Date: Sun, 19 Dec 1999 23:37:13 +0100 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: Garrett Wollman <wollman@khavrinen.lcs.mit.edu> Cc: freebsd-bugs@FreeBSD.ORG Subject: Re: kern/15554: malloc fails in OMAGIC programs Message-ID: <7706.945643033@critter.freebsd.dk> In-Reply-To: Your message of "Sun, 19 Dec 1999 15:22:04 EST." <199912192022.PAA65483@khavrinen.lcs.mit.edu>
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In message <199912192022.PAA65483@khavrinen.lcs.mit.edu>, Garrett Wollman write
s:
><<On Sun, 19 Dec 1999 04:50:02 -0800 (PST), Poul-Henning Kamp <phk@critter.freebsd.dk> said:
>
>> I thought programs started out at 0x0 or at least close to zero ?
>
>Not ELF programs.
I know, but I thought we tried to keep the start low still.
Anyway, the problem is obviously sbrk(2)/brk(2) failing:
syv# cat a.c
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
int
main (int argc, char **argv)
{
char *p = malloc (8192);
char buf[4096];
int fd, i;
fd = open("/proc/curproc/map", O_RDONLY);
if (fd >= 0) {
do {
i = read(fd, buf, sizeof buf);
if (i > 0)
write(1, buf, i);
} while (i > 0);
close(fd);
}
if (!p) {
char badmalloc[] = "malloc failed\n";
write (2, badmalloc, sizeof (badmalloc));
write (2, strerror (errno), strlen (strerror (errno)));
write (2, "\n", 1);
exit (1);
}
exit (0);
}
syv# cc -static -N -o a a.c
syv# ktrace ./a
0x8048000 0x804a000 2 0 0xcdc0f180 rwx 1 0 0x0 COW NC vnode
0x804a000 0x804b000 1 0 0xc0279fe0 rwx 1 0 0x2180 NCOW NNC default
0x20000000 0x20001000 1 0 0xcdc324e0 rwx 1 0 0x2180 NCOW NNC default
0xbfbe0000 0xbfc00000 2 0 0xcdc60de0 rwx 1 0 0x2180 NCOW NNC default
malloc failed
Cannot allocate memory
syv# kdump
3101 ktrace RET ktrace 0
3101 ktrace CALL execve(0xbfbffd6f,0xbfbffcb0,0xbfbffcb8)
3101 ktrace NAMI "./a"
3101 a RET execve 0
3101 a CALL readlink(0x804a7d4,0xbfbfeba4,0x3f)
3101 a NAMI "/etc/malloc.conf"
3101 a RET readlink -1 errno 2 No such file or directory
3101 a CALL mmap(0,0x1000,0x3,0x1002,0xffffffff,0,0,0)
3101 a RET mmap 536870912/0x20000000
3101 a CALL break(0x804c000)
3101 a RET break -1 errno 12 Cannot allocate memory
3101 a CALL break(0x804d000)
3101 a RET break -1 errno 12 Cannot allocate memory
3101 a CALL open(0x8049d01,0,0)
3101 a NAMI "/proc/curproc/map"
3101 a RET open 3
3101 a CALL read(0x3,0xbfbfec60,0x1000)
3101 a GIO fd 3 read 265 bytes
"0x8048000 0x804a000 2 0 0xcdc0f180 rwx 1 0 0x0 COW NC vnode
0x804a000 0x804b000 1 0 0xc0279fe0 rwx 1 0 0x2180 NCOW NNC default
0x20000000 0x20001000 1 0 0xcdc324e0 rwx 1 0 0x2180 NCOW NNC default
0xbfbe0000 0xbfc00000 2 0 0xcdc60de0 rwx 1 0 0x2180 NCOW NNC default
"
3101 a RET read 265/0x109
3101 a CALL write(0x1,0xbfbfec60,0x109)
3101 a GIO fd 1 wrote 265 bytes
"0x8048000 0x804a000 2 0 0xcdc0f180 rwx 1 0 0x0 COW NC vnode
0x804a000 0x804b000 1 0 0xc0279fe0 rwx 1 0 0x2180 NCOW NNC default
0x20000000 0x20001000 1 0 0xcdc324e0 rwx 1 0 0x2180 NCOW NNC default
0xbfbe0000 0xbfc00000 2 0 0xcdc60de0 rwx 1 0 0x2180 NCOW NNC default
"
3101 a RET write 265/0x109
3101 a CALL read(0x3,0xbfbfec60,0x1000)
3101 a GIO fd 3 read 0 bytes
""
3101 a RET read 0
3101 a CALL close(0x3)
3101 a RET close 0
3101 a CALL write(0x2,0xbfbfec48,0xf)
3101 a GIO fd 2 wrote 15 bytes
"malloc failed
\0"
3101 a RET write 15/0xf
3101 a CALL write(0x2,0x804a680,0x16)
3101 a GIO fd 2 wrote 22 bytes
"Cannot allocate memory"
3101 a RET write 22/0x16
3101 a CALL write(0x2,0x8049d22,0x1)
3101 a GIO fd 2 wrote 1 byte
"
"
3101 a RET write 1
3101 a CALL exit(0x1)
--
Poul-Henning Kamp FreeBSD coreteam member
phk@FreeBSD.ORG "Real hackers run -current on their laptop."
FreeBSD -- It will take a long time before progress goes too far!
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