arch/x86/include/asm/gsseg.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 #ifndef _ASM_X86_GSSEG_H
   3 #define _ASM_X86_GSSEG_H
   4
   5 #include <linux/types.h>
   6
   7 #include <asm/asm.h>
   8 #include <asm/cpufeature.h>
   9 #include <asm/alternative.h>
  10 #include <asm/processor.h>
  11 #include <asm/nops.h>
  12
  13 #ifdef CONFIG_X86_64
  14
  15 extern asmlinkage void asm_load_gs_index(u16 selector);
  16
  17 /* Replace with "lkgs %di" once binutils support LKGS instruction */
  18 #define LKGS_DI _ASM_BYTES(0xf2,0x0f,0x00,0xf7)
  19
  20 static inline void native_lkgs(unsigned int selector)
  21 {
  22         u16 sel = selector;
  23         asm_inline volatile("1: " LKGS_DI
  24                             _ASM_EXTABLE_TYPE_REG(1b, 1b, EX_TYPE_ZERO_REG, %k[sel])
  25                             : [sel] "+D" (sel));
  26 }
  27
  28 static inline void native_load_gs_index(unsigned int selector)
  29 {
  30         if (cpu_feature_enabled(X86_FEATURE_LKGS)) {
  31                 native_lkgs(selector);
  32         } else {
  33                 unsigned long flags;
  34
  35                 local_irq_save(flags);
  36                 asm_load_gs_index(selector);
  37                 local_irq_restore(flags);
  38         }
  39 }
  40
  41 #endif /* CONFIG_X86_64 */
  42
  43 static inline void __init lkgs_init(void)
  44 {
  45 #ifdef CONFIG_PARAVIRT_XXL
  46 #ifdef CONFIG_X86_64
  47         if (cpu_feature_enabled(X86_FEATURE_LKGS))
  48                 pv_ops.cpu.load_gs_index = native_lkgs;
  49 #endif
  50 #endif
  51 }
  52
  53 #ifndef CONFIG_PARAVIRT_XXL
  54
  55 static inline void load_gs_index(unsigned int selector)
  56 {
  57 #ifdef CONFIG_X86_64
  58         native_load_gs_index(selector);
  59 #else
  60         loadsegment(gs, selector);
  61 #endif
  62 }
  63
  64 #endif /* CONFIG_PARAVIRT_XXL */
  65
  66 #endif /* _ASM_X86_GSSEG_H */