| 1 | //===-- Implementation of setjmp ------------------------------------------===// |
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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/__support/common.h" |
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| 10 | #include "src/setjmp/setjmp_impl.h" |
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| 11 | |
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| 12 | #if !defined(LIBC_TARGET_ARCH_IS_X86_64) |
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| 13 | #error "Invalid file include" |
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| 14 | #endif |
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| 15 | |
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| 16 | namespace LIBC_NAMESPACE { |
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| 17 | |
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| 18 | LLVM_LIBC_FUNCTION(int, setjmp, (__jmp_buf * buf)) { |
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| 19 | register __UINT64_TYPE__ rbx __asm__("rbx" ); |
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| 20 | register __UINT64_TYPE__ r12 __asm__("r12" ); |
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| 21 | register __UINT64_TYPE__ r13 __asm__("r13" ); |
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| 22 | register __UINT64_TYPE__ r14 __asm__("r14" ); |
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| 23 | register __UINT64_TYPE__ r15 __asm__("r15" ); |
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| 24 | |
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| 25 | // We want to store the register values as is. So, we will suppress the |
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| 26 | // compiler warnings about the uninitialized variables declared above. |
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| 27 | #pragma GCC diagnostic push |
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| 28 | #pragma GCC diagnostic ignored "-Wuninitialized" |
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| 29 | LIBC_INLINE_ASM("mov %1, %0\n\t" : "=m" (buf->rbx) : "r" (rbx) :); |
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| 30 | LIBC_INLINE_ASM("mov %1, %0\n\t" : "=m" (buf->r12) : "r" (r12) :); |
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| 31 | LIBC_INLINE_ASM("mov %1, %0\n\t" : "=m" (buf->r13) : "r" (r13) :); |
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| 32 | LIBC_INLINE_ASM("mov %1, %0\n\t" : "=m" (buf->r14) : "r" (r14) :); |
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| 33 | LIBC_INLINE_ASM("mov %1, %0\n\t" : "=m" (buf->r15) : "r" (r15) :); |
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| 34 | #pragma GCC diagnostic pop |
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| 35 | |
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| 36 | // We want the rbp of the caller, which is what __builtin_frame_address(1) |
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| 37 | // should return. But, compilers generate a warning that calling |
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| 38 | // __builtin_frame_address with non-zero argument is unsafe. So, we use |
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| 39 | // the knowledge of the x86_64 ABI to fetch the callers rbp. As per the ABI, |
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| 40 | // the rbp of the caller is pushed on to the stack and then new top is saved |
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| 41 | // in this function's rbp. So, we fetch it from location at which this |
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| 42 | // functions's rbp is pointing. |
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| 43 | buf->rbp = *reinterpret_cast<__UINTPTR_TYPE__ *>(__builtin_frame_address(0)); |
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| 44 | |
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| 45 | // The callers stack address is exactly 2 pointer widths ahead of the current |
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| 46 | // frame pointer - between the current frame pointer and the rsp of the caller |
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| 47 | // are the return address (pushed by the x86_64 call instruction) and the |
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| 48 | // previous stack pointer as required by the x86_64 ABI. |
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| 49 | // The stack pointer is ahead because the stack grows down on x86_64. |
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| 50 | buf->rsp = reinterpret_cast<__UINTPTR_TYPE__>(__builtin_frame_address(0)) + |
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| 51 | sizeof(__UINTPTR_TYPE__) * 2; |
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| 52 | buf->rip = reinterpret_cast<__UINTPTR_TYPE__>(__builtin_return_address(0)); |
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| 53 | return 0; |
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| 54 | } |
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| 55 | |
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| 56 | } // namespace LIBC_NAMESPACE |
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| 57 | |
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