On Wed, May 06, 2020 at 10:50:04PM -0700, Prakhar Srivastava wrote: > Hi Mark, Please don't top post. > This patch set currently only address the Pure DT implementation. > EFI and ACPI implementations will be posted in subsequent patchsets. > > The logs are intended to be carried over the kexec and once read the > logs are no longer needed and in prior conversation with James( > https://lore.kernel.org/linux-arm-kernel/0053eb68-0905-4679-c97a-00c5cb6f1abb@xxxxxxx/) > the apporach of using a chosen node doesn't > support the case. > > The DT entries make the reservation permanent and thus doesnt need kernel > segments to be used for this, however using a chosen-node with > reserved memory only changes the node information but memory still is > reserved via reserved-memory section. I think Mark's point was whether it needs to be permanent. We don't hardcode the initrd address for example. > On 5/5/20 2:59 AM, Mark Rutland wrote: > > Hi Prakhar, > > > > On Mon, May 04, 2020 at 01:38:27PM -0700, Prakhar Srivastava wrote: > > > IMA during kexec(kexec file load) verifies the kernel signature and measures What's IMA? > > > the signature of the kernel. The signature in the logs can be used to verfiy the > > > authenticity of the kernel. The logs don not get carried over kexec and thus > > > remote attesation cannot verify the signature of the running kernel. > > > > > > Introduce an ABI to carry forward the ima logs over kexec. > > > Memory reserved via device tree reservation can be used to store and read > > > via the of_* functions. > > > > This flow needs to work for: > > > > 1) Pure DT > > 2) DT + EFI memory map > > 3) ACPI + EFI memory map > > > > ... and if this is just for transiently passing the log, I don't think > > that a reserved memory region is the right thing to use, since they're > > supposed to be more permanent. > > > > This sounds analogous to passing the initrd, and should probably use > > properties under the chosen node (which can be used for all three boot > > flows above). > > > > For reference, how big is the IMA log likely to be? Does it need > > physically contiguous space? > > It purely depends on the policy used and the modules/files that are accessed > for my local testing over a kexec session the log in > about 30KB. > > Current implementation expects enough contiguous memory to allocated to > carry forward the logs. If the log size exceeds the reserved memory the > call will fail. > > Thanks, > Prakhar Srivastava > > > > Thanks, > > Mark. > > > > > > > > Reserved memory stores the size(sizeof(size_t)) of the buffer in the starting > > > address, followed by the IMA log contents. > > > > > > Tested on: > > > arm64 with Uboot > > > > > > Prakhar Srivastava (2): > > > Add a layer of abstraction to use the memory reserved by device tree > > > for ima buffer pass. > > > Add support for ima buffer pass using reserved memory for arm64 kexec. > > > Update the arch sepcific code path in kexec file load to store the > > > ima buffer in the reserved memory. The same reserved memory is read > > > on kexec or cold boot. > > > > > > arch/arm64/Kconfig | 1 + > > > arch/arm64/include/asm/ima.h | 22 ++++ > > > arch/arm64/include/asm/kexec.h | 5 + > > > arch/arm64/kernel/Makefile | 1 + > > > arch/arm64/kernel/ima_kexec.c | 64 ++++++++++ > > > arch/arm64/kernel/machine_kexec_file.c | 1 + > > > arch/powerpc/include/asm/ima.h | 3 +- > > > arch/powerpc/kexec/ima.c | 14 ++- > > > drivers/of/Kconfig | 6 + > > > drivers/of/Makefile | 1 + > > > drivers/of/of_ima.c | 165 +++++++++++++++++++++++++ > > > include/linux/of.h | 34 +++++ > > > security/integrity/ima/ima_kexec.c | 15 ++- > > > 13 files changed, 325 insertions(+), 7 deletions(-) > > > create mode 100644 arch/arm64/include/asm/ima.h > > > create mode 100644 arch/arm64/kernel/ima_kexec.c > > > create mode 100644 drivers/of/of_ima.c > > > > > > -- > > > 2.25.1 > > >
