libc/src/setjmp/x86_64/setjmp.cpp

//===-- Implementation of setjmp ------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// We use naked functions to avoid compiler-generated prologue and epilogue.
// Despite GCC documentation listing this as an unsupported case for extended
// asm, the generated code is not wrong as we only pass in constant operands
// to extended asm.
// See https://github.com/llvm/llvm-project/issues/137055 for related remarks.

#include "hdr/offsetof_macros.h"
#include "src/__support/common.h"
#include "src/__support/macros/config.h"
#include "src/setjmp/setjmp_impl.h"

#if !defined(LIBC_TARGET_ARCH_IS_X86)
#error "Invalid file include"
#endif

namespace LIBC_NAMESPACE_DECL {

#ifdef __i386__
[[gnu::naked]]
LLVM_LIBC_FUNCTION(int, setjmp, (jmp_buf buf)) {
  asm(R"(
      mov 4(%%esp), %%eax

      mov %%ebx, %c[ebx](%%eax)
      mov %%esi, %c[esi](%%eax)
      mov %%edi, %c[edi](%%eax)
      mov %%ebp, %c[ebp](%%eax)

      lea 4(%%esp), %%ecx
      mov %%ecx, %c[esp](%%eax)

      mov (%%esp), %%ecx
      mov %%ecx, %c[eip](%%eax)

      xorl %%eax, %%eax
      retl)" ::[ebx] "i"(offsetof(__jmp_buf, ebx)),
      [esi] "i"(offsetof(__jmp_buf, esi)), [edi] "i"(offsetof(__jmp_buf, edi)),
      [ebp] "i"(offsetof(__jmp_buf, ebp)), [esp] "i"(offsetof(__jmp_buf, esp)),
      [eip] "i"(offsetof(__jmp_buf, eip))
      : "eax", "ecx");
}
#else
[[gnu::naked]]
LLVM_LIBC_FUNCTION(int, setjmp, (jmp_buf buf)) {
  asm(R"(
      mov %%rbx, %c[rbx](%%rdi)
      mov %%rbp, %c[rbp](%%rdi)
      mov %%r12, %c[r12](%%rdi)
      mov %%r13, %c[r13](%%rdi)
      mov %%r14, %c[r14](%%rdi)
      mov %%r15, %c[r15](%%rdi)

      lea 8(%%rsp), %%rax
      mov %%rax, %c[rsp](%%rdi)

      mov (%%rsp), %%rax
      mov %%rax, %c[rip](%%rdi)

      xorl %%eax, %%eax
      retq)" ::[rbx] "i"(offsetof(__jmp_buf, rbx)),
      [rbp] "i"(offsetof(__jmp_buf, rbp)), [r12] "i"(offsetof(__jmp_buf, r12)),
      [r13] "i"(offsetof(__jmp_buf, r13)), [r14] "i"(offsetof(__jmp_buf, r14)),
      [r15] "i"(offsetof(__jmp_buf, r15)), [rsp] "i"(offsetof(__jmp_buf, rsp)),
      [rip] "i"(offsetof(__jmp_buf, rip))
      : "rax");
}
#endif

} // namespace LIBC_NAMESPACE_DECL