From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- arch/x86/kernel/static_call.c | 212 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 212 insertions(+) create mode 100644 arch/x86/kernel/static_call.c (limited to 'arch/x86/kernel/static_call.c') diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c new file mode 100644 index 000000000..3fbb49168 --- /dev/null +++ b/arch/x86/kernel/static_call.c @@ -0,0 +1,212 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include + +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 */ + JCC = 4, +}; + +/* + * ud1 %esp, %ecx - a 3 byte #UD that is unique to trampolines, chosen such + * that there is no false-positive trampoline identification while also being a + * speculation stop. + */ +static const u8 tramp_ud[] = { 0x0f, 0xb9, 0xcc }; + +/* + * cs cs cs xorl %eax, %eax - a single 5 byte instruction that clears %[er]ax + */ +static const u8 xor5rax[] = { 0x2e, 0x2e, 0x2e, 0x31, 0xc0 }; + +static const u8 retinsn[] = { RET_INSN_OPCODE, 0xcc, 0xcc, 0xcc, 0xcc }; + +static u8 __is_Jcc(u8 *insn) /* Jcc.d32 */ +{ + u8 ret = 0; + + if (insn[0] == 0x0f) { + u8 tmp = insn[1]; + if ((tmp & 0xf0) == 0x80) + ret = tmp; + } + + return ret; +} + +extern void __static_call_return(void); + +asm (".global __static_call_return\n\t" + ".type __static_call_return, @function\n\t" + "__static_call_return:\n\t" + ANNOTATE_NOENDBR + ANNOTATE_RETPOLINE_SAFE + "ret; int3\n\t" + ".size __static_call_return, . - __static_call_return \n\t"); + +static void __ref __static_call_transform(void *insn, enum insn_type type, + void *func, bool modinit) +{ + const void *emulate = NULL; + int size = CALL_INSN_SIZE; + const void *code; + u8 op, buf[6]; + + if ((type == JMP || type == RET) && (op = __is_Jcc(insn))) + type = JCC; + + 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: + if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) + code = text_gen_insn(JMP32_INSN_OPCODE, insn, &__x86_return_thunk); + else + code = &retinsn; + break; + + case JCC: + if (!func) { + func = __static_call_return; + if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) + func = __x86_return_thunk; + } + + buf[0] = 0x0f; + __text_gen_insn(buf+1, op, insn+1, func, 5); + code = buf; + size = 6; + + break; + } + + if (memcmp(insn, code, size) == 0) + return; + + if (system_state == SYSTEM_BOOTING || modinit) + return text_poke_early(insn, code, size); + + text_poke_bp(insn, code, size, emulate); +} + +static void __static_call_validate(u8 *insn, bool tail, bool tramp) +{ + u8 opcode = insn[0]; + + if (tramp && memcmp(insn+5, tramp_ud, 3)) { + pr_err("trampoline signature fail"); + BUG(); + } + + if (tail) { + if (opcode == JMP32_INSN_OPCODE || + opcode == RET_INSN_OPCODE || + __is_Jcc(insn)) + 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. + */ + pr_err("unexpected static_call insn opcode 0x%x at %pS\n", opcode, insn); + BUG(); +} + +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, true); + __static_call_transform(tramp, __sc_insn(!func, true), func, false); + } + + if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site) { + __static_call_validate(site, tail, false); + __static_call_transform(site, __sc_insn(!func, tail), func, false); + } + + mutex_unlock(&text_mutex); +} +EXPORT_SYMBOL_GPL(arch_static_call_transform); + +#ifdef CONFIG_RETHUNK +/* + * This is called by apply_returns() to fix up static call trampolines, + * specifically ARCH_DEFINE_STATIC_CALL_NULL_TRAMP which is recorded as + * having a return trampoline. + * + * The problem is that static_call() is available before determining + * X86_FEATURE_RETHUNK and, by implication, running alternatives. + * + * This means that __static_call_transform() above can have overwritten the + * return trampoline and we now need to fix things up to be consistent. + */ +bool __static_call_fixup(void *tramp, u8 op, void *dest) +{ + unsigned long addr = (unsigned long)tramp; + /* + * Not all .return_sites are a static_call trampoline (most are not). + * Check if the 3 bytes after the return are still kernel text, if not, + * then this definitely is not a trampoline and we need not worry + * further. + * + * This avoids the memcmp() below tripping over pagefaults etc.. + */ + if (((addr >> PAGE_SHIFT) != ((addr + 7) >> PAGE_SHIFT)) && + !kernel_text_address(addr + 7)) + return false; + + if (memcmp(tramp+5, tramp_ud, 3)) { + /* Not a trampoline site, not our problem. */ + return false; + } + + mutex_lock(&text_mutex); + if (op == RET_INSN_OPCODE || dest == &__x86_return_thunk) + __static_call_transform(tramp, RET, NULL, true); + mutex_unlock(&text_mutex); + + return true; +} +#endif -- cgit v1.2.3