Re: [PATCH 1/3] fdt: common API to populate kaslr seed

[Sean Edmond <seanedmond@linux.microsoft.com>]

On 2023-08-08 7:03 p.m., Simon Glass wrote:
> Hi,
>
> On Fri, 4 Aug 2023 at 17:34, <seanedmond@linux.microsoft.com> wrote:
>> From: Dhananjay Phadke <dphadke@linux.microsoft.com>
>>
>> fdt_fixup_kaslr_seed() will update given FDT with random seed value.
>> Source for random seed can be TPM or RNG driver in u-boot or sec
>> firmware (ARM).
>>
>> Signed-off-by: Dhananjay Phadke <dphadke@linux.microsoft.com>
>> ---
>>   arch/arm/cpu/armv8/sec_firmware.c | 32 +++++++------------------------
>>   common/fdt_support.c              | 31 ++++++++++++++++++++++++++++++
>>   include/fdt_support.h             |  3 +++
>>   3 files changed, 41 insertions(+), 25 deletions(-)
> We need to find a way to use the ofnode API here.
>
>> diff --git a/arch/arm/cpu/armv8/sec_firmware.c b/arch/arm/cpu/armv8/sec_firmware.c
>> index c0e8726346..84ba49924e 100644
>> --- a/arch/arm/cpu/armv8/sec_firmware.c
>> +++ b/arch/arm/cpu/armv8/sec_firmware.c
>> @@ -411,46 +411,28 @@ int sec_firmware_init(const void *sec_firmware_img,
>>   /*
>>    * fdt_fix_kaslr - Add kalsr-seed node in Device tree
>>    * @fdt:               Device tree
>> - * @eret:              0 in case of error, 1 for success
>> + * @eret:              0 for success
>>    */
>>   int fdt_fixup_kaslr(void *fdt)
> You could pass an oftree to this function, e.g. obtained with:
>
> oftree_from_fdt(fdt)

The common API I added is fdt_fixup_kaslr_seed(), which was added to 
"common/fdt_support.c".

There are 3 callers:
sec_firmware_init()->fdt_fixup_kaslr_seed()
do_kaslr_seed()->fdt_fixup_kaslr_seed()
image_setup_libfdt()->fdt_tpm_kaslr_seed->fdt_fixup_kaslr_seed()

I think the ask is to create a common API that uses the ofnode API.  So, 
instead of fdt_fixup_kaslr_seed() I can create 
ofnode_fixup_kaslr_seed()?  Where should it live?  Are you also wanting 
the callers (eg. fdt_tpm_kaslr_seed, fdt_fixup_kaslr) to take oftree as 
input too?

>
>>   {
>> -       int nodeoffset;
>> -       int err, ret = 0;
>> -       u8 rand[8];
>> +       int ret = 0;
>>
>>   #if defined(CONFIG_ARMV8_SEC_FIRMWARE_SUPPORT)
>> +       u8 rand[8];
>> +
>>          /* Check if random seed generation is  supported */
>>          if (sec_firmware_support_hwrng() == false) {
>>                  printf("WARNING: SEC firmware not running, no kaslr-seed\n");
>> -               return 0;
>> +               return -EOPNOTSUPP;
>>          }
>>
>>          err = sec_firmware_get_random(rand, 8);
>>          if (err < 0) {
>>                  printf("WARNING: No random number to set kaslr-seed\n");
>> -               return 0;
>> -       }
>> -
>> -       err = fdt_check_header(fdt);
>> -       if (err < 0) {
>> -               printf("fdt_chosen: %s\n", fdt_strerror(err));
>> -               return 0;
>> +               return ret;
>>          }
>>
>> -       /* find or create "/chosen" node. */
>> -       nodeoffset = fdt_find_or_add_subnode(fdt, 0, "chosen");
>> -       if (nodeoffset < 0)
>> -               return 0;
>> -
>> -       err = fdt_setprop(fdt, nodeoffset, "kaslr-seed", rand,
>> -                                 sizeof(rand));
>> -       if (err < 0) {
>> -               printf("WARNING: can't set kaslr-seed %s.\n",
>> -                      fdt_strerror(err));
>> -               return 0;
>> -       }
>> -       ret = 1;
>> +       ret = fdt_fixup_kaslr_seed(fdt, rand, sizeof(rand));
>>   #endif
>>
>>          return ret;
>> diff --git a/common/fdt_support.c b/common/fdt_support.c
>> index 5e49078f8c..35d4f26dbd 100644
>> --- a/common/fdt_support.c
>> +++ b/common/fdt_support.c
>> @@ -631,6 +631,37 @@ void fdt_fixup_ethernet(void *fdt)
>>          }
>>   }
>>
>> +/*
>> + * fdt_fix_kaslr_seed - Add kalsr-seed node in Device tree
>> + * @fdt:               Device tree
>> + * @eret:              0 for success
>> + */
>> +int fdt_fixup_kaslr_seed(void *fdt, const u8 *seed, int len)
>> +{
>> +       int nodeoffset;
>> +       int err;
>> +
>> +       err = fdt_check_header(fdt);
>> +       if (err < 0) {
>> +               printf("fdt_chosen: %s\n", fdt_strerror(err));
>> +               return err;
>> +       }
>> +
>> +       /* find or create "/chosen" node. */
>> +       nodeoffset = fdt_find_or_add_subnode(fdt, 0, "chosen");
>> +       if (nodeoffset < 0)
>> +               return -ENOENT;
>> +
>> +       err = fdt_setprop(fdt, nodeoffset, "kaslr-seed", seed, len);
>> +       if (err < 0) {
>> +               printf("WARNING: can't set kaslr-seed %s.\n",
>> +                      fdt_strerror(err));
>> +               return err;
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>>   int fdt_record_loadable(void *blob, u32 index, const char *name,
>>                          uintptr_t load_addr, u32 size, uintptr_t entry_point,
>>                          const char *type, const char *os, const char *arch)
>> diff --git a/include/fdt_support.h b/include/fdt_support.h
>> index 2cd8366898..d74ef4e0a7 100644
>> --- a/include/fdt_support.h
>> +++ b/include/fdt_support.h
>> @@ -121,6 +121,9 @@ static inline int fdt_fixup_memory_banks(void *blob, u64 start[], u64 size[],
>>   #endif
>>
>>   void fdt_fixup_ethernet(void *fdt);
>> +
>> +int fdt_fixup_kaslr_seed(void *fdt, const u8 *seed, int len);
> Please get in the habit of adding full comments to exported functions.
>
>> +
>>   int fdt_find_and_setprop(void *fdt, const char *node, const char *prop,
>>                           const void *val, int len, int create);
>>   void fdt_fixup_qe_firmware(void *fdt);
>> --
>> 2.40.0
>>
> Regards,
> Simon
>
>