libucontext/arch/x86_64/startcontext.S

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/*
* Copyright (c) 2018 Ariadne Conill <ariadne@dereferenced.org>
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*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* This software is provided 'as is' and without any warranty, express or
* implied. In no event shall the authors be liable for any damages arising
* from the use of this software.
*/
.globl __start_context;
__start_context:
/* get the proper context into position and test for NULL */
movq %rbx, %rsp
movq (%rsp), %rdi
testq %rdi, %rdi
/* if we have no linked context, lets get out of here */
je no_linked_context
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/* call setcontext to switch to the linked context */
call __setcontext@plt
movq %rax, %rdi
no_linked_context:
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/* we are returning into a null context, it seems, so maybe we should exit */
call exit@plt
/* something is really hosed, call hlt to force termination */
hlt