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Merge tag 'x86_asm_for_v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull x86 asm updates from Borislav Petkov:
 "Two asm wrapper fixes:

   - Use XORL instead of XORQ to avoid a REX prefix and save some bytes
     in the .fixup section, by Uros Bizjak.

   - Replace __force_order dummy variable with a memory clobber to fix
     LLVM requiring a definition for former and to prevent memory
     accesses from still being cached/reordered, by Arvind Sankar"

* tag 'x86_asm_for_v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/asm: Replace __force_order with a memory clobber
  x86/uaccess: Use XORL %0,%0 in __get_user_asm()
This commit is contained in:
Linus Torvalds
2020-10-13 13:36:07 -07:00
parent 7cd4ecd917 aa5cacdc29
commit 029f56db6a
4 changed files with 18 additions and 25 deletions
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4
arch/x86/kernel/cpu/common.c
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@@ -360,7 +360,7 @@ void native_write_cr0(unsigned long val)
unsigned long bits_missing = 0;
set_register:
asm volatile("mov %0,%%cr0": "+r" (val), "+m" (__force_order));
asm volatile("mov %0,%%cr0": "+r" (val) : : "memory");
if (static_branch_likely(&cr_pinning)) {
if (unlikely((val & X86_CR0_WP) != X86_CR0_WP)) {
@@ -379,7 +379,7 @@ void native_write_cr4(unsigned long val)
unsigned long bits_changed = 0;
set_register:
asm volatile("mov %0,%%cr4": "+r" (val), "+m" (cr4_pinned_bits));
asm volatile("mov %0,%%cr4": "+r" (val) : : "memory");
if (static_branch_likely(&cr_pinning)) {
if (unlikely((val & cr4_pinned_mask) != cr4_pinned_bits)) {