libc/src/setjmp/aarch64/setjmp.cpp

   1 //===-- Implementation of setjmp for AArch64 ------------------------------===//
   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/__support/macros/config.h"
  11 #include "src/setjmp/setjmp_impl.h"
  12
  13 namespace LIBC_NAMESPACE_DECL {
  14
  15 [[gnu::naked]] LLVM_LIBC_FUNCTION(int, setjmp, ([[maybe_unused]] jmp_buf buf)) {
  16   // If BTI branch protection is in use, the compiler will automatically insert
  17   // a BTI here, so we don't need to make any extra effort to do so.
  18
  19   asm(
  20 #if __ARM_FEATURE_PAC_DEFAULT & 1
  21       // Sign the return address using the PAC A key.
  22       R"(
  23         paciasp
  24       )"
  25 #elif __ARM_FEATURE_PAC_DEFAULT & 2
  26       // Sign the return address using the PAC B key.
  27       R"(
  28         pacibsp
  29       )"
  30 #endif
  31
  32       // Store all the callee-saved GPRs, including fp (x29) and also lr (x30).
  33       // Of course lr isn't normally callee-saved (the call instruction itself
  34       // can't help clobbering it), but we certainly need to save it for this
  35       // purpose.
  36       R"(
  37         stp x19, x20, [x0,  #0*16]
  38         stp x21, x22, [x0,  #1*16]
  39         stp x23, x24, [x0,  #2*16]
  40         stp x25, x26, [x0,  #3*16]
  41         stp x27, x28, [x0,  #4*16]
  42         stp x29, x30, [x0,  #5*16]
  43       )"
  44
  45 #if LIBC_COPT_SETJMP_AARCH64_RESTORE_PLATFORM_REGISTER
  46       // Store the stack pointer, and the platform register x18.
  47       R"(
  48         add x1, sp, #0
  49         stp x1, x18,  [x0,  #6*16]
  50       )"
  51 #else
  52       // Store just the stack pointer.
  53       R"(
  54         add x1, sp, #0
  55         str x1,       [x0,  #6*16]
  56       )"
  57 #endif
  58
  59 #if __ARM_FP
  60       // Store the callee-saved FP registers. AAPCS64 only requires the low 64
  61       // bits of v8-v15 to be preserved, i.e. each of d8,...,d15.
  62       R"(
  63         stp d8,  d9,  [x0,  #7*16]
  64         stp d10, d11, [x0,  #8*16]
  65         stp d12, d13, [x0,  #9*16]
  66         stp d14, d15, [x0, #10*16]
  67       )"
  68 #endif
  69
  70       // Set up return value of zero.
  71       R"(
  72         mov x0, #0
  73       )"
  74
  75 #if (__ARM_FEATURE_PAC_DEFAULT & 7) == 5
  76       // Authenticate the return address using the PAC A key, since the
  77       // compilation options ask for PAC protection even on leaf functions.
  78       R"(
  79         autiasp
  80       )"
  81 #elif (__ARM_FEATURE_PAC_DEFAULT & 7) == 6
  82       // Same, but using the PAC B key.
  83       R"(
  84         autibsp
  85       )"
  86 #endif
  87
  88       R"(
  89         ret
  90       )");
  91 }
  92
  93 } // namespace LIBC_NAMESPACE_DECL