LXR linux/arch/x86/lib/retpoline.S

   1/* SPDX-License-Identifier: GPL-2.0 */
   2
   3#include <linux/stringify.h>
   4#include <linux/linkage.h>
   5#include <asm/dwarf2.h>
   6#include <asm/cpufeatures.h>
   7#include <asm/alternative.h>
   8#include <asm/export.h>
   9#include <asm/nospec-branch.h>
  10#include <asm/unwind_hints.h>
  11#include <asm/frame.h>
  12
  13        .section .text.__x86.indirect_thunk
  14
  15.macro RETPOLINE reg
  16        ANNOTATE_INTRA_FUNCTION_CALL
  17        call    .Ldo_rop_\@
  18.Lspec_trap_\@:
  19        UNWIND_HINT_EMPTY
  20        pause
  21        lfence
  22        jmp .Lspec_trap_\@
  23.Ldo_rop_\@:
  24        mov     %\reg, (%_ASM_SP)
  25        UNWIND_HINT_FUNC
  26        ret
  27.endm
  28
  29.macro THUNK reg
  30
  31        .align 32
  32
  33SYM_FUNC_START(__x86_indirect_thunk_\reg)
  34
  35        ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \
  36                      __stringify(RETPOLINE \reg), X86_FEATURE_RETPOLINE, \
  37                      __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_AMD
  38
  39SYM_FUNC_END(__x86_indirect_thunk_\reg)
  40
  41.endm
  42
  43/*
  44 * This generates .altinstr_replacement symbols for use by objtool. They,
  45 * however, must not actually live in .altinstr_replacement since that will be
  46 * discarded after init, but module alternatives will also reference these
  47 * symbols.
  48 *
  49 * Their names matches the "__x86_indirect_" prefix to mark them as retpolines.
  50 */
  51.macro ALT_THUNK reg
  52
  53        .align 1
  54
  55SYM_FUNC_START_NOALIGN(__x86_indirect_alt_call_\reg)
  56        ANNOTATE_RETPOLINE_SAFE
  571:      call    *%\reg
  582:      .skip   5-(2b-1b), 0x90
  59SYM_FUNC_END(__x86_indirect_alt_call_\reg)
  60
  61STACK_FRAME_NON_STANDARD(__x86_indirect_alt_call_\reg)
  62
  63SYM_FUNC_START_NOALIGN(__x86_indirect_alt_jmp_\reg)
  64        ANNOTATE_RETPOLINE_SAFE
  651:      jmp     *%\reg
  662:      .skip   5-(2b-1b), 0x90
  67SYM_FUNC_END(__x86_indirect_alt_jmp_\reg)
  68
  69STACK_FRAME_NON_STANDARD(__x86_indirect_alt_jmp_\reg)
  70
  71.endm
  72
  73/*
  74 * Despite being an assembler file we can't just use .irp here
  75 * because __KSYM_DEPS__ only uses the C preprocessor and would
  76 * only see one instance of "__x86_indirect_thunk_\reg" rather
  77 * than one per register with the correct names. So we do it
  78 * the simple and nasty way...
  79 *
  80 * Worse, you can only have a single EXPORT_SYMBOL per line,
  81 * and CPP can't insert newlines, so we have to repeat everything
  82 * at least twice.
  83 */
  84
  85#define __EXPORT_THUNK(sym)     _ASM_NOKPROBE(sym); EXPORT_SYMBOL(sym)
  86#define EXPORT_THUNK(reg)       __EXPORT_THUNK(__x86_indirect_thunk_ ## reg)
  87
  88#undef GEN
  89#define GEN(reg) THUNK reg
  90#include <asm/GEN-for-each-reg.h>
  91
  92#undef GEN
  93#define GEN(reg) EXPORT_THUNK(reg)
  94#include <asm/GEN-for-each-reg.h>
  95
  96#undef GEN
  97#define GEN(reg) ALT_THUNK reg
  98#include <asm/GEN-for-each-reg.h>
  99
 100#undef GEN
 101#define GEN(reg) __EXPORT_THUNK(__x86_indirect_alt_call_ ## reg)
 102#include <asm/GEN-for-each-reg.h>
 103
 104#undef GEN
 105#define GEN(reg) __EXPORT_THUNK(__x86_indirect_alt_jmp_ ## reg)
 106#include <asm/GEN-for-each-reg.h>
 107