On 10/22/20 8:46 PM, Thiago Jung Bauermann wrote:
Hi Thiago,
Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx> writes:
On 10/20/20 8:17 PM, Mimi Zohar wrote:
On Tue, 2020-10-20 at 19:25 -0700, Lakshmi Ramasubramanian wrote:
On 10/20/20 1:00 PM, Mimi Zohar wrote:
Hi Lakshmi,
On Wed, 2020-09-30 at 13:59 -0700, Lakshmi Ramasubramanian wrote:
The functions remove_ima_buffer() and delete_fdt_mem_rsv() that handle
carrying forward the IMA measurement logs on kexec for powerpc do not
have architecture specific code, but they are currently defined for
powerpc only.
remove_ima_buffer() and delete_fdt_mem_rsv() are used to remove
the IMA log entry from the device tree and free the memory reserved
for the log. These functions need to be defined even if the current
kernel does not support carrying forward IMA log across kexec since
the previous kernel could have supported that and therefore the current
kernel needs to free the allocation.
Rename remove_ima_buffer() to remove_ima_kexec_buffer().
Define remove_ima_kexec_buffer() and delete_fdt_mem_rsv() in kernel.
A later patch in this series will use these functions to free
the allocation, if any, made by the previous kernel for ARM64.
Define FDT_PROP_IMA_KEXEC_BUFFER for the chosen node, namely
"linux,ima-kexec-buffer", that is added to the DTB to hold
the address and the size of the memory reserved to carry
the IMA measurement log.
Co-developed-by: Prakhar Srivastava <prsriva@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Prakhar Srivastava <prsriva@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx> error: implicit declaration of function 'delete_fdt_mem_rsv' [-Werror,-Wimplicit-function-declaration]
Much better! This version limits unnecessarily changing the existing
code to adding a couple of debugging statements, but that looks to be
about it.
Yes Mimi - that's correct.
Based on Chester Lin's "ima_arch" support for arm64 discussion, the IMA generic
EFI support will be defined in ima/ima-efi.c. Similarly, I think it would make sense to put the generic device tree support in ima/ima_kexec_fdt.c or ima/ima_fdt.c, as opposed to kernel/. (Refer to my comments on 2/4 about the new file named ima_kexec_fdt.c.)
The functions remove_ima_kexec_buffer() and delete_fdt_mem_rsv(), which
are defined in kernel/ima_kexec.c and kernel/kexec_file_fdt.c
respectively, are needed even when CONFIG_IMA is not defined. These
functions need to be called by the current kernel to free the ima kexec
buffer resources allocated by the previous kernel. This is the reason,
these functions are defined under "kernel" instead of
"security/integrity/ima".
If there is a better location to move the above C files, please let me
know. I'll move them.
Freeing the previous kernel measurement list is currently called from
ima_load_kexec_buffer(), only after the measurement list has been
restored. The only other time the memory is freed is when the
allocated memory size isn't sufficient to hold the measurement list,
which could happen if there is a delay between loading and executing
the kexec.
There are two "free" operations we need to perform with respect to ima buffer on
kexec:
1, The ima_free_kexec_buffer() called from ima_load_kexec_buffer() - the one you
have stated above.
Here we remove the "ima buffer" node from the "OF" tree and free the memory
pages that were allocated for the measurement list.
This one is already present in ima and there's no change in that in my patches.
2, The other one is remove_ima_kexec_buffer() called from setup_ima_buffer()
defined in "arch/powerpc/kexec/ima.c"
This function removes the "ima buffer" node from the "FDT" and also frees the
physical memory reserved for the "ima measurement list" by the previous kernel.
This "free" operation needs to be performed even if the current kernel does not
support IMA kexec since the previous kernel could have passed the IMA
measurement list (in FDT and reserved physical memory).
For this reason, remove_ima_kexec_buffer() cannot be defined in "ima" but some
other place which will be built even if ima is not enabled. I chose to define
this function in "kernel" since that is guaranteed to be always built.
thanks,
-lakshmi
That is true. I believe a more fitting place for these functions is
drivers/of/fdt.c rather than these new files in kernel/. Both CONFIG_PPC
and CONFIG_ARM64 select CONFIG_OF and CONFIG_OF_FLATTREE (indirectly,
via CONFIG_OF_EARLY_FLATTREE) so they will both build that file.
I moved the above mentioned functions to drivers/of/fdt.c => it works.
But I am not sure if "drivers/of" is the right place - this driver is
handling data from firmware and building FDT. I do not see any kexec
related operations being handled by this driver in the current
implementation.
Also, being a driver can it be loaded/unloaded on-demand? If yes, it may
not be available when "ima kexec" calls are needed.
@Rob Herring - what do you think?
thanks,
-lakshmi
