libc/src/setjmp/x86_64/longjmp.cpp

   1 //===-- Implementation of longjmp -----------------------------------------===//
   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/setjmp/longjmp.h"
  10 #include "src/__support/common.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(void, longjmp, (__jmp_buf * buf, int val)) {
  19   register __UINT64_TYPE__ rbx __asm__("rbx");
  20   register __UINT64_TYPE__ rbp __asm__("rbp");
  21   register __UINT64_TYPE__ r12 __asm__("r12");
  22   register __UINT64_TYPE__ r13 __asm__("r13");
  23   register __UINT64_TYPE__ r14 __asm__("r14");
  24   register __UINT64_TYPE__ r15 __asm__("r15");
  25   register __UINT64_TYPE__ rsp __asm__("rsp");
  26   register __UINT64_TYPE__ rax __asm__("rax");
  27
  28   // ABI requires that the return value should be stored in rax. So, we store
  29   // |val| in rax. Note that this has to happen before we restore the registers
  30   // from values in |buf|. Otherwise, once rsp and rbp are updated, we cannot
  31   // read |val|.
  32   val = val == 0 ? 1 : val;
  33   LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(rax) : "m"(val) :);
  34   LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(rbx) : "m"(buf->rbx) :);
  35   LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(rbp) : "m"(buf->rbp) :);
  36   LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(r12) : "m"(buf->r12) :);
  37   LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(r13) : "m"(buf->r13) :);
  38   LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(r14) : "m"(buf->r14) :);
  39   LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(r15) : "m"(buf->r15) :);
  40   LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(rsp) : "m"(buf->rsp) :);
  41   LIBC_INLINE_ASM("jmp *%0\n\t" : : "m"(buf->rip));
  42 }
  43
  44 } // namespace LIBC_NAMESPACE