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REDZONE(9)		 BSD Kernel Developer's	Manual		    REDZONE(9)

NAME
     RedZone --	buffer corruptions detector

SYNOPSIS
     options DEBUG_REDZONE

DESCRIPTION
     RedZone detects buffer underflow and buffer overflow bugs at runtime.
     Currently RedZone only detects buffer corruptions for memory allocated
     with malloc(9).  When such	corruption is detected two backtraces are
     printed on	the console.  The first	one shows from where memory was	allo-
     cated, the	second one shows from where memory was freed.  By default the
     system will not panic when	buffer corruption is detected.	This can be
     changed by	setting	the vm.redzone.panic sysctl(8) variable	to 1.  The
     amount of extra memory allocated for RedZone's needs is stored in the
     vm.redzone.extra_mem sysctl(8) variable.

EXAMPLE
     The example below shows the logs from the detection of a buffer underflow
     and a buffer overflow.

	   REDZONE: Buffer underflow detected. 2 bytes corrupted before	0xc8688580 (16 bytes allocated).
	   Allocation backtrace:
	   #0 0xc0583e4e at redzone_setup+0x3c
	   #1 0xc04a23fa at malloc+0x19e
	   #2 0xcdeb69ca at redzone_modevent+0x60
	   #3 0xc04a3f3c at module_register_init+0x82
	   #4 0xc049d96a at linker_file_sysinit+0x8e
	   #5 0xc049dc7c at linker_load_file+0xed
	   #6 0xc04a041f at linker_load_module+0xc4
	   #7 0xc049e883 at kldload+0x116
	   #8 0xc05d9b3d at syscall+0x325
	   #9 0xc05c944f at Xint0x80_syscall+0x1f
	   Free	backtrace:
	   #0 0xc0583f92 at redzone_check+0xd4
	   #1 0xc04a2422 at free+0x1c
	   #2 0xcdeb69a6 at redzone_modevent+0x3c
	   #3 0xc04a438d at module_unload+0x61
	   #4 0xc049e0b3 at linker_file_unload+0x89
	   #5 0xc049e979 at kern_kldunload+0x96
	   #6 0xc049ea00 at kldunloadf+0x2c
	   #7 0xc05d9b3d at syscall+0x325
	   #8 0xc05c944f at Xint0x80_syscall+0x1f

	   REDZONE: Buffer overflow detected. 4	bytes corrupted	after 0xc8688590 (16 bytes allocated).
	   Allocation backtrace:
	   #0 0xc0583e4e at redzone_setup+0x3c
	   #1 0xc04a23fa at malloc+0x19e
	   #2 0xcdeb69ca at redzone_modevent+0x60
	   #3 0xc04a3f3c at module_register_init+0x82
	   #4 0xc049d96a at linker_file_sysinit+0x8e
	   #5 0xc049dc7c at linker_load_file+0xed
	   #6 0xc04a041f at linker_load_module+0xc4
	   #7 0xc049e883 at kldload+0x116
	   #8 0xc05d9b3d at syscall+0x325
	   #9 0xc05c944f at Xint0x80_syscall+0x1f
	   Free	backtrace:
	   #0 0xc0584020 at redzone_check+0x162
	   #1 0xc04a2422 at free+0x1c
	   #2 0xcdeb69a6 at redzone_modevent+0x3c
	   #3 0xc04a438d at module_unload+0x61
	   #4 0xc049e0b3 at linker_file_unload+0x89
	   #5 0xc049e979 at kern_kldunload+0x96
	   #6 0xc049ea00 at kldunloadf+0x2c
	   #7 0xc05d9b3d at syscall+0x325
	   #8 0xc05c944f at Xint0x80_syscall+0x1f

SEE ALSO
     sysctl(8),	malloc(9), memguard(9)

HISTORY
     RedZone first appeared in FreeBSD 7.0.

AUTHORS
     Pawel Jakub Dawidek <pjd@FreeBSD.org>

BUGS
     Currently,	RedZone	does not cooperate with	memguard(9).  Allocations from
     a memory type controlled by memguard(9) are simply	skipped, so buffer
     corruptions will not be detected there.

BSD			       January 31, 2006				   BSD
NAME | SYNOPSIS | DESCRIPTION | EXAMPLE | SEE ALSO | HISTORY | AUTHORS | BUGS

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