Re: [PATCH v4 04/10] taint: Add TAINT_FWCTL

[Dave Jiang <dave.jiang@intel.com>]

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@nvidia.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> ---
>  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"