linux-kernel - Re: [RFC PATCH v2 1/3] powerpc/prom_init: Replace linux,sml-base/sml-size with linux,sml-log

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Message-ID: <2c9dc099-f450-40af-9723-27ca2b69afdc@linux.ibm.com>
Date: Mon, 11 Mar 2024 15:10:40 -0400
From: Stefan Berger <stefanb@...ux.ibm.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Cc: "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "rnsastry@...ux.ibm.com" <rnsastry@...ux.ibm.com>,
        "jsnitsel@...hat.com" <jsnitsel@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "peterhuewe@....de" <peterhuewe@....de>,
        "viparash@...ibm.com" <viparash@...ibm.com>
Subject: Re: [RFC PATCH v2 1/3] powerpc/prom_init: Replace
 linux,sml-base/sml-size with linux,sml-log



On 3/11/24 13:24, Christophe Leroy wrote:
> 
> 
> Le 11/03/2024 à 14:20, Stefan Berger a écrit :
>> linux,sml-base holds the address of a buffer with the TPM log. This
>> buffer may become invalid after a kexec. To avoid accessing an invalid
>> address or corrupted buffer, embed the whole TPM log in the device tree
>> property linux,sml-log. This helps to protect the log since it is
>> properly carried across a kexec soft reboot with both of the kexec
>> syscalls.
>>
>> Avoid having the firmware ingest the whole TPM log when calling
>> prom_setprop but only create the linux,sml-log property as a place holder.
>> Insert the actual TPM log during the tree flattening phase.
>>
>> Fixes: 4a727429abec ("PPC64: Add support for instantiating SML from Open Firmware")
>> Suggested-by: Michael Ellerman <mpe@...erman.id.au>
>> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
>> ---

>> @@ -2645,6 +2645,17 @@ static void __init scan_dt_build_struct(phandle node, unsigned long *mem_start,
>>    		}
>>    		prev_name = sstart + soff;
>>    
>> +		if (!prom_strcmp("linux,sml-log", pname)) {
>> +			/* push property head */
>> +			dt_push_token(OF_DT_PROP, mem_start, mem_end);
>> +			dt_push_token(sml_size, mem_start, mem_end);
>> +			dt_push_token(soff, mem_start, mem_end);
>> +			/* push property content */
>> +			valp = make_room(mem_start, mem_end, sml_size, 1);
>> +			memcpy(valp, (void *)sml_base, sml_size);
> 
> You can't cast a u64 into a pointer. If sml_base is an address, it must
> be declared as an unsigned long.
> 
> Build with pmac32_defconfig :
> 
>     CC      arch/powerpc/kernel/prom_init.o
> arch/powerpc/kernel/prom_init.c: In function 'scan_dt_build_struct':
> arch/powerpc/kernel/prom_init.c:2663:38: error: cast to pointer from
> integer of different size [-Werror=int-to-pointer-cast]
>    2663 |                         memcpy(valp, (void *)sml_base, sml_size);
>         |                                      ^
> cc1: all warnings being treated as errors
> make[4]: *** [scripts/Makefile.build:243:
> arch/powerpc/kernel/prom_init.o] Error 1

Next round will have this block under #ifdef CONFIG_PPC64.

Thanks.