93 lines · cpp
1//===-- Implementation of longjmp for AArch64 -----------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#include "src/setjmp/longjmp.h"10#include "src/__support/common.h"11#include "src/__support/macros/config.h"12 13namespace LIBC_NAMESPACE_DECL {14 15// TODO: if MTE stack tagging is in use (-fsanitize=memtag-stack), we need to16// iterate over the region between the old and new values of sp, using STG or17// ST2G instructions to clear the memory tags on the invalidated region of the18// stack. But this requires a means of finding out that we're in that mode, and19// as far as I can see there isn't currently a predefined macro for that.20//21// (__ARM_FEATURE_MEMORY_TAGGING only indicates whether the target architecture22// supports the MTE instructions, not whether the compiler is configured to use23// them.)24 25[[gnu::naked]] LLVM_LIBC_FUNCTION(void, longjmp,26 ([[maybe_unused]] jmp_buf buf,27 [[maybe_unused]] int val)) {28 // If BTI branch protection is in use, the compiler will automatically insert29 // a BTI here, so we don't need to make any extra effort to do so.30 31 // If PAC branch protection is in use, there's no need to sign the return32 // address at the start of longjmp, because we're not going to use it anyway!33 34 asm(35 // Reload the callee-saved GPRs, including fp and lr.36 R"(37 ldp x19, x20, [x0, #0*16]38 ldp x21, x22, [x0, #1*16]39 ldp x23, x24, [x0, #2*16]40 ldp x25, x26, [x0, #3*16]41 ldp x27, x28, [x0, #4*16]42 ldp x29, x30, [x0, #5*16]43 )"44 45#if LIBC_COPT_SETJMP_AARCH64_RESTORE_PLATFORM_REGISTER46 // Reload the stack pointer, and the platform register x18.47 R"(48 ldp x2, x18, [x0, #6*16]49 mov sp, x250 )"51#else52 // Reload just the stack pointer.53 R"(54 ldr x2, [x0, #6*16]55 mov sp, x256 )"57#endif58 59#if __ARM_FP60 // Reload the callee-saved FP registers.61 R"(62 ldp d8, d9, [x0, #7*16]63 ldp d10, d11, [x0, #8*16]64 ldp d12, d13, [x0, #9*16]65 ldp d14, d15, [x0, #10*16]66 )"67#endif68 69 // Calculate the return value.70 R"(71 cmp w1, #072 cinc w0, w1, eq73 )"74 75#if __ARM_FEATURE_PAC_DEFAULT & 176 // Authenticate the return address using the PAC A key.77 R"(78 autiasp79 )"80#elif __ARM_FEATURE_PAC_DEFAULT & 281 // Authenticate the return address using the PAC B key.82 R"(83 autibsp84 )"85#endif86 87 R"(88 ret89 )");90}91 92} // namespace LIBC_NAMESPACE_DECL93