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<think>
Okay, so I'm trying to figure out whether this bug report is user-mode or system-mode related. Let me break it down step by step.
The issue is about the ARM v8.3a pauth instructions not working correctly in QEMU. The test code uses two pauth instructions: paciasp and autiasp. Paciasp signs the LR (link register) with a key and sp as context, while autiasp verifies this signature.
In the test scenario, they run the program and corrupt the LR just before autiasp executes. They expected that when autiasp runs, it would detect the corruption and place an invalid pointer in LR. However, instead, autiasp successfully authenticated the pointer despite the corruption, which shouldn't have happened.
The user provided traces showing that the pauth_computepac function isn't handling truncation properly. For example, with specific inputs, the top_bit and bot_bit remain the same even after truncating parts of the address. This suggests a flaw in how QEMU computes PAC (Pointer Authentication Code) values for different key types.
Now, considering whether this is a user-mode or system-mode issue: user-mode issues typically involve application-level code running without special privileges, while system-mode involves higher privilege levels like kernel code, device drivers, or hardware interactions.
In this case, the problem arises from how QEMU emulates the ARM instructions, specifically the pauth operations. These instructions are part of the CPU's functionality and are used for pointer authentication in user-space applications to prevent certain types of attacks. The bug affects the computation within QEMU's emulation of these instructions.
Since the issue is with the emulator's handling of specific CPU instructions that don't require kernel privileges but are crucial for application security, it falls under how user-mode applications interact with the CPU features provided by QEMU. Therefore, this seems to be a user-mode related bug.
</think>
The bug report pertains to the incorrect handling of ARM v8.3a pauth instructions in QEMU, specifically affecting pointer authentication in user-space applications.
user
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