Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 | // SPDX-License-Identifier: GPL-2.0 #include <linux/static_call.h> #include <linux/memory.h> #include <linux/bug.h> #include <asm/text-patching.h> enum insn_type { CALL = 0, /* site call */ NOP = 1, /* site cond-call */ JMP = 2, /* tramp / site tail-call */ RET = 3, /* tramp / site cond-tail-call */ }; /* * data16 data16 xorq %rax, %rax - a single 5 byte instruction that clears %rax * The REX.W cancels the effect of any data16. */ static const u8 xor5rax[] = { 0x66, 0x66, 0x48, 0x31, 0xc0 }; static void __ref __static_call_transform(void *insn, enum insn_type type, void *func) { const void *emulate = NULL; int size = CALL_INSN_SIZE; const void *code; switch (type) { case CALL: code = text_gen_insn(CALL_INSN_OPCODE, insn, func); if (func == &__static_call_return0) { emulate = code; code = &xor5rax; } break; case NOP: code = x86_nops[5]; break; case JMP: code = text_gen_insn(JMP32_INSN_OPCODE, insn, func); break; case RET: code = text_gen_insn(RET_INSN_OPCODE, insn, func); size = RET_INSN_SIZE; break; } if (memcmp(insn, code, size) == 0) return; if (unlikely(system_state == SYSTEM_BOOTING)) return text_poke_early(insn, code, size); text_poke_bp(insn, code, size, emulate); } static void __static_call_validate(void *insn, bool tail) { u8 opcode = *(u8 *)insn; if (tail) { if (opcode == JMP32_INSN_OPCODE || opcode == RET_INSN_OPCODE) return; } else { if (opcode == CALL_INSN_OPCODE || !memcmp(insn, x86_nops[5], 5) || !memcmp(insn, xor5rax, 5)) return; } /* * If we ever trigger this, our text is corrupt, we'll probably not live long. */ WARN_ONCE(1, "unexpected static_call insn opcode 0x%x at %pS\n", opcode, insn); } static inline enum insn_type __sc_insn(bool null, bool tail) { /* * Encode the following table without branches: * * tail null insn * -----+-------+------ * 0 | 0 | CALL * 0 | 1 | NOP * 1 | 0 | JMP * 1 | 1 | RET */ return 2*tail + null; } void arch_static_call_transform(void *site, void *tramp, void *func, bool tail) { mutex_lock(&text_mutex); if (tramp) { __static_call_validate(tramp, true); __static_call_transform(tramp, __sc_insn(!func, true), func); } if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site) { __static_call_validate(site, tail); __static_call_transform(site, __sc_insn(!func, tail), func); } mutex_unlock(&text_mutex); } EXPORT_SYMBOL_GPL(arch_static_call_transform); |