Hi Tom,
On 9/19/25 6:10 PM, Tom Rini wrote:
On Fri, Sep 19, 2025 at 05:50:21PM +0200, Quentin Schulz wrote:
From: Quentin Schulz <[email protected]>
It is currently possible to build an image with an OP-TEE OS (via the
TEE environment variable) without OPTEE_LIB. U-Boot will happily load
the TEE OS and the next OS (e.g. the Linux kernel).
This is an issue because on FDT-enabled devices, OP-TEE OS adds nodes to
the reserved-memory FDT node for the memory regions it just reserved for
itself. This updated is then passed to U-Boot proper which should know
better not to use memory from there. The actual issue is that without
OPTEE_LIB and OF_LIBFDT enabled, U-Boot proper will not copy those nodes
over to the next OS's FDT before starting it. This results in the next
OS's (e.g. Linux kernel) to not be aware of reserved memory, incurring
random crashes or device reboots when it tries to access secure reserved
memory area.
Signed-off-by: Quentin Schulz <[email protected]>
---
I've just lost a day trying to figure out why my board suddenly boot
loops when running a specific program in Linux userspace after updating
U-Boot. I actually inadvertently had the TEE environment variable set
for a device which doesn't actually need to run any TEE OS (so had
OPTEE_LIB disabled).
This device is Rockchip PX30-based and the image is built with binman
like all Rockchip-based devices.
The issue is that I built a U-Boot FIT with an OP-TEE OS that reserves
some memory regions for itself (via the TEE environment variable) but
U-Boot proper "forgot" to propagate those to the Linux kernel's FDT
(because of the missing OPTEE_LIB).
Unfortunately, binman doesn't seem to have access to Kconfig symbols
(grep CONFIG_ doesn't return anything meaningful and binman is either
configured through FDT nodes or via CLI arguments, c.f. cmd_binman in
the root Makefile) so I cannot try to be smart and guide the user to
the correct Kconfig option to select if TEE is set. I could add a
property based on the presence of OPTEE_LIB in rockchip-u-boot.dtsi for
example and have a custom message based on that, the issue is that I
assume all FDT-based platforms do actually need to do this dance, and
not only Rockchip.
Another option could be to add a CLI argument to binman through which
we would pass the state of OPTEE_LIB and error out the build in that
case, but that feels like opening the door to dirty hacks (though this
patch is admittedly another dirty hack :) ).
Another option is to propagate the TEE environment variable to the
preprocessor of the FDT (via dtc_cpp_flags) and then I can do
#if defined(TEE) && !IS_ENABLED(CONFIG_OPTEE_LIB)
#error "CONFIG_OPTEE_LIB must be enabled!"
#endif
but we have the same issue as above, it is then Rockchip specific and
also feels bad.
Another option is to remove the @tee-SEQ node from the binman FIT
description when OPTEE_LIB isn't set but then I would lose the nice
message when no TEE is provided:
Image 'simple-bin' is missing optional external blobs but is still functional:
tee-os
and even worse, build without any TEE OS even though I could provide one
with the TEE environment variable.
Finally, another option could be to move this hack under
arch/arm/mach-rockchip/Kconfig to make it Rockchip specific or add a
depends on ARCH_ROCKCHIP
OP-TEE OS on Aarch32 Rockchip boards doesn't actually need any of that
if SPL_OPTEE_IMAGE is set because arch/arm/mach-rockchip/sdram.c then
marks some hardcoded memory regions in RAM as holes in DRAM, which has
the same effect as reserved memory regions I guess. I assume other
platforms may use something different, so it may be casting too wide of
a net.
Does anyone have something more delicate than this sledgehammer of a
solution?
It looks like on other SoCs there's an ARCH_x wide imply/select OPTEE
(which in turn gets OPTEE_LIB), so is there a case for ARCH_ROCKCHIP &&
!ARM64 && !OPTEE ? I see you explained that 32bit has a workaround for
this already.
The issue is that on Rockchip you don't need OPTEE to be selected for
the OP-TEE OS to be integrated in the U-Boot FIT image. You simply set
the TEE environment variable to the path to the bl32 binary and it's
going to include it in the U-Boot FIT.
I think this is actually a good thing to be allowed to have the OP-TEE
OS image **without** the OPTEE driver being compiled: if I want OP-TEE
OS to be loaded in the system, this will be done by the SPL by loading
the binary at a specific location in RAM, but I may not want to increase
the attack surface by enabling the OP-TEE driver in U-Boot if I don't
need to interact with OP-TEE OS from U-Boot at all.
The Aarch64 Rockchip SoCs also do not require OP-TEE OS to work (but I
**think** Aarch32 SoCs do?). "imply" in that case would not be enough
because we would still be able to include the OP-TEE OS image in the
U-Boot FIT without OPTEE driver compiled in (and thus OPTEE_LIB).
"select" would be too strong, because we really don't need OP-TEE OS (or
rather its driver, but the latter kind of implies the former) to be in
the image in order for the kernel to work just fine.
It all boils down to the ability to add OP-TEE OS to U-Boot FIT via the
TEE environment variable without changing the defconfig (i.e. it's
optional). We could make the @tee-SEQ node in
arch/arm/dts/rockchip-u-boot.dtsi presence depend on OPTEE_LIB for
example, but then we wouldn't be able to tell the user that the TEE OS
image is missing. Also, this would limit TEE OS to OP-TEE OS (which I
assume is probably what everybody is using on Rockchip but we could be
using something else technically?). That may be an acceptable limitation
though!
As for forcing OPTEE_LIB on Aarch32 Rockchip SoCs on, this OPTEE_LIB
thing relies on OP-TEE OS patching the DTB passed to U-Boot proper so
that the reserved memory nodes for OP-TEE are made explicit. I somehow
doubt this is necessarily handled by OP-TEE blobs from Rockchip? Which
means that I'm not sure that switching the hardcoded implementation to
use the logic in OPTEE_LIB will be enough.
This also reminds me that TF-A blobs from Rockchip (used to?) crash for
some DTBs, which was worked around by simply just no passing the DTB to
TF-A (see SPL_ATF_NO_PLATFORM_PARAM), which I assume means OP-TEE OS
doesn't have access to a DTB so cannot patch it. I'm not sure how (if!)
it is handled by U-Boot in that case.
Cheers,
Quentin
