1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/static_call.h> 3 #include <linux/memory.h> 4 #include <linux/bug.h> 5 #include <asm/text-patching.h> 6 7 enum insn_type { 8 CALL = 0, /* site call */ 9 NOP = 1, /* site cond-call */ 10 JMP = 2, /* tramp / site tail-call */ 11 RET = 3, /* tramp / site cond-tail-call */ 12 }; 13 14 static void __ref __static_call_transform(void *insn, enum insn_type type, void *func) 15 { 16 int size = CALL_INSN_SIZE; 17 const void *code; 18 19 switch (type) { 20 case CALL: 21 code = text_gen_insn(CALL_INSN_OPCODE, insn, func); 22 break; 23 24 case NOP: 25 code = ideal_nops[NOP_ATOMIC5]; 26 break; 27 28 case JMP: 29 code = text_gen_insn(JMP32_INSN_OPCODE, insn, func); 30 break; 31 32 case RET: 33 code = text_gen_insn(RET_INSN_OPCODE, insn, func); 34 size = RET_INSN_SIZE; 35 break; 36 } 37 38 if (memcmp(insn, code, size) == 0) 39 return; 40 41 if (unlikely(system_state == SYSTEM_BOOTING)) 42 return text_poke_early(insn, code, size); 43 44 text_poke_bp(insn, code, size, NULL); 45 } 46 47 static void __static_call_validate(void *insn, bool tail) 48 { 49 u8 opcode = *(u8 *)insn; 50 51 if (tail) { 52 if (opcode == JMP32_INSN_OPCODE || 53 opcode == RET_INSN_OPCODE) 54 return; 55 } else { 56 if (opcode == CALL_INSN_OPCODE || 57 !memcmp(insn, ideal_nops[NOP_ATOMIC5], 5)) 58 return; 59 } 60 61 /* 62 * If we ever trigger this, our text is corrupt, we'll probably not live long. 63 */ 64 WARN_ONCE(1, "unexpected static_call insn opcode 0x%x at %pS\n", opcode, insn); 65 } 66 67 static inline enum insn_type __sc_insn(bool null, bool tail) 68 { 69 /* 70 * Encode the following table without branches: 71 * 72 * tail null insn 73 * -----+-------+------ 74 * 0 | 0 | CALL 75 * 0 | 1 | NOP 76 * 1 | 0 | JMP 77 * 1 | 1 | RET 78 */ 79 return 2*tail + null; 80 } 81 82 void arch_static_call_transform(void *site, void *tramp, void *func, bool tail) 83 { 84 mutex_lock(&text_mutex); 85 86 if (tramp) { 87 __static_call_validate(tramp, true); 88 __static_call_transform(tramp, __sc_insn(!func, true), func); 89 } 90 91 if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site) { 92 __static_call_validate(site, tail); 93 __static_call_transform(site, __sc_insn(!func, tail), func); 94 } 95 96 mutex_unlock(&text_mutex); 97 } 98 EXPORT_SYMBOL_GPL(arch_static_call_transform); 99