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Dan Williams
60622d6822
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>
274 lines
5.2 KiB
ArmAsm
274 lines
5.2 KiB
ArmAsm
/* Copyright 2002 Andi Kleen */
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#include <linux/linkage.h>
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#include <asm/errno.h>
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#include <asm/cpufeatures.h>
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#include <asm/alternative-asm.h>
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#include <asm/export.h>
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/*
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* We build a jump to memcpy_orig by default which gets NOPped out on
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* the majority of x86 CPUs which set REP_GOOD. In addition, CPUs which
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* have the enhanced REP MOVSB/STOSB feature (ERMS), change those NOPs
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* to a jmp to memcpy_erms which does the REP; MOVSB mem copy.
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*/
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.weak memcpy
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/*
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* memcpy - Copy a memory block.
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*
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* Input:
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* rdi destination
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* rsi source
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* rdx count
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*
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* Output:
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* rax original destination
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*/
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ENTRY(__memcpy)
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ENTRY(memcpy)
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ALTERNATIVE_2 "jmp memcpy_orig", "", X86_FEATURE_REP_GOOD, \
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"jmp memcpy_erms", X86_FEATURE_ERMS
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movq %rdi, %rax
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movq %rdx, %rcx
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shrq $3, %rcx
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andl $7, %edx
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rep movsq
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movl %edx, %ecx
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rep movsb
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ret
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ENDPROC(memcpy)
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ENDPROC(__memcpy)
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EXPORT_SYMBOL(memcpy)
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EXPORT_SYMBOL(__memcpy)
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/*
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* memcpy_erms() - enhanced fast string memcpy. This is faster and
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* simpler than memcpy. Use memcpy_erms when possible.
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*/
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ENTRY(memcpy_erms)
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movq %rdi, %rax
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movq %rdx, %rcx
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rep movsb
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ret
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ENDPROC(memcpy_erms)
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ENTRY(memcpy_orig)
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movq %rdi, %rax
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cmpq $0x20, %rdx
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jb .Lhandle_tail
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/*
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* We check whether memory false dependence could occur,
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* then jump to corresponding copy mode.
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*/
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cmp %dil, %sil
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jl .Lcopy_backward
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subq $0x20, %rdx
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.Lcopy_forward_loop:
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subq $0x20, %rdx
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/*
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* Move in blocks of 4x8 bytes:
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*/
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movq 0*8(%rsi), %r8
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movq 1*8(%rsi), %r9
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movq 2*8(%rsi), %r10
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movq 3*8(%rsi), %r11
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leaq 4*8(%rsi), %rsi
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movq %r8, 0*8(%rdi)
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movq %r9, 1*8(%rdi)
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movq %r10, 2*8(%rdi)
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movq %r11, 3*8(%rdi)
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leaq 4*8(%rdi), %rdi
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jae .Lcopy_forward_loop
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addl $0x20, %edx
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jmp .Lhandle_tail
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.Lcopy_backward:
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/*
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* Calculate copy position to tail.
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*/
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addq %rdx, %rsi
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addq %rdx, %rdi
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subq $0x20, %rdx
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/*
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* At most 3 ALU operations in one cycle,
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* so append NOPS in the same 16 bytes trunk.
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*/
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.p2align 4
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.Lcopy_backward_loop:
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subq $0x20, %rdx
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movq -1*8(%rsi), %r8
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movq -2*8(%rsi), %r9
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movq -3*8(%rsi), %r10
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movq -4*8(%rsi), %r11
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leaq -4*8(%rsi), %rsi
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movq %r8, -1*8(%rdi)
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movq %r9, -2*8(%rdi)
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movq %r10, -3*8(%rdi)
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movq %r11, -4*8(%rdi)
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leaq -4*8(%rdi), %rdi
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jae .Lcopy_backward_loop
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/*
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* Calculate copy position to head.
