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92 lines
3.2 KiB
C
92 lines
3.2 KiB
C
/******************************** -*- C -*- ****************************
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*
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* Platform-independent layer inline functions (i386)
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*
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***********************************************************************/
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/***********************************************************************
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*
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* Copyright 2000, 2001, 2002, 2006 Free Software Foundation, Inc.
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* Written by Paolo Bonzini.
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*
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* This file is part of GNU lightning.
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*
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* GNU lightning is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published
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* by the Free Software Foundation; either version 3, or (at your option)
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* any later version.
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*
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* GNU lightning is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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* License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with GNU lightning; see the file COPYING.LESSER; if not, write to the
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* Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
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* MA 02110-1301, USA.
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*
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***********************************************************************/
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#ifndef __lightning_funcs_h
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#define __lightning_funcs_h
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#ifdef __linux__
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#include <unistd.h>
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#include <sys/mman.h>
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#endif
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static void
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jit_flush_code(void *dest, void *end)
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{
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/* On the x86, the PROT_EXEC bits are not handled by the MMU.
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However, the kernel can emulate this by setting the code
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segment's limit to the end address of the highest page
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whose PROT_EXEC bit is set.
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Linux kernels that do so and that disable by default the
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execution of the data and stack segment are becoming more
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and more common (Fedora, for example), so we implement our
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jit_flush_code as an mprotect. */
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#ifdef __linux__
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static unsigned long prev_page = 0, prev_length = 0;
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long page, length;
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#ifdef PAGESIZE
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const int page_size = PAGESIZE;
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#else
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static int page_size = -1;
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if (page_size == -1)
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page_size = sysconf (_SC_PAGESIZE);
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#endif
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page = (long) dest & ~(page_size - 1);
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length = ((char *) end - (char *) page + page_size - 1) & ~(page_size - 1);
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/* Simple-minded attempt at optimizing the common case where a single
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chunk of memory is used to compile multiple functions. */
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if (page >= prev_page && page + length <= prev_page + prev_length)
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return;
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mprotect ((void *) page, length, PROT_READ | PROT_WRITE | PROT_EXEC);
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/* See if we can extend the previously mprotect'ed memory area towards
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higher addresses: the starting address remains the same as before. */
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if (page >= prev_page && page <= prev_page + prev_length)
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prev_length = page + length - prev_page;
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/* See if we can extend the previously mprotect'ed memory area towards
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lower addresses: the highest address remains the same as before. */
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else if (page < prev_page && page + length >= prev_page
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&& page + length <= prev_page + prev_length)
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prev_length += prev_page - page, prev_page = page;
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/* Nothing to do, replace the area. */
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else
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prev_page = page, prev_length = length;
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#endif
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}
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#endif /* __lightning_funcs_h */
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