1 //===-- Implementation of setjmp ------------------------------------------===// 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-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "src/__support/common.h" 10 #include "src/setjmp/setjmp_impl.h" 11 12 #if !defined(LIBC_TARGET_ARCH_IS_X86_64) 13 #error "Invalid file include" 14 #endif 15 16 namespace LIBC_NAMESPACE { 17 18 LLVM_LIBC_FUNCTION(int, setjmp, (__jmp_buf * buf)) { 19 register __UINT64_TYPE__ rbx __asm__("rbx"); 20 register __UINT64_TYPE__ r12 __asm__("r12"); 21 register __UINT64_TYPE__ r13 __asm__("r13"); 22 register __UINT64_TYPE__ r14 __asm__("r14"); 23 register __UINT64_TYPE__ r15 __asm__("r15"); 24 25 // We want to store the register values as is. So, we will suppress the 26 // compiler warnings about the uninitialized variables declared above. 27 #pragma GCC diagnostic push 28 #pragma GCC diagnostic ignored "-Wuninitialized" 29 LIBC_INLINE_ASM("mov %1, %0\n\t" : "=m"(buf->rbx) : "r"(rbx) :); 30 LIBC_INLINE_ASM("mov %1, %0\n\t" : "=m"(buf->r12) : "r"(r12) :); 31 LIBC_INLINE_ASM("mov %1, %0\n\t" : "=m"(buf->r13) : "r"(r13) :); 32 LIBC_INLINE_ASM("mov %1, %0\n\t" : "=m"(buf->r14) : "r"(r14) :); 33 LIBC_INLINE_ASM("mov %1, %0\n\t" : "=m"(buf->r15) : "r"(r15) :); 34 #pragma GCC diagnostic pop 35 36 // We want the rbp of the caller, which is what __builtin_frame_address(1) 37 // should return. But, compilers generate a warning that calling 38 // __builtin_frame_address with non-zero argument is unsafe. So, we use 39 // the knowledge of the x86_64 ABI to fetch the callers rbp. As per the ABI, 40 // the rbp of the caller is pushed on to the stack and then new top is saved 41 // in this function's rbp. So, we fetch it from location at which this 42 // functions's rbp is pointing. 43 buf->rbp = *reinterpret_cast<__UINTPTR_TYPE__ *>(__builtin_frame_address(0)); 44 45 // The callers stack address is exactly 2 pointer widths ahead of the current 46 // frame pointer - between the current frame pointer and the rsp of the caller 47 // are the return address (pushed by the x86_64 call instruction) and the 48 // previous stack pointer as required by the x86_64 ABI. 49 // The stack pointer is ahead because the stack grows down on x86_64. 50 buf->rsp = reinterpret_cast<__UINTPTR_TYPE__>(__builtin_frame_address(0)) + 51 sizeof(__UINTPTR_TYPE__) * 2; 52 buf->rip = reinterpret_cast<__UINTPTR_TYPE__>(__builtin_return_address(0)); 53 return 0; 54 } 55 56 } // namespace LIBC_NAMESPACE 57