root@wl ~ # mdb -k Loading modules: [ ... ] > ::memstat Page Summary Pages MB %Tot ------------ ---------------- ---------------- ---- Kernel 126404 493 13% ZFS File Data 330911 1292 34% Anon 90669 354 9% Exec and libs 10144 39 1% Page cache 7231 28 1% Free (cachelist) 34572 135 4% Free (freelist) 380315 1485 39% Total 980246 3829 root@wl ~ #
#include <unistd.h>
#include <stdlib.h>
void main () {
void * m;
m = malloc(10);
m = malloc(30); // 위에서 할당한 10바이트의 메모리를 해제할 수 없다.
m = malloc(50); // 위에서 할당한 30바이트의 메모리를 해제할 수 없다.
sleep(30);
}
root@wl # cc -g -o leak leak.c 1) root@wl # UMEM_DEBUG=default UMEM_LOGGING=transaction LD_PRELOAD=libumem.so.1 ./leak & 2) [1] 2171 root@wl # gcore 2171 3) gcore: core.2171 dumped root@wl # mdb core.2171 4) Loading modules: [ libumem.so.1 libc.so.1 ld.so.1 ] > ::umem_status > ::umem_log > ::umalog ... > ::findleaks CACHE LEAKED BUFCTL CALLER 080798d0 1 0808ae30 main+0xf 08079c50 1 0808eaf8 main+0x1e ---------------------------------------------------------------------- Total 2 buffers, 64 bytes Ctrl+D root@wl #1) 샘플 프로그램을 만들고 컴파일한다.
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
void main () {
printf("PID: %d\n", getpid());
void * m = malloc(10 * 1024);
printf("%s\n", "10킬로바이트할당");
long a = (long) m / 4;
long b = (long) m % 4;
while (1==1) {
m = malloc(200 * 1024);
printf("%s\n", "200킬로바이트할당");
sleep(20); // STEP 1
void * m2 = (void *) (a * 4 + b);
free(m2);
printf("%s\n", "10킬로바이트해제");
sleep(20); // STEP 2
free(m);
printf("%s\n", "200킬로바이트해제");
sleep(20); // STEP 3
break;
}
}
root@wl # UMEM_DEBUG=default UMEM_LOGGING=transaction LD_PRELOAD=libumem.so.1 ./leak2 PID: 2631 10킬로바이트할당 200킬로바이트할당 10킬로바이트해제 200킬로바이트해제 root@wl #
root@wl # mdb core.2631.step1 STEP 1 Loading modules: [ libumem.so.1 libc.so.1 ld.so.1 ] > ::findleaks CACHE LEAKED BUFCTL CALLER 08082a90 1 0808af08 main+0x25 ---------------------------------------------------------------------- Total 1 buffer, 12288 bytes > root@wl # mdb core.2631.step2 STEP 2 Loading modules: [ libumem.so.1 libc.so.1 ld.so.1 ] > ::findleaks CACHE LEAKED BUFCTL CALLER ---------------------------------------------------------------------- Total 0 buffers, 0 bytes > root@wl # mdb core.2631.step3 STEP 3 Loading modules: [ libumem.so.1 libc.so.1 ld.so.1 ] > ::findleaks CACHE LEAKED BUFCTL CALLER ---------------------------------------------------------------------- Total 0 buffers, 0 bytes > root@wl #
#include <unistd.h>
#include <stdlib.h>
void main () {
void * m;
m = malloc(10);
m = malloc(50);
free(m);
}
#!/usr/sbin/dtrace -s
pid$target:$1:malloc:entry
{
ustack();
}
pid$target:$1:malloc:return
{
printf("%s: %x\n", probefunc, arg1);
}
pid$target:$1:free:entry
{
printf("%s: %x\n", probefunc, arg0);
}
root@wl ~ # cc -o leak3 leak3.c
root@wl ~ # dtrace -s mfs.d -c ./leak3 libc
dtrace: script 'mfs.d' matched 3 probes
dtrace: pid 7205 has exited
CPU ID FUNCTION:NAME
0 57771 malloc:entry
libc.so.1`malloc
leak3`main+0xf
leak3`_start+0x7d
0 57772 malloc:return malloc: 80608a8 1)
0 57771 malloc:entry
libc.so.1`malloc
leak3`main+0x1e
leak3`_start+0x7d
0 57772 malloc:return malloc: 8060ea8 2)
0 57773 free:entry free: 8060ea8 3)
1) 80608a8 주소에 메모리 할당
root@wl ~ # cc -o leak3 -g leak3.c
root@wl ~ # dbx leak3
For information about new features see `help changes'
To remove this message, put `dbxenv suppress_startup_message 7.7' in your .dbxrc
Reading leak3
Reading ld.so.1
Reading libc.so.1
(dbx) help check
...
(dbx) check -leaks
leaks checking - ON
(dbx) run
Running: leak3
(process id 7796)
Reading rtcapihook.so
Reading libdl.so.1
Reading rtcaudit.so
Reading libmapmalloc.so.1
Reading libgen.so.1
Reading libm.so.2
Reading rtcboot.so
Reading librtc.so
RTC: Enabling Error Checking...
RTC: Running program...
Checking for memory leaks...
Actual leaks report (actual leaks: 1 total size: 10 bytes)
Total Num of Leaked Allocation call stack
Size Blocks Block
Address
========== ====== =========== =======================================
10 1 0x80608b0 main
Possible leaks report (possible leaks: 0 total size: 0 bytes)
execution completed, exit code is 0
(dbx) exit
root@wl ~ #
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