| 1 | //===-- Implementation of longjmp for AArch64 -----------------------------===// |
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| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | |
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| 9 | #include "src/setjmp/longjmp.h" |
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| 10 | #include "src/__support/common.h" |
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| 11 | #include "src/__support/macros/config.h" |
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| 12 | |
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| 13 | namespace LIBC_NAMESPACE_DECL { |
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| 14 | |
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| 15 | // TODO: if MTE stack tagging is in use (-fsanitize=memtag-stack), we need to |
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| 16 | // iterate over the region between the old and new values of sp, using STG or |
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| 17 | // ST2G instructions to clear the memory tags on the invalidated region of the |
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| 18 | // stack. But this requires a means of finding out that we're in that mode, and |
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| 19 | // as far as I can see there isn't currently a predefined macro for that. |
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| 20 | // |
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| 21 | // (__ARM_FEATURE_MEMORY_TAGGING only indicates whether the target architecture |
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| 22 | // supports the MTE instructions, not whether the compiler is configured to use |
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| 23 | // them.) |
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| 24 | |
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| 25 | [[gnu::naked]] LLVM_LIBC_FUNCTION(void, longjmp, |
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| 26 | ([[maybe_unused]] jmp_buf buf, |
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| 27 | [[maybe_unused]] int val)) { |
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| 28 | // If BTI branch protection is in use, the compiler will automatically insert |
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| 29 | // a BTI here, so we don't need to make any extra effort to do so. |
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| 30 | |
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| 31 | // If PAC branch protection is in use, there's no need to sign the return |
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| 32 | // address at the start of longjmp, because we're not going to use it anyway! |
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| 33 | |
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| 34 | asm( |
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| 35 | // Reload the callee-saved GPRs, including fp and lr. |
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| 36 | R"( |
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| 37 | ldp x19, x20, [x0, #0*16] |
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| 38 | ldp x21, x22, [x0, #1*16] |
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| 39 | ldp x23, x24, [x0, #2*16] |
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| 40 | ldp x25, x26, [x0, #3*16] |
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| 41 | ldp x27, x28, [x0, #4*16] |
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| 42 | ldp x29, x30, [x0, #5*16] |
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| 43 | )" |
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| 44 | |
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| 45 | #if LIBC_COPT_SETJMP_AARCH64_RESTORE_PLATFORM_REGISTER |
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| 46 | // Reload the stack pointer, and the platform register x18. |
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| 47 | R"( |
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| 48 | ldp x2, x18, [x0, #6*16] |
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| 49 | mov sp, x2 |
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| 50 | )" |
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| 51 | #else |
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| 52 | // Reload just the stack pointer. |
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| 53 | R"( |
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| 54 | ldr x2, [x0, #6*16] |
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| 55 | mov sp, x2 |
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| 56 | )" |
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| 57 | #endif |
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| 58 | |
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| 59 | #if __ARM_FP |
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| 60 | // Reload the callee-saved FP registers. |
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| 61 | R"( |
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| 62 | ldp d8, d9, [x0, #7*16] |
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| 63 | ldp d10, d11, [x0, #8*16] |
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| 64 | ldp d12, d13, [x0, #9*16] |
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| 65 | ldp d14, d15, [x0, #10*16] |
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| 66 | )" |
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| 67 | #endif |
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| 68 | |
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| 69 | // Calculate the return value. |
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| 70 | R"( |
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| 71 | cmp w1, #0 |
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| 72 | cinc w0, w1, eq |
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| 73 | )" |
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| 74 | |
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| 75 | #if __ARM_FEATURE_PAC_DEFAULT & 1 |
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| 76 | // Authenticate the return address using the PAC A key. |
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| 77 | R"( |
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| 78 | autiasp |
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| 79 | )" |
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| 80 | #elif __ARM_FEATURE_PAC_DEFAULT & 2 |
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| 81 | // Authenticate the return address using the PAC B key. |
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| 82 | R"( |
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| 83 | autibsp |
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| 84 | )" |
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| 85 | #endif |
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| 86 | |
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| 87 | R"( |
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| 88 | ret |
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| 89 | )" ); |
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| 90 | } |
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| 91 | |
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| 92 | } // namespace LIBC_NAMESPACE_DECL |
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| 93 | |
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