From 60622d68227d6d71fdfba5fb39f7f3d44cdd8815 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Thu, 3 May 2018 17:06:21 -0700 Subject: [PATCH] x86/asm/memcpy_mcsafe: Return bytes remaining Machine check safe memory copies are currently deployed in the pmem driver whenever reading from persistent memory media, so that -EIO is returned rather than triggering a kernel panic. While this protects most pmem accesses, it is not complete in the filesystem-dax case. When filesystem-dax is enabled reads may bypass the block layer and the driver via dax_iomap_actor() and its usage of copy_to_iter(). In preparation for creating a copy_to_iter() variant that can handle machine checks, teach memcpy_mcsafe() to return the number of bytes remaining rather than -EFAULT when an exception occurs. Co-developed-by: Tony Luck Signed-off-by: Dan Williams Cc: Al Viro Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Tony Luck Cc: hch@lst.de Cc: linux-fsdevel@vger.kernel.org Cc: linux-nvdimm@lists.01.org Link: http://lkml.kernel.org/r/152539238119.31796.14318473522414462886.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/string_64.h | 8 +++++--- arch/x86/lib/memcpy_64.S | 20 ++++++++++++++------ drivers/nvdimm/claim.c | 3 ++- drivers/nvdimm/pmem.c | 6 +++--- include/linux/string.h | 4 ++-- 5 files changed, 26 insertions(+), 15 deletions(-) diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h index 4752f89..d33f92b 100644 --- a/arch/x86/include/asm/string_64.h +++ b/arch/x86/include/asm/string_64.h @@ -116,7 +116,8 @@ int strcmp(const char *cs, const char *ct); #endif #define __HAVE_ARCH_MEMCPY_MCSAFE 1 -__must_check int __memcpy_mcsafe(void *dst, const void *src, size_t cnt); +__must_check unsigned long __memcpy_mcsafe(void *dst, const void *src, + size_t cnt); DECLARE_STATIC_KEY_FALSE(mcsafe_key); /** @@ -131,9 +132,10 @@ DECLARE_STATIC_KEY_FALSE(mcsafe_key); * actually do machine check recovery. Everyone else can just * use memcpy(). * - * Return 0 for success, -EFAULT for fail + * Return 0 for success, or number of bytes not copied if there was an + * exception. */ -static __always_inline __must_check int +static __always_inline __must_check unsigned long memcpy_mcsafe(void *dst, const void *src, size_t cnt) { #ifdef CONFIG_X86_MCE diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S index 5709f3e..f01a883 100644 --- a/arch/x86/lib/memcpy_64.S +++ b/arch/x86/lib/memcpy_64.S @@ -252,14 +252,22 @@ ENDPROC(__memcpy_mcsafe) EXPORT_SYMBOL_GPL(__memcpy_mcsafe) .section .fixup, "ax" - /* Return -EFAULT for any failure */ -.L_memcpy_mcsafe_fail: - mov $-EFAULT, %rax + /* + * Return number of bytes not copied for any failure. Note that + * there is no "tail" handling since the source buffer is 8-byte + * aligned and poison is cacheline aligned. + */ +.E_read_words: + shll $3, %ecx +.E_leading_bytes: + addl %edx, %ecx +.E_trailing_bytes: + mov %ecx, %eax ret .previous - _ASM_EXTABLE_FAULT(.L_read_leading_bytes, .L_memcpy_mcsafe_fail) - _ASM_EXTABLE_FAULT(.L_read_words, .L_memcpy_mcsafe_fail) - _ASM_EXTABLE_FAULT(.L_read_trailing_bytes, .L_memcpy_mcsafe_fail) + _ASM_EXTABLE_FAULT(.L_read_leading_bytes, .E_leading_bytes) + _ASM_EXTABLE_FAULT(.L_read_words, .E_read_words) + _ASM_EXTABLE_FAULT(.L_read_trailing_bytes, .E_trailing_bytes) #endif diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c index 3085227..2e96b34 100644 --- a/drivers/nvdimm/claim.c +++ b/drivers/nvdimm/claim.c @@ -276,7 +276,8 @@ 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; - return memcpy_mcsafe(buf, nsio->addr + offset, size); + if (memcpy_mcsafe(buf, nsio->addr + offset, size) != 0) + return -EIO; } if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align))) { diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index 9d71492..e023d6a 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -101,15 +101,15 @@ static blk_status_t read_pmem(struct page *page, unsigned int off, void *pmem_addr, unsigned int len) { unsigned int chunk; - int rc; + unsigned long rem; void *mem; while (len) { mem = kmap_atomic(page); chunk = min_t(unsigned int, len, PAGE_SIZE); - rc = memcpy_mcsafe(mem + off, pmem_addr, chunk); + rem = memcpy_mcsafe(mem + off, pmem_addr, chunk); kunmap_atomic(mem); - if (rc) + if (rem) return BLK_STS_IOERR; len -= chunk; off = 0; diff --git a/include/linux/string.h b/include/linux/string.h index dd39a69..4a5a0eb 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -147,8 +147,8 @@ extern int memcmp(const void *,const void *,__kernel_size_t); extern void * memchr(const void *,int,__kernel_size_t); #endif #ifndef __HAVE_ARCH_MEMCPY_MCSAFE -static inline __must_check int memcpy_mcsafe(void *dst, const void *src, - size_t cnt) +static inline __must_check unsigned long memcpy_mcsafe(void *dst, + const void *src, size_t cnt) { memcpy(dst, src, cnt); return 0; -- 2.7.4