[U-Boot] [PATCH v2 1/2] Introduce generic TPM support in u-boot

[Vadim Bendebury]

On Sat, Oct 15, 2011 at 8:31 PM, Marek Vasut <marek.vasut at gmail.com> wrote:
> On Sunday, October 16, 2011 03:04:33 AM Vadim Bendebury wrote:
>> On Sat, Oct 15, 2011 at 2:09 PM, Marek Vasut <marek.vasut at gmail.com> wrote:
>> > On Saturday, October 15, 2011 08:47:39 PM Vadim Bendebury wrote:
>> >> Dear Marek Vasut,
>> >>
>> >> thank you for your comments, please see below:
>> >>
>> >> On Sat, Oct 15, 2011 at 11:08 AM, Marek Vasut <marek.vasut at gmail.com>
> wrote:
>> >> > On Saturday, October 15, 2011 05:38:50 AM Vadim Bendebury wrote:
>> >> >> TPM (Trusted Platform Module) is an integrated circuit and
>> >> >> software platform that provides computer manufacturers with the
>> >> >> core components of a subsystem used to assure authenticity,
>> >> >> integrity and confidentiality.
>> >> >
>> >> > [...]
>> >> >
>> >> > Quick points:
>> >> > * The license
>> >>
>> >> Please suggest the appropriate file header text.
>> >
>> > Uh ... you should know the license !!!
>>
>> removed the BSD part
>
> Are you sure you're not relicensing code you don't own ? I'm just curious,
> what's the origin of the code ? I'd prefer to avoid legal crap.
>

I am sure.

>> [..]
>>
>> >> >> +
>> >> >> +struct lpc_tpm {
>> >> >> +     struct tpm_locality locality[TPM_TOTAL_LOCALITIES];
>> >> >> +};
>> >> >
>> >> > Do you need such envelope ?
>> >>
>> >> I think I do - this accurately describes the structure of the chip.
>> >
>> > There's just one member ... it's weird?
>>
>> I think it is appropriate in this case to encapsulate the entire chip
>> description in a structure. Among other things makes it easier to pass
>> a pointer to the chip description around.
>
> can't you pass the locality array ?
>

no, because it would not be clear how big the array is.

>>
>> [..]
>>
>> >> > Dot missing at the end.
>> >>
>> >> ok.
>> >
>> > Please fix globally.
>>
>> done
>>
>> >> >> +#define TPM_DRIVER_ERR               (-1)
>> >> >> +
>> >> >> + /* 1 second is plenty for anything TPM does.*/
>> >> >> +#define MAX_DELAY_US (1000 * 1000)
>> >> >> +
>> >> >> +/* Retrieve burst count value out of the status register contents.
>> >> >> */ +#define BURST_COUNT(status) ((u16)(((status) >>
>> >> >> TIS_STS_BURST_COUNT_SHIFT) & \ +
>> >> >>  TIS_STS_BURST_COUNT_MASK))
>> >> >
>> >> > Do you need the cast ?
>> >>
>> >> I think it demonstrates the intentional truncation of the value, it
>> >> gets assigned to u16 values down the road, prevents compiler warnings
>> >> about assigning incompatible values in some cases.
>> >
>> > Make it an inline function then, this will do the typechecking for you.
>>
>> I am not sure what is wrong with a short macro in this case - is this
>> against the coding style?
>
> It doesn't do typechecking.

but the code around it does, doesn't it?

Sorry, as I said, I am new here: how does this work on this project -
does the submitter have to agree to all reviewer's comments? Can I ask
somebody else to confirm that using a macro in this case in
inappropriate?

>>
>> >> >> +
>> >> >> +/*
>> >> >> + * Structures defined below allow creating descriptions of TPM
>> >> >> vendor/device + * ID information for run time discovery. The only
>> >> >> device the system knows + * about at this time is Infineon slb9635
>> >> >> + */
>> >> >> +struct device_name {
>> >> >> +     u16 dev_id;
>> >> >> +     const char * const dev_name;
>> >> >> +};
>> >> >> +
>> >> >> +struct vendor_name {
>> >> >> +     u16 vendor_id;
>> >> >> +     const char *vendor_name;
>> >> >> +     const struct device_name *dev_names;
>> >> >> +};
>> >> >> +
>> >> >> +static const struct device_name infineon_devices[] = {
>> >> >> +     {0xb, "SLB9635 TT 1.2"},
>> >> >> +     {0}
>> >> >> +};
>> >> >> +
>> >> >> +static const struct vendor_name vendor_names[] = {
>> >> >> +     {0x15d1, "Infineon", infineon_devices},
>> >> >> +};
>> >> >> +
>> >> >> +/*
>> >> >> + * Cached vendor/device ID pair to indicate that the device has been
>> >> >> already + * discovered
>> >> >> + */
>> >> >> +static u32 vendor_dev_id;
>> >> >> +
>> >> >> +/* TPM access going through macros to make tracing easier. */
>> >> >> +#define tpm_read(ptr) ({ \
>> >> >> +     u32  __ret; \
>> >> >> +     __ret = (sizeof(*ptr) == 1) ? readb(ptr) : readl(ptr); \
>> >> >> +      debug(PREFIX "Read reg 0x%x returns 0x%x\n", \
>> >> >> +            (u32)ptr - (u32)lpc_tpm_dev, __ret); \
>> >> >> +                                      __ret; })
>> >> >> +
>> >> >
>> >> > Make this inline function
>> >> >
>> >> >> +#define tpm_write(value, ptr) ({                \
>> >> >> +     u32 __v = value;        \
>> >> >> +     debug(PREFIX "Write reg 0x%x with 0x%x\n", \
>> >> >> +            (u32)ptr - (u32)lpc_tpm_dev, __v); \
>> >> >> +     if (sizeof(*ptr) == 1) \
>> >> >> +             writeb(__v, ptr); \
>> >> >> +     else \
>> >> >> +             writel(__v, ptr); })
>> >> >> +
>> >> >
>> >> > DTTO
>> >>
>> >> Are you sure these will work as inline functions?
>> >
>> > Why not ? Also, why do you introduce the __v ?
>>
>> macro vs function: need to be able to tell the pointed object size at run
>> time.
>
> This seems wrong like hell.

You are entitled to your opinion, but you should not be suggesting to
change this code to inline functions, because it would break it.

>>
>> __v is needed to avoid side effects when invoking the macro.
>
> Side effects ? What side effects ?
>

https://www.securecoding.cert.org/confluence/display/seccode/PRE31-C.+Avoid+side-effects+in+arguments+to+unsafe+macros

> [...]
>
> Cheers
> _______________________________________________
> U-Boot mailing list
> U-Boot at lists.denx.de
> http://lists.denx.de/mailman/listinfo/u-boot
>

cheers,
/vb