________________________________________ > From: Stefan Berger <stefanb@xxxxxxxxxxxxx> > Sent: 07 July 2022 10:50 PM > To: kexec@xxxxxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-integrity@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linuxppc-dev@xxxxxxxxxxxxxxxx > Cc: nayna@xxxxxxxxxxxxx; Nageswara R Sastry; mpe@xxxxxxxxxxxxxx; Stefan Berger; Rob Herring; Frank Rowand; Eric Biederman > Subject: [PATCH v6 6/6] tpm/kexec: Duplicate TPM measurement log in of-tree for kexec > The memory area of the TPM measurement log is currently not properly > duplicated for carrying it across kexec when an Open Firmware > Devicetree is used. Therefore, the contents of the log get corrupted. > Fix this for the kexec_file_load() syscall by allocating a buffer and > copying the contents of the existing log into it. The new buffer is > preserved across the kexec and a pointer to it is available when the new > kernel is started. To achieve this, store the allocated buffer's address > in the flattened device tree (fdt) under the name linux,tpm-kexec-buffer > and search for this entry early in the kernel startup before the TPM > subsystem starts up. Adjust the pointer in the of-tree stored under > linux,sml-base to point to this buffer holding the preserved log. The TPM > driver can then read the base address from this entry when making the log > available. Invalidate the log by removing 'linux,sml-base' from the > devicetree if anything goes wrong with updating the buffer. > Use subsys_initcall() to call the function to restore the buffer even if > the TPM subsystem or driver are not used. This allows the buffer to be > carried across the next kexec without involvement of the TPM subsystem > and ensures a valid buffer pointed to by the of-tree. > Use the subsys_initcall(), rather than an ealier initcall, since > page_is_ram() in get_kexec_buffer() only starts working at this stage. > Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx> > Cc: Rob Herring <robh+dt@xxxxxxxxxx> > Cc: Frank Rowand <frowand.list@xxxxxxxxx> > Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx> > --- > v6: > - Define prototype for tpm_add_kexec_buffer under same config options > as drivers/of/kexec.c is compiled, provide inline function otherwise. > (kernel test robot) Tested-by: Nageswara R Sastry <rnsastry@xxxxxxxxxxxxx>
