The issue described involves QEMU stalling when running a specific test under different versions, particularly starting from 2.8. The problem occurs during execution and relates to an instruction (`add r4, pc, r4`) where the program hangs.

Step-by-step explanation:

1. **Understanding the Problem**: The user reports that GCC sanitizer tests time out when run using QEMU-arm starting from version 2.8, whereas they worked with version 2.7.

2. **Reproduction Steps**: They provided a test case and libraries to reproduce the issue, which involves running `qemu-arm` with specific options.

3. **Debugging Information**: The `-d in_asm` option shows that the program stalls at an `add` instruction: `0x40b6eb44: e08f4004 add r4, pc, r4`.

4. **Analyzing the Stall**: The stall suggests that QEMU is not correctly emulating this particular ARM instruction or handling it in a way that causes an infinite loop or indefinite pause.

5. **Classification**: The issue revolves around a specific CPU instruction causing QEMU to hang, which falls under "instruction" errors in the context of QEMU's bug categorization.

Based on this analysis, the appropriate category for the bug is:

**instruction**