On 2/6/25 5:13 PM, Jason Gunthorpe wrote:
> Requesting a fwctl scope of access that includes mutating device debug
> data will cause the kernel to be tainted. Changing the device operation
> through things in the debug scope may cause the device to malfunction in
> undefined ways. This should be reflected in the TAINT flags to help any
> debuggers understand that something has been done.
>
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> ---
> Documentation/admin-guide/tainted-kernels.rst | 5 +++++
> include/linux/panic.h | 3 ++-
> kernel/panic.c | 1 +
> tools/debugging/kernel-chktaint | 8 ++++++++
> 4 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst
> index 700aa72eecb169..a0cc017e44246f 100644
> --- a/Documentation/admin-guide/tainted-kernels.rst
> +++ b/Documentation/admin-guide/tainted-kernels.rst
> @@ -101,6 +101,7 @@ Bit Log Number Reason that got the kernel tainted
> 16 _/X 65536 auxiliary taint, defined for and used by distros
> 17 _/T 131072 kernel was built with the struct randomization plugin
> 18 _/N 262144 an in-kernel test has been run
> + 19 _/J 524288 userspace used a mutating debug operation in fwctl
> === === ====== ========================================================
>
> Note: The character ``_`` is representing a blank in this table to make reading
> @@ -184,3 +185,7 @@ More detailed explanation for tainting
> build time.
>
> 18) ``N`` if an in-kernel test, such as a KUnit test, has been run.
> +
> + 19) ``J`` if userpace opened /dev/fwctl/* and performed a FWTCL_RPC_DEBUG_WRITE
> + to use the devices debugging features. Device debugging features could
> + cause the device to malfunction in undefined ways.
> diff --git a/include/linux/panic.h b/include/linux/panic.h
> index 54d90b6c5f47bd..2494d51707ef42 100644
> --- a/include/linux/panic.h
> +++ b/include/linux/panic.h
> @@ -74,7 +74,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout)
> #define TAINT_AUX 16
> #define TAINT_RANDSTRUCT 17
> #define TAINT_TEST 18
> -#define TAINT_FLAGS_COUNT 19
> +#define TAINT_FWCTL 19
> +#define TAINT_FLAGS_COUNT 20
> #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1)
>
> struct taint_flag {
> diff --git a/kernel/panic.c b/kernel/panic.c
> index d8635d5cecb250..0c55eec9e8744a 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -511,6 +511,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
> TAINT_FLAG(AUX, 'X', ' ', true),
> TAINT_FLAG(RANDSTRUCT, 'T', ' ', true),
> TAINT_FLAG(TEST, 'N', ' ', true),
> + TAINT_FLAG(FWCTL, 'J', ' ', true),
> };
>
> #undef TAINT_FLAG
> diff --git a/tools/debugging/kernel-chktaint b/tools/debugging/kernel-chktaint
> index 279be06332be99..e7da0909d09707 100755
> --- a/tools/debugging/kernel-chktaint
> +++ b/tools/debugging/kernel-chktaint
> @@ -204,6 +204,14 @@ else
> echo " * an in-kernel test (such as a KUnit test) has been run (#18)"
> fi
>
> +T=`expr $T / 2`
> +if [ `expr $T % 2` -eq 0 ]; then
> + addout " "
> +else
> + addout "J"
> + echo " * fwctl's mutating debug interface was used (#19)"
> +fi
> +
> echo "For a more detailed explanation of the various taint flags see"
> echo " Documentation/admin-guide/tainted-kernels.rst in the Linux kernel sources"
> echo " or https://kernel.org/doc/html/latest/admin-guide/tainted-kernels.html";
