2020-06-15 14:18:57 +00:00
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/assert.h"
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#include "libc/bits/bits.h"
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2020-07-01 02:55:47 +00:00
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#include "libc/bits/popcnt.h"
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2020-06-15 14:18:57 +00:00
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#include "libc/bits/safemacros.h"
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#include "libc/calls/calls.h"
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#include "libc/runtime/buffer.h"
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#include "libc/runtime/mappings.h"
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#include "libc/runtime/runtime.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/prot.h"
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#define kGuard PAGESIZE
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#define kGrain FRAMESIZE
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/**
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* Allocates page-guarded buffer.
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*
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* ┌─────────────────────────────────────┬s─i─g─s─e─g─v┐
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* │ 𝑣₀..𝑣ₙ₋₁ │𝑣ₙ..𝑣ₙ₊₄₀₉₆₋₁│
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* └─────────────────────────────────────┴s─i─g─s─e─g─v┘
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*
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* @param b is metadata object owned by caller, initialized to zero for
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* first call; subsequent calls will resize
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* @param a is alignment requirement in bytes, e.g. 1,2,4,8,16,...
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* @param n is buffer size in bytes
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* @return b->p
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* @see ralloc()
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*/
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void *balloc(struct GuardedBuffer *b, unsigned a, size_t n) {
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int rc;
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char *p;
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size_t mi, need;
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struct AddrSize az;
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struct MemoryCoord mc;
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assert(a >= 1);
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assert(a <= kGuard);
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assert(kGuard < kGrain);
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2020-07-01 02:55:47 +00:00
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assert(popcnt(a) == 1);
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assert(popcnt(kGuard) == 1);
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assert(popcnt(kGrain) == 1);
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2020-06-15 14:18:57 +00:00
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assert(n < 0x800000000000ul - kGrain - kGuard);
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if (n) {
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az.addr = 0;
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az.size = 0;
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n = roundup(n, a);
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need = roundup(n + kGuard, kGrain);
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if (b->p) {
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mc = ADDRSIZE_TO_COORD(b->p, 1);
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mi = findmapping(mc.y);
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if (mi && ISOVERLAPPING(mc, _mm.p[mi - 1])) {
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az = COORD_TO_ADDRSIZE(_mm.p[mi - 1]);
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if (az.size < need) {
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rc = munmap(az.addr, az.size);
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assert(rc != -1);
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az.addr = NULL;
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az.size = 0;
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}
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}
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}
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if (!az.size) {
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if ((p = mapanon(need)) == MAP_FAILED) abort();
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if (mprotect(p + need - kGuard, kGuard, PROT_NONE) == -1) abort();
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} else {
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p = az.addr;
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}
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b->p = p + need - kGuard - n;
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}
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return b->p;
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}
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