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libc: rewrite brk() and sbrk() 

Also fix Coverity 1 scan defects, CID 155773 and CID 155768, removing
less-than-zero comparisons of unsigned values that were never true.
This commit is contained in:
Giacomo Tesio 2017-01-18 21:35:11 +01:00
parent 6e816b293d
commit b05c21397e
1 changed files with 36 additions and 32 deletions
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68
sys/src/lib/c/9sys/sbrk.c
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@ -1,56 +1,60 @@
/*
* This file is part of the UCB release of Plan 9. It is subject to the license
* terms in the LICENSE file found in the top-level directory of this
* distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
* part of the UCB release of Plan 9, including this file, may be copied,
* modified, propagated, or distributed except according to the terms contained
* in the LICENSE file.
* This file is part of Jehanne.
*
* Copyright (C) 2017 Giacomo Tesio <giacomo@tesio.it>
*
* Jehanne is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, version 2 of the License.
*
* Jehanne is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Jehanne. If not, see <http://www.gnu.org/licenses/>.
*/
#define PORTABLE_SYSCALLS
#include <u.h>
#include <libc.h>
extern char end[];
static char *bloc = { end };
static char *last_brk = { end };
enum
{
Round = 7
};
#define ROUND_BRK(b) (((uintptr_t)b + 7) & ~7)
uintptr_t
brk_(uintptr_t p)
static uintptr_t
setbrk(uintptr_t p)
{
long f;
f = create("#0/brk/set", -1, p);
if(f >= 0){
/* this should never happen */
close(f);
return -1;
}
return (uintptr_t)~f;
long b;
/* assert: devself is still working */
assert((b = create("#0/brk/set", -1, p)) < 0);
if(b == -1)
return ~0; // an error occurred
return (uintptr_t)~b;
}
int
brk(void *p)
{
uintptr_t bl;
uintptr_t new_brk;
bl = ((uintptr_t)p + Round) & ~Round;
if(brk_(bl) < 0)
new_brk = ROUND_BRK(p);
if(setbrk(new_brk) == ~0)
return -1;
bloc = (char*)bl;
last_brk = (char*)new_brk;
return 0;
}
void*
sbrk(uint32_t n)
sbrk(uint32_t increment)
{
uintptr_t bl;
uintptr_t new_brk;
bl = ((uintptr_t)bloc + Round) & ~Round;
if(brk_(bl+n) < 0)
new_brk = ROUND_BRK(last_brk);
if(setbrk(new_brk+increment) == ~0)
return (void*)-1;
bloc = (char*)bl + n;
return (void*)bl;
last_brk = (char*)new_brk + increment;
return (void*)new_brk;
}