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x86/mce: Drop copyin special case for #MC 

Fixes to the iterator code to handle faults that are not on page
boundaries mean that the special case for machine check during copy from
user is no longer needed.

For a full list of those fixes, see the output of:

  git log --oneline v5.14 ^v5.13 -- lib/iov_iter.c

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210818002942.1607544-4-tony.luck@intel.com
This commit is contained in:
Tony Luck 2021-08-17 17:29:42 -07:00 committed by Borislav Petkov
parent a6e3cf70b7
commit 690658471b
1 changed files with 0 additions and 13 deletions
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13
arch/x86/lib/copy_user_64.S
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@ -234,24 +234,11 @@ EXPORT_SYMBOL(copy_user_enhanced_fast_string)
*/
SYM_CODE_START_LOCAL(.Lcopy_user_handle_tail)
movl %edx,%ecx
cmp $X86_TRAP_MC,%eax /* check if X86_TRAP_MC */
je 3f
1: rep movsb
2: mov %ecx,%eax
ASM_CLAC
ret
/*
* Return zero to pretend that this copy succeeded. This
* is counter-intuitive, but needed to prevent the code
* in lib/iov_iter.c from retrying and running back into
* the poison cache line again. The machine check handler
* will ensure that a SIGBUS is sent to the task.
*/
3: xorl %eax,%eax
ASM_CLAC
ret
_ASM_EXTABLE_CPY(1b, 2b)
SYM_CODE_END(.Lcopy_user_handle_tail)