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riscv64: add makecontext() and __start_context() trampoline

pull/21/head
Ariadne Conill 2020-05-18 03:19:22 +00:00
parent e9308ef58f
commit e11fa34822
2 changed files with 91 additions and 0 deletions
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62
arch/riscv64/makecontext.c Normal file
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/*
* Copyright (c) 2018 Ariadne Conill <ariadne@dereferenced.org>
*
* 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.
*/
#define _GNU_SOURCE
#include <stddef.h>
#include <stdarg.h>
#include <signal.h>
#include <string.h>
#include <stdint.h>
#include <stdio.h>
#include "defs.h"
extern void __start_context(void);
void
__makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
{
greg_t *sp, *regp;
va_list va;
int i;
/* set up and align the stack. */
sp = (greg_t *) ((uintptr_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
sp -= argc < 8 ? 0 : argc - 8;
sp = (greg_t *) (((uintptr_t) sp & -16L));
/* set up the ucontext structure */
ucp->uc_mcontext.gregs[REG_PC] = (greg_t) __start_context;
ucp->uc_mcontext.gregs[REG_S0] = 0;
ucp->uc_mcontext.gregs[REG_S1] = (greg_t) func;
ucp->uc_mcontext.gregs[REG_S2] = (greg_t) ucp->uc_link;
ucp->uc_mcontext.gregs[REG_SP] = (greg_t) sp;
ucp->uc_mcontext.gregs[REG_PC_SAVE] = 0;
va_start(va, argc);
/* first 8 args go in $a0 through $a7. */
regp = &(ucp->uc_mcontext.gregs[REG_A0]);
for (i = 0; (i < argc && i < 8); i++)
*regp++ = va_arg (va, greg_t);
/* remainder overflows into stack */
for (; i < argc; i++)
*sp++ = va_arg (va, greg_t);
va_end(va);
}
extern __typeof(__makecontext) makecontext __attribute__((weak, __alias__("__makecontext")));

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arch/riscv64/startcontext.S Normal file
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/*
* Copyright (c) 2020 Ariadne Conill <ariadne@dereferenced.org>
*
* 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.
*/
#include "defs.h"
FUNC(__start_context)
/* call the function passed to makecontext() */
jalr s1
/* check for linked context */
beqz s2, no_linked_context
/* if one is set, invoke it */
mv a0, s2
jal __setcontext
/* otherwise, exit. */
no_linked_context:
j exit
END(__start_context)