62 lines
1.9 KiB
C
62 lines
1.9 KiB
C
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/*
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* Copyright (c) 2022 Ariadne Conill <ariadne@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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#include <stddef.h>
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#include <stdarg.h>
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#include <string.h>
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#include <stdint.h>
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#include <stdio.h>
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#include "defs.h"
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#include <libucontext/libucontext.h>
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extern void libucontext_trampoline(void);
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void
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libucontext_makecontext(libucontext_ucontext_t *ucp, void (*func)(void), int argc, ...)
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{
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libucontext_greg_t *sp;
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va_list va;
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int i;
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/* set up and align the stack. */
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sp = (libucontext_greg_t *) ((uintptr_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
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sp -= argc < 6 ? 0 : (argc - 6);
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sp = (libucontext_greg_t *) (((uintptr_t) sp & ~0x3));
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/* set up the ucontext structure */
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ucp->uc_mcontext.regs.gpr[REG_SP] = (libucontext_greg_t) sp;
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ucp->uc_mcontext.regs.gpr[REG_RA] = (libucontext_greg_t) &libucontext_trampoline;
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ucp->uc_mcontext.regs.gpr[REG_FP] = 0;
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ucp->uc_mcontext.regs.gpr[REG_SA] = (libucontext_greg_t) func;
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ucp->uc_mcontext.regs.gpr[REG_LR] = (libucontext_greg_t) ucp->uc_link;
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va_start(va, argc);
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/* args less than argv[6] have dedicated registers, else they overflow onto stack */
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for (i = 0; i < argc; i++)
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{
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if (i < 6)
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ucp->uc_mcontext.regs.gpr[i + 3] = va_arg (va, libucontext_greg_t);
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else
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sp[i - 6] = va_arg (va, libucontext_greg_t);
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}
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va_end(va);
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}
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#ifdef EXPORT_UNPREFIXED
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extern __typeof(libucontext_makecontext) makecontext __attribute__((weak, __alias__("libucontext_makecontext")));
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extern __typeof(libucontext_makecontext) __makecontext __attribute__((weak, __alias__("libucontext_makecontext")));
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#endif
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