *s, char old, char new); diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 94b285411659..1ae36bc8db35 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -179,6 +179,19 @@ copy_in_user(void __user *to, const void __user *from, unsigned long n) } #endif +#ifndef copy_mc_to_kernel +/* + * Without arch opt-in this generic copy_mc_to_kernel() will not handle + * #MC (or arch equivalent) during source read. + */ +static inline unsigned long __must_check +copy_mc_to_kernel(void *dst, const void *src, size_t cnt) +{ + memcpy(dst, src, cnt); + return 0; +} +#endif + static __always_inline void pagefault_disabled_inc(void) { current->pagefault_disabled++; diff --git a/include/linux/uio.h b/include/linux/uio.h index 3835a8a8e9ea..f14410c678bd 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -185,10 +185,10 @@ size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i); #define _copy_from_iter_flushcache _copy_from_iter_nocache #endif -#ifdef CONFIG_ARCH_HAS_UACCESS_MCSAFE -size_t _copy_to_iter_mcsafe(const void *addr, size_t bytes, struct iov_iter *i); +#ifdef CONFIG_ARCH_HAS_COPY_MC +size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i); #else -#define _copy_to_iter_mcsafe _copy_to_iter +#define _copy_mc_to_iter _copy_to_iter #endif static __always_inline __must_check @@ -201,12 +201,12 @@ size_t copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i) } static __always_inline __must_check -size_t copy_to_iter_mcsafe(void *addr, size_t bytes, struct iov_iter *i) +size_t copy_mc_to_iter(void *addr, size_t bytes, struct iov_iter *i) { if (unlikely(!check_copy_size(addr, bytes, true))) return 0; else - return _copy_to_iter_mcsafe(addr, bytes, i); + return _copy_mc_to_iter(addr, bytes, i); } size_t iov_iter_zero(size_t bytes, struct iov_iter *); -- cgit v1.2.3-71-gd317