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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 <tony.luck@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony Luck <tony.luck@intel.com> 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 <mingo@kernel.org>
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@ -116,7 +116,8 @@ int strcmp(const char *cs, const char *ct);
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#endif
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#define __HAVE_ARCH_MEMCPY_MCSAFE 1
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__must_check int __memcpy_mcsafe(void *dst, const void *src, size_t cnt);
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__must_check unsigned long __memcpy_mcsafe(void *dst, const void *src,
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size_t cnt);
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DECLARE_STATIC_KEY_FALSE(mcsafe_key);
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/**
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@ -131,9 +132,10 @@ DECLARE_STATIC_KEY_FALSE(mcsafe_key);
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* actually do machine check recovery. Everyone else can just
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* use memcpy().
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*
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* Return 0 for success, -EFAULT for fail
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* Return 0 for success, or number of bytes not copied if there was an
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* exception.
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*/
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static __always_inline __must_check int
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static __always_inline __must_check unsigned long
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memcpy_mcsafe(void *dst, const void *src, size_t cnt)
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{
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#ifdef CONFIG_X86_MCE
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@ -252,14 +252,22 @@ ENDPROC(__memcpy_mcsafe)
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EXPORT_SYMBOL_GPL(__memcpy_mcsafe)
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.section .fixup, "ax"
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/* Return -EFAULT for any failure */
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.L_memcpy_mcsafe_fail:
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mov $-EFAULT, %rax
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/*
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* Return number of bytes not copied for any failure. Note that
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* there is no "tail" handling since the source buffer is 8-byte
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* aligned and poison is cacheline aligned.
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*/
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.E_read_words:
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shll $3, %ecx
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.E_leading_bytes:
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addl %edx, %ecx
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.E_trailing_bytes:
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mov %ecx, %eax
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ret
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.previous
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_ASM_EXTABLE_FAULT(.L_read_leading_bytes, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_read_words, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_read_trailing_bytes, .L_memcpy_mcsafe_fail)
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_ASM_EXTABLE_FAULT(.L_read_leading_bytes, .E_leading_bytes)
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_ASM_EXTABLE_FAULT(.L_read_words, .E_read_words)
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_ASM_EXTABLE_FAULT(.L_read_trailing_bytes, .E_trailing_bytes)
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#endif
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@ -276,7 +276,8 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
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if (rw == READ) {
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if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align)))
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return -EIO;
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return memcpy_mcsafe(buf, nsio->addr + offset, size);
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if (memcpy_mcsafe(buf, nsio->addr + offset, size) != 0)
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return -EIO;
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}
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if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align))) {
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@ -101,15 +101,15 @@ static blk_status_t read_pmem(struct page *page, unsigned int off,
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void *pmem_addr, unsigned int len)
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{
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unsigned int chunk;
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int rc;
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unsigned long rem;
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void *mem;
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while (len) {
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mem = kmap_atomic(page);
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chunk = min_t(unsigned int, len, PAGE_SIZE);
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rc = memcpy_mcsafe(mem + off, pmem_addr, chunk);
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rem = memcpy_mcsafe(mem + off, pmem_addr, chunk);
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kunmap_atomic(mem);
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if (rc)
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if (rem)
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return BLK_STS_IOERR;
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len -= chunk;
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off = 0;
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@ -147,8 +147,8 @@ extern int memcmp(const void *,const void *,__kernel_size_t);
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extern void * memchr(const void *,int,__kernel_size_t);
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#endif
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#ifndef __HAVE_ARCH_MEMCPY_MCSAFE
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static inline __must_check int memcpy_mcsafe(void *dst, const void *src,
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size_t cnt)
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static inline __must_check unsigned long memcpy_mcsafe(void *dst,
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const void *src, size_t cnt)
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{
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memcpy(dst, src, cnt);
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return 0;
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