Edit File: make_x86_64_sysv_elf_gas.S
/* Copyright Oliver Kowalke 2009. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) */ /**************************************************************************************** * * * ---------------------------------------------------------------------------------- * * | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | * * ---------------------------------------------------------------------------------- * * | 0x0 | 0x4 | 0x8 | 0xc | 0x10 | 0x14 | 0x18 | 0x1c | * * ---------------------------------------------------------------------------------- * * | fc_mxcsr|fc_x87_cw| guard | R12 | R13 | * * ---------------------------------------------------------------------------------- * * ---------------------------------------------------------------------------------- * * | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | * * ---------------------------------------------------------------------------------- * * | 0x20 | 0x24 | 0x28 | 0x2c | 0x30 | 0x34 | 0x38 | 0x3c | * * ---------------------------------------------------------------------------------- * * | R14 | R15 | RBX | RBP | * * ---------------------------------------------------------------------------------- * * ---------------------------------------------------------------------------------- * * | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | * * ---------------------------------------------------------------------------------- * * | 0x40 | 0x44 | | * * ---------------------------------------------------------------------------------- * * | RIP | | * * ---------------------------------------------------------------------------------- * * * ****************************************************************************************/ # if defined __CET__ # include <cet.h> # define SHSTK_ENABLED (__CET__ & 0x2) # define BOOST_CONTEXT_SHADOW_STACK (SHSTK_ENABLED && SHADOW_STACK_SYSCALL) # else # define _CET_ENDBR # endif .file "make_x86_64_sysv_elf_gas.S" .text .globl make_fcontext .type make_fcontext,@function .align 16 make_fcontext: _CET_ENDBR #if BOOST_CONTEXT_SHADOW_STACK /* the new shadow stack pointer (SSP) */ movq -0x8(%rdi), %r9 #endif /* first arg of make_fcontext() == top of context-stack */ movq %rdi, %rax /* shift address in RAX to lower 16 byte boundary */ andq $-16, %rax /* reserve space for context-data on context-stack */ /* on context-function entry: (RSP -0x8) % 16 == 0 */ leaq -0x48(%rax), %rax /* third arg of make_fcontext() == address of context-function */ /* stored in RBX */ movq %rdx, 0x30(%rax) /* save MMX control- and status-word */ stmxcsr (%rax) /* save x87 control-word */ fnstcw 0x4(%rax) #if defined(BOOST_CONTEXT_TLS_STACK_PROTECTOR) /* save stack guard */ movq %fs:0x28, %rcx /* read stack guard from TLS record */ movq %rcx, 0x8(%rsp) /* save stack guard */ #endif /* compute abs address of label trampoline */ leaq trampoline(%rip), %rcx /* save address of trampoline as return-address for context-function */ /* will be entered after calling jump_fcontext() first time */ movq %rcx, 0x40(%rax) /* compute abs address of label finish */ leaq finish(%rip), %rcx /* save address of finish as return-address for context-function */ /* will be entered after context-function returns */ movq %rcx, 0x38(%rax) #if BOOST_CONTEXT_SHADOW_STACK /* Populate the shadow stack and normal stack */ /* get original SSP */ rdsspq %r8 /* restore new shadow stack */ rstorssp -0x8(%r9) /* save the restore token on the original shadow stack */ saveprevssp /* push the address of "jmp trampoline" to the new shadow stack */ /* as well as the stack */ call 1f jmp trampoline 1: /* save address of "jmp trampoline" as return-address */ /* for context-function */ pop 0x38(%rax) /* Get the new SSP. */ rdsspq %r9 /* restore original shadow stack */ rstorssp -0x8(%r8) /* save the restore token on the new shadow stack. */ saveprevssp /* reserve space for the new SSP */ leaq -0x8(%rax), %rax /* save the new SSP to this fcontext */ movq %r9, (%rax) #endif ret /* return pointer to context-data */ trampoline: _CET_ENDBR /* store return address on stack */ /* fix stack alignment */ #if BOOST_CONTEXT_SHADOW_STACK /* save address of "jmp *%rbp" as return-address */ /* on stack and shadow stack */ call 2f jmp *%rbp 2: #else push %rbp #endif /* jump to context-function */ jmp *%rbx finish: _CET_ENDBR /* exit code is zero */ xorq %rdi, %rdi /* exit application */ call _exit@PLT hlt .size make_fcontext,.-make_fcontext /* Mark that we don't need executable stack. */ .section .note.GNU-stack,"",%progbits