On Fri, Dec 5, 2025, at 14:45, Harshal Dev wrote:
On 12/4/2025 6:57 PM, Jens Wiklander wrote:
On Thu, Dec 4, 2025 at 11:17 AM Arnd Bergmann arnd@kernel.org wrote:
The only user-space client which is currently using this ABI (as per our knowledge) is the libqcomtee library: https://github.com/quic/quic-teec/blob/main/libqcomtee/src/linux/tee.h#L432
If I understand Arnd's concern correctly, if a compiler used to build the user-space client skips the padding for tee_ioctl_object_invoke_arg, it could lead to issues.
Let's wait for Amir's view here as well, however I do think the explicit padding would benefit here.
The problem is much narrower: as the amount of padding is determined by the architecture specific ABI, kernel and userspace on the same architecture always agree, and specifically 32-bit Arm userspace and 64-bit Arm userspace (aarch64) also have the same rules, so there is no problem on Qualcomm's platforms even with compat 32-bit userspace.
The only actual ABI problem would happen on 32-bit x86 (i386) userspace running on a 64-bit x86 kernel, since i386-linux compilers have different alignment rules from most other architectures.
Arnd