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+Tainted kernels
+---------------
+
+Some oops reports contain the string **'Tainted: '** after the program
+counter. This indicates that the kernel has been tainted by some
+mechanism. The string is followed by a series of position-sensitive
+characters, each representing a particular tainted value.
+
+ 1) ``G`` if all modules loaded have a GPL or compatible license, ``P`` if
+ any proprietary module has been loaded. Modules without a
+ MODULE_LICENSE or with a MODULE_LICENSE that is not recognised by
+ insmod as GPL compatible are assumed to be proprietary.
+
+ 2) ``F`` if any module was force loaded by ``insmod -f``, ``' '`` if all
+ modules were loaded normally.
+
+ 3) ``S`` if the oops occurred on an SMP kernel running on hardware that
+ hasn't been certified as safe to run multiprocessor.
+ Currently this occurs only on various Athlons that are not
+ SMP capable.
+
+ 4) ``R`` if a module was force unloaded by ``rmmod -f``, ``' '`` if all
+ modules were unloaded normally.
+
+ 5) ``M`` if any processor has reported a Machine Check Exception,
+ ``' '`` if no Machine Check Exceptions have occurred.
+
+ 6) ``B`` if a page-release function has found a bad page reference or
+ some unexpected page flags.
+
+ 7) ``U`` if a user or user application specifically requested that the
+ Tainted flag be set, ``' '`` otherwise.
+
+ 8) ``D`` if the kernel has died recently, i.e. there was an OOPS or BUG.
+
+ 9) ``A`` if the ACPI table has been overridden.
+
+ 10) ``W`` if a warning has previously been issued by the kernel.
+ (Though some warnings may set more specific taint flags.)
+
+ 11) ``C`` if a staging driver has been loaded.
+
+ 12) ``I`` if the kernel is working around a severe bug in the platform
+ firmware (BIOS or similar).
+
+ 13) ``O`` if an externally-built ("out-of-tree") module has been loaded.
+
+ 14) ``E`` if an unsigned module has been loaded in a kernel supporting
+ module signature.
+
+ 15) ``L`` if a soft lockup has previously occurred on the system.
+
+ 16) ``K`` if the kernel has been live patched.
+
+The primary reason for the **'Tainted: '** string is to tell kernel
+debuggers if this is a clean kernel or if anything unusual has
+occurred. Tainting is permanent: even if an offending module is
+unloaded, the tainted value remains to indicate that the kernel is not
+trustworthy.