projects / mirror_ubuntu-artful-kernel.git / blame
| Commit | Line | Data |
|---|---|---|
| ac0999a8 DW |
1 | /* SPDX-License-Identifier: GPL-2.0 */ |
| 2 | ||
| 3 | #ifndef __NOSPEC_BRANCH_H__ | |
| 4 | #define __NOSPEC_BRANCH_H__ | |
| 5 | ||
| 6 | #include <asm/alternative.h> | |
| 7 | #include <asm/alternative-asm.h> | |
| 8 | #include <asm/cpufeatures.h> | |
| 9 | ||
| 10 | #ifdef __ASSEMBLY__ | |
| 11 | ||
| 12 | /* | |
| 13 | * This should be used immediately before a retpoline alternative. It tells | |
| 14 | * objtool where the retpolines are so that it can make sense of the control | |
| 15 | * flow by just reading the original instruction(s) and ignoring the | |
| 16 | * alternatives. | |
| 17 | */ | |
| 18 | .macro ANNOTATE_NOSPEC_ALTERNATIVE | |
| 19 | .Lannotate_\@: | |
| 20 | .pushsection .discard.nospec | |
| 21 | .long .Lannotate_\@ - . | |
| 22 | .popsection | |
| 23 | .endm | |
| 24 | ||
| 25 | /* | |
| 26 | * These are the bare retpoline primitives for indirect jmp and call. | |
| 27 | * Do not use these directly; they only exist to make the ALTERNATIVE | |
| 28 | * invocation below less ugly. | |
| 29 | */ | |
| 30 | .macro RETPOLINE_JMP reg:req | |
| 31 | call .Ldo_rop_\@ | |
| 32 | .Lspec_trap_\@: | |
| 33 | pause | |
| 34 | jmp .Lspec_trap_\@ | |
| 35 | .Ldo_rop_\@: | |
| 36 | mov \reg, (%_ASM_SP) | |
| 37 | ret | |
| 38 | .endm | |
| 39 | ||
| 40 | /* | |
| 41 | * This is a wrapper around RETPOLINE_JMP so the called function in reg | |
| 42 | * returns to the instruction after the macro. | |
| 43 | */ | |
| 44 | .macro RETPOLINE_CALL reg:req | |
| 45 | jmp .Ldo_call_\@ | |
| 46 | .Ldo_retpoline_jmp_\@: | |
| 47 | RETPOLINE_JMP \reg | |
| 48 | .Ldo_call_\@: | |
| 49 | call .Ldo_retpoline_jmp_\@ | |
| 50 | .endm | |
| 51 | ||
| 52 | /* | |
| 53 | * JMP_NOSPEC and CALL_NOSPEC macros can be used instead of a simple | |
| 54 | * indirect jmp/call which may be susceptible to the Spectre variant 2 | |
| 55 | * attack. | |
| 56 | */ | |
| 57 | .macro JMP_NOSPEC reg:req | |
| 58 | #ifdef CONFIG_RETPOLINE | |
| 59 | ANNOTATE_NOSPEC_ALTERNATIVE | |
| 60 | ALTERNATIVE_2 __stringify(jmp *\reg), \ | |
| 61 | __stringify(RETPOLINE_JMP \reg), X86_FEATURE_RETPOLINE, \ | |
| 62 | __stringify(lfence; jmp *\reg), X86_FEATURE_RETPOLINE_AMD | |
| 63 | #else | |
| 64 | jmp *\reg | |
| 65 | #endif | |
| 66 | .endm | |
| 67 | ||
| 68 | .macro CALL_NOSPEC reg:req | |
| 69 | #ifdef CONFIG_RETPOLINE | |
| 70 | ANNOTATE_NOSPEC_ALTERNATIVE | |
| 71 | ALTERNATIVE_2 __stringify(call *\reg), \ | |
| 72 | __stringify(RETPOLINE_CALL \reg), X86_FEATURE_RETPOLINE,\ | |
| 73 | __stringify(lfence; call *\reg), X86_FEATURE_RETPOLINE_AMD | |
| 74 | #else | |
| 75 | call *\reg | |
| 76 | #endif | |
| 77 | .endm | |
| 78 | ||
| 79 | #else /* __ASSEMBLY__ */ | |
| 80 | ||
| 81 | #define ANNOTATE_NOSPEC_ALTERNATIVE \ | |
| 82 | "999:\n\t" \ | |
| 83 | ".pushsection .discard.nospec\n\t" \ | |
| 84 | ".long 999b - .\n\t" \ | |
| 85 | ".popsection\n\t" | |
| 86 | ||
| 87 | #if defined(CONFIG_X86_64) && defined(RETPOLINE) | |
| 88 | ||
| 89 | /* | |
| 90 | * Since the inline asm uses the %V modifier which is only in newer GCC, | |
| 91 | * the 64-bit one is dependent on RETPOLINE not CONFIG_RETPOLINE. | |
| 92 | */ | |
| 93 | # define CALL_NOSPEC \ | |
| 94 | ANNOTATE_NOSPEC_ALTERNATIVE \ | |
| 95 | ALTERNATIVE( \ | |
| 96 | "call *%[thunk_target]\n", \ | |
| 97 | "call __x86_indirect_thunk_%V[thunk_target]\n", \ | |
| 98 | X86_FEATURE_RETPOLINE) | |
| 99 | # define THUNK_TARGET(addr) [thunk_target] "r" (addr) | |
| 100 | ||
| 101 | #elif defined(CONFIG_X86_32) && defined(CONFIG_RETPOLINE) | |
| 102 | /* | |
| 103 | * For i386 we use the original ret-equivalent retpoline, because | |
| 104 | * otherwise we'll run out of registers. We don't care about CET | |
| 105 | * here, anyway. | |
| 106 | */ | |
| 107 | # define CALL_NOSPEC ALTERNATIVE("call *%[thunk_target]\n", \ | |
| 108 | " jmp 904f;\n" \ | |
| 109 | " .align 16\n" \ | |
| 110 | "901: call 903f;\n" \ | |
| 111 | "902: pause;\n" \ | |
| 112 | " jmp 902b;\n" \ | |
| 113 | " .align 16\n" \ | |
| 114 | "903: addl $4, %%esp;\n" \ | |
| 115 | " pushl %[thunk_target];\n" \ | |
| 116 | " ret;\n" \ | |
| 117 | " .align 16\n" \ | |
| 118 | "904: call 901b;\n", \ | |
| 119 | X86_FEATURE_RETPOLINE) | |
| 120 | ||
| 121 | # define THUNK_TARGET(addr) [thunk_target] "rm" (addr) | |
| 122 | #else /* No retpoline */ | |
| 123 | # define CALL_NOSPEC "call *%[thunk_target]\n" | |
| 124 | # define THUNK_TARGET(addr) [thunk_target] "rm" (addr) | |
| 125 | #endif | |
| 126 | ||
| 127 | #endif /* __ASSEMBLY__ */ | |
| 128 | #endif /* __NOSPEC_BRANCH_H__ */ |