The Fast Models provide a non-volatile counter component, which is used
in the Trusted Board Boot implementation to protect against rollback
attacks.
This component comes in 2 versions (see [1]).
- Version 0 is the default and models a locked non-volatile counter,
whose value is fixed.
- Version 1 of the counter may be incremented in a monotonic fashion.
plat_set_nv_ctr() must cope with both versions. This is achieved by:
1) Attempting to write the new value in the counter.
2) Reading the value back.
3) If there is a mismatch, we know the counter upgrade failed.
When using version 0 of the counter, no upgrade is possible so the
function is expected to fail all the time. However, the code is
missing a compiler barrier between the write operation and the next
read. Thus, the compiler may optimize and remove the read operation on
the basis that the counter value has not changed. With the default
optimization level used in TF-A (-Os), this is what's happening.
The fix introduced in this patch marks the write and subsequent read
accesses to the counter as volatile, such that the compiler makes no
assumption about the value of the counter.
Note that the comment above plat_set_nv_ctr() was clearly stating
that when using the read-only version of the non-volatile counter,
"we expect the values in the certificates to always match the RO
values so that this function is never called". However, the fact that
the counter value was read back seems to contradict this comment, as
it is implementing a counter-measure against misuse of the
function. The comment has been reworded to avoid any confusion.
Without this patch, this bug may be demonstrated on the Base AEM FVP:
- Using version 0 of the non-volatile counter (default version).
- With certificates embedding a revision number value of 32
(compiling TF-A with TFW_NVCTR_VAL=32).
In this configuration, the non-volatile counter is tied to value 31 by
default. When BL1 loads the Trusted Boot Firmware certificate, it
notices that the two values do not match and tries to upgrade the
non-volatile counter. This write operation is expected to fail
(because the counter is locked) and the function is expected to return
an error but it succeeds instead.
As a result, the trusted boot does not abort as soon as it should and
incorrectly boots BL2. The boot is finally aborted when BL2 verifies
the BL31 image and figures out that the version of the SoC Firmware
Key Certificate does not match. On Arm platforms, only certificates
signed with the Root-of-Trust Key may trigger an upgrade of the
non-volatile Trusted counter.
[1] https://developer.arm.com/docs/100964/1160/fast-models-components/peripheral-components/nonvolatilecounter
Change-Id: I9979f29c23b47b338b9b484013d1fb86c59db92f
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
From now on, platform_def.h must include any header with definitions that
are platform-specific (like arm_def.h) and the included headers mustn't
include back platform_def.h, and shouldn't be used by other files. Only
platform_def.h should be included in other files. This will ensure that all
needed definitions are present, rather than needing to include all the
headers in all the definitions' headers just in case.
This also prevents problems like cyclic dependencies.
Change-Id: I9d3cf4d1de4b956fa035c79545222697acdaf5ca
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Enforce full include path for includes. Deprecate old paths.
The following folders inside include/lib have been left unchanged:
- include/lib/cpus/${ARCH}
- include/lib/el3_runtime/${ARCH}
The reason for this change is that having a global namespace for
includes isn't a good idea. It defeats one of the advantages of having
folders and it introduces problems that are sometimes subtle (because
you may not know the header you are actually including if there are two
of them).
For example, this patch had to be created because two headers were
called the same way: e0ea0928d5 ("Fix gpio includes of mt8173 platform
to avoid collision."). More recently, this patch has had similar
problems: 46f9b2c3a2 ("drivers: add tzc380 support").
This problem was introduced in commit 4ecca33988 ("Move include and
source files to logical locations"). At that time, there weren't too
many headers so it wasn't a real issue. However, time has shown that
this creates problems.
Platforms that want to preserve the way they include headers may add the
removed paths to PLAT_INCLUDES, but this is discouraged.
Change-Id: I39dc53ed98f9e297a5966e723d1936d6ccf2fc8f
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
Rule 8.4: A compatible declaration shall be visible when
an object or function with external linkage is defined
Fixed for:
make DEBUG=1 PLAT=fvp LOG_LEVEL=50 all
Change-Id: I7c2ad3f5c015411c202605851240d5347e4cc8c7
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>
The header tbbr_oid.h contains OIDs obtained by ARM Ltd.
so there is no good reason to use platform_oid.h
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
To make software license auditing simpler, use SPDX[0] license
identifiers instead of duplicating the license text in every file.
NOTE: Files that have been imported by FreeBSD have not been modified.
[0]: https://spdx.org/
Change-Id: I80a00e1f641b8cc075ca5a95b10607ed9ed8761a
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>
Replaced placeholder implementation of plat_set_nv_ctr for FVP
platforms by a working one.
On FVP, the mapping of region DEVICE2 has been changed from RO to RW
to prevent exceptions when writing to the NV counter, which is
contained in this region.
Change-Id: I56a49631432ce13905572378cbdf106f69c82f57
Sandrine Bailleux
Antonio Nino Diaz
Roberto Vargas
Masahiro Yamada
dp-arm