Finding Memory Leaks

The ::findleaks dcmd provides powerful and efficient detection of memory leaks in kernel crash dumps where the full set of kmem debug features has been enabled. The first execution of ::findleaks processes the dump for memory leaks (this can take a few minutes), and then coalesces the leaks by the allocation stack trace. The findleaks report shows a bufctl address and the topmost stack frame for each memory leak that was identified:

> ::findleaks
CACHE     LEAKED   BUFCTL CALLER
70039ba8       1 703746c0 pm_autoconfig+0x708
70039ba8       1 703748a0 pm_autoconfig+0x708
7003a028       1 70d3b1a0 sigaddq+0x108
7003c7a8       1 70515200 pm_ioctl+0x187c
------------------------------------------------------
   Total       4 buffers, 376 bytes

Using the bufctl pointers, you can obtain the complete stack backtrace of the allocation by applying the bufctl_audit macro:

> 70d3b1a0$<bufctl_audit
0x70d3b1a0:     next            addr            slab
                70a049c0        70d03b28        70bb7480
0x70d3b1ac:     cache           timestamp       thread
                7003a028        13f7cf63b3      70b38380
0x70d3b1bc:     lastlog         contents        stackdepth
                700d6e60        0               5
0x70d3b1c8:
                kmem_alloc+0x30
                sigaddq+0x108
                sigsendproc+0x210
                sigqkill+0x90
                kill+0x28

The programmer can usually use the bufctl_audit information and the allocation stack trace to quickly track down the code path that leaks the given buffer.