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 --- drivers/nvdimm/claim.c | 2 +- drivers/nvdimm/pmem.c | 6 +++--- 2 files changed, 4 insertions(+), 4 deletions(-) (limited to 'drivers/nvdimm') diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c index 45964acba944..22d865ba6353 100644 --- a/drivers/nvdimm/claim.c +++ b/drivers/nvdimm/claim.c @@ -268,7 +268,7 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns, if (rw == READ) { if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align))) return -EIO; - if (memcpy_mcsafe(buf, nsio->addr + offset, size) != 0) + if (copy_mc_to_kernel(buf, nsio->addr + offset, size) != 0) return -EIO; return 0; } diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index fab29b514372..5c6939e004e2 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -125,7 +125,7 @@ static blk_status_t read_pmem(struct page *page, unsigned int off, while (len) { mem = kmap_atomic(page); chunk = min_t(unsigned int, len, PAGE_SIZE - off); - rem = memcpy_mcsafe(mem + off, pmem_addr, chunk); + rem = copy_mc_to_kernel(mem + off, pmem_addr, chunk); kunmap_atomic(mem); if (rem) return BLK_STS_IOERR; @@ -304,7 +304,7 @@ static long pmem_dax_direct_access(struct dax_device *dax_dev, /* * Use the 'no check' versions of copy_from_iter_flushcache() and - * copy_to_iter_mcsafe() to bypass HARDENED_USERCOPY overhead. Bounds + * copy_mc_to_iter() to bypass HARDENED_USERCOPY overhead. Bounds * checking, both file offset and device offset, is handled by * dax_iomap_actor() */ @@ -317,7 +317,7 @@ static size_t pmem_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, static size_t pmem_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr, size_t bytes, struct iov_iter *i) { - return _copy_to_iter_mcsafe(addr, bytes, i); + return _copy_mc_to_iter(addr, bytes, i); } static const struct dax_operations pmem_dax_ops = { -- cgit v1.2.3