Hello,

I recently purchased an USB adapter to read SD cards. On my first try, i made a mistake and put the SD card on the wrong side. This instantantly crashed my FreeBSD system. Here is the KDB output : 


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..
Unread portion of the kernel message buffer:
panic: kmem_malloc(1848643584): kmem_map too small: 43110400 total allocated
cpuid = 0
Uptime: 7h51m49s
Physical memory: 1002 MB
Dumping 183 MB: 168 152 136 120 104 88 72 56 40 24 8
..
Loaded symbols for /boot/kernel/drm.ko
#0  doadump () at pcpu.h:196
196		__asm __volatile("movl %%fs:0,%0" : "=r" (td));
(kgdb) list
191	static __inline struct thread *
192	__curthread(void)
193	{
194		struct thread *td;
195	
196		__asm __volatile("movl %%fs:0,%0" : "=r" (td));
197		return (td);
198	}
199	#define	curthread		(__curthread())
200	
(kgdb) backtrace
#0  doadump () at pcpu.h:196
#1  0xc0754a8f in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:418
#2  0xc0754d54 in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:574
#3  0xc0965432 in kmem_malloc (map=0xc147108c, size=1848643584, flags=2) at /usr/src/sys/vm/vm_kern.c:312
#4  0xc095c29a in page_alloc (zone=0x0, bytes=1848643584, pflag=0xe4276b4f "\002", wait=2) at /usr/src/sys/vm/uma_core.c:959
#5  0xc095ec0b in uma_large_malloc (size=1848643584, wait=2) at /usr/src/sys/vm/uma_core.c:2713
#6  0xc0745aa4 in malloc (size=1848643584, mtp=0xc0b324a0, flags=2) at /usr/src/sys/kern/kern_malloc.c:393
#7  0xc0700b2c in g_read_data (cp=0xc6644c80, offset=Unhandled dwarf expression opcode 0x93
) at geom.h:300
#8  0xc06fb6a8 in g_bsd_try (gp=Variable "gp" is not available.
) at /usr/src/sys/geom/geom_bsd.c:211
#9  0xc06fbbf7 in g_bsd_taste (mp=0xc0b321e0, pp=0xc5a23580, flags=0) at /usr/src/sys/geom/geom_bsd.c:549
#10 0xc0703401 in g_new_provider_event (arg=0xc5a23580, flag=0) at /usr/src/sys/geom/geom_subr.c:543
#11 0xc07000bf in g_run_events () at /usr/src/sys/geom/geom_event.c:211
#12 0xc0701317 in g_event_procbody () at /usr/src/sys/geom/geom_kern.c:141
#13 0xc0732d11 in fork_exit (callout=0xc07012ac <g_event_procbody>, arg=0x0, frame=0xe4276d38) at /usr/src/sys/kern/kern_fork.c:804
#14 0xc09d31d0 in fork_trampoline () at /usr/src/sys/i386/i386/exception.s:264


Of course, this crash should never happen as i'm supposed to put the SD card on the right side :-) But i prefer to send this PR in case this could be avoided.

By the way, when the SD card is put on the right side, it works perfectly well.

Regards,
Stéphane Legrand.

Fix: 

Put the SD card on the right side! :-)
How-To-Repeat: Plug the USB card reader with a SD card put on the wrong side.