78 lines
1.9 KiB
C
78 lines
1.9 KiB
C
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/*
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* Copyright (c) 2018 William Pitcock <nenolod@dereferenced.org>
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* This software is provided 'as is' and without any warranty, express or
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* implied. In no event shall the authors be liable for any damages arising
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* from the use of this software.
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*/
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#define _GNU_SOURCE
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#include <stddef.h>
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#include <stdarg.h>
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#include <signal.h>
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#include <string.h>
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#include <stdint.h>
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extern void __start_context(void);
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void
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__makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
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{
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greg_t *sp;
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va_list va;
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int i;
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unsigned int uc_link;
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uc_link = (argc > 6 ? argc - 6 : 0) + 1;
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sp = (greg_t *) ((uintptr_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
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sp -= uc_link;
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sp = (greg_t *) (((uintptr_t) sp & -16L) - 8);
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ucp->uc_mcontext.gregs[REG_RIP] = (uintptr_t) func;
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ucp->uc_mcontext.gregs[REG_RBX] = (uintptr_t) &sp[uc_link];
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ucp->uc_mcontext.gregs[REG_RSP] = (uintptr_t) sp;
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sp[0] = (uintptr_t) &__start_context;
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sp[uc_link] = (uintptr_t) ucp->uc_link;
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va_start(va, argc);
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for (i = 0; i < argc; i++)
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switch (i)
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{
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case 0:
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ucp->uc_mcontext.gregs[REG_RDI] = va_arg (va, greg_t);
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break;
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case 1:
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ucp->uc_mcontext.gregs[REG_RSI] = va_arg (va, greg_t);
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break;
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case 2:
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ucp->uc_mcontext.gregs[REG_RDX] = va_arg (va, greg_t);
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break;
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case 3:
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ucp->uc_mcontext.gregs[REG_RCX] = va_arg (va, greg_t);
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break;
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case 4:
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ucp->uc_mcontext.gregs[REG_R8] = va_arg (va, greg_t);
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break;
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case 5:
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ucp->uc_mcontext.gregs[REG_R9] = va_arg (va, greg_t);
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break;
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default:
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sp[i - 5] = va_arg (va, greg_t);
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break;
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}
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va_end(va);
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}
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extern __typeof(__makecontext) makecontext __attribute__((weak, __alias__("__makecontext")));
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