[PATCH v5 2/5] fdt: kaslr seed from RNG device

[Sean Edmond]

Hi Ilias, Applogies, I'm fairly new to upstream contributions and I've 
missed a few things on multi-version patch series such as this one. 
Simon has elightened about patman though (I feel a bit sheepish that I 
haven't been using this tool all along). Should I resubmit this as a new 
series to ensure prior reviews and change logs are captured?

Sean

On 2023-11-17 11:33 p.m., Ilias Apalodimas wrote:
> Hi Sean
> There are a few reviewed-by tags missing since v3/v4.  Any reason you
> dropped those? The change log doesn't mention anything
>
> Thanks
> /Ilias
>
> On Fri, 17 Nov 2023 at 04:02,<seanedmond at linux.microsoft.com>  wrote:
>> From: Dhananjay Phadke<dphadke at linux.microsoft.com>
>>
>> Add support for KASLR seed from the RNG device. Invokes dm_rng_read()
>> API to read 8-bytes of random bytes.  Performs the FDT fixup using event
>> spy.  To enable use CONFIG_KASLR_RNG_SEED
>>
>> Signed-off-by: Dhananjay Phadke<dphadke at linux.microsoft.com>
>> Signed-off-by: Drew Kluemke<ankluemk at microsoft.com>
>> Signed-off-by: Sean Edmond<seanedmond at microsoft.com>
>> ---
>>   boot/fdt_support.c | 36 ++++++++++++++++++++++++++++++++++++
>>   lib/Kconfig        |  7 +++++++
>>   2 files changed, 43 insertions(+)
>>
>> diff --git a/boot/fdt_support.c b/boot/fdt_support.c
>> index 49d14a949be..12defcf645c 100644
>> --- a/boot/fdt_support.c
>> +++ b/boot/fdt_support.c
>> @@ -12,7 +12,10 @@
>>   #include <log.h>
>>   #include <mapmem.h>
>>   #include <net.h>
>> +#include <rng.h>
>>   #include <stdio_dev.h>
>> +#include <dm/device.h>
>> +#include <dm/uclass.h>
>>   #include <dm/ofnode.h>
>>   #include <linux/ctype.h>
>>   #include <linux/types.h>
>> @@ -650,6 +653,39 @@ int fdt_fixup_kaslr_seed(ofnode node, const u8 *seed, int len)
>>          return 0;
>>   }
>>
>> +int fdt_rng_kaslr_seed(void *ctx, struct event *event)
>> +{
>> +       u8 rand[8] = {0};
>> +       struct udevice *dev;
>> +       int ret;
>> +       oftree tree = event->data.ft_fixup.tree;
>> +       ofnode root_node = oftree_root(tree);
>> +
>> +       ret = uclass_first_device_err(UCLASS_RNG, &dev);
>> +       if (ret) {
>> +               printf("ERROR: Failed to find RNG device\n");
>> +               return ret;
>> +       }
>> +
>> +       ret = dm_rng_read(dev, rand, sizeof(rand));
>> +       if (ret) {
>> +               printf("ERROR: RNG read failed, ret=%d\n", ret);
>> +               return ret;
>> +       }
>> +
>> +       ret = fdt_fixup_kaslr_seed(root_node, rand, sizeof(rand));
>> +       if (ret) {
>> +               printf("ERROR: failed to add kaslr-seed to fdt\n");
>> +               return ret;
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +#if defined(CONFIG_KASLR_RNG_SEED)
>> +EVENT_SPY(EVT_FT_FIXUP, fdt_rng_kaslr_seed);
>> +#endif
>> +
>>   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/lib/Kconfig b/lib/Kconfig
>> index 19649517a39..4f5dfc00d6f 100644
>> --- a/lib/Kconfig
>> +++ b/lib/Kconfig
>> @@ -477,6 +477,13 @@ config VPL_TPM
>>            for the low-level TPM interface, but only one TPM is supported at
>>            a time by the TPM library.
>>
>> +config KASLR_RNG_SEED
>> +       bool "Use RNG driver for KASLR random seed"
>> +       depends on DM_RNG
>> +       help
>> +         This enables support for using the RNG driver as entropy source for
>> +         KASLR seed populated in kernel's device tree.
>> +
>>   endmenu
>>
>>   menu "Android Verified Boot"
>> --
>> 2.42.0
>>