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*/
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addl $0x20, %edx
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subq %rdx, %rsi
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subq %rdx, %rdi
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.Lhandle_tail:
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cmpl $16, %edx
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jb .Lless_16bytes
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/*
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* Move data from 16 bytes to 31 bytes.
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*/
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movq 0*8(%rsi), %r8
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movq 1*8(%rsi), %r9
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movq -2*8(%rsi, %rdx), %r10
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movq -1*8(%rsi, %rdx), %r11
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movq %r8, 0*8(%rdi)
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movq %r9, 1*8(%rdi)
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movq %r10, -2*8(%rdi, %rdx)
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movq %r11, -1*8(%rdi, %rdx)
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retq
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.p2align 4
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.Lless_16bytes:
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cmpl $8, %edx
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jb .Lless_8bytes
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/*
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* Move data from 8 bytes to 15 bytes.
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*/
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movq 0*8(%rsi), %r8
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movq -1*8(%rsi, %rdx), %r9
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movq %r8, 0*8(%rdi)
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movq %r9, -1*8(%rdi, %rdx)
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retq
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.p2align 4
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.Lless_8bytes:
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cmpl $4, %edx
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jb .Lless_3bytes
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/*
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* Move data from 4 bytes to 7 bytes.
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*/
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movl (%rsi), %ecx
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movl -4(%rsi, %rdx), %r8d
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movl %ecx, (%rdi)
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movl %r8d, -4(%rdi, %rdx)
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retq
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.p2align 4
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.Lless_3bytes:
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subl $1, %edx
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jb .Lend
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/*
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* Move data from 1 bytes to 3 bytes.
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*/
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movzbl (%rsi), %ecx
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jz .Lstore_1byte
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movzbq 1(%rsi), %r8
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movzbq (%rsi, %rdx), %r9
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movb %r8b, 1(%rdi)
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movb %r9b, (%rdi, %rdx)
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.Lstore_1byte:
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movb %cl, (%rdi)
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.Lend:
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retq
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ENDPROC(memcpy_orig)
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#ifndef CONFIG_UML
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/*
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* __memcpy_mcsafe - memory copy with machine check exception handling
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* Note that we only catch machine checks when reading the source addresses.
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* Writes to target are posted and don't generate machine checks.
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*/
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ENTRY(__memcpy_mcsafe)
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cmpl $8, %edx
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/* Less than 8 bytes? Go to byte copy loop */
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jb .L_no_whole_words
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/* Check for bad alignment of source */
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testl $7, %esi
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/* Already aligned */
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jz .L_8byte_aligned
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/* Copy one byte at a time until source is 8-byte aligned */
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movl %esi, %ecx
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andl $7, %ecx
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subl $8, %ecx
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negl %ecx
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subl %ecx, %edx
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.L_read_leading_bytes:
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movb (%rsi), %al
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.L_write_leading_bytes:
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movb %al, (%rdi)
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incq %rsi
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incq %rdi
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decl %ecx
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jnz .L_read_leading_bytes
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.L_8byte_aligned:
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movl %edx, %ecx
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andl $7, %edx
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shrl $3, %ecx
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jz .L_no_whole_words
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.L_read_words:
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movq (%rsi), %r8
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.L_write_words:
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movq %r8, (%rdi)
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addq $8, %rsi
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addq $8, %rdi
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decl %ecx
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jnz .L_read_words
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/* Any trailing bytes? */
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.L_no_whole_words:
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andl %edx, %edx
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jz .L_done_memcpy_trap
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/* Copy trailing bytes */
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movl %edx, %ecx
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.L_read_trailing_bytes:
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movb (%rsi), %al
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.L_write_trailing_bytes:
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movb %al, (%rdi)
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incq %rsi
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incq %rdi
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decl %ecx
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jnz .L_read_trailing_bytes
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/* Copy successful. Return zero */
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.L_done_memcpy_trap:
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xorq %rax, %rax
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ret
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ENDPROC(__memcpy_mcsafe)
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EXPORT_SYMBOL_GPL(__memcpy_mcsafe)
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.section .fixup, "ax"
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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, .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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