Etm4 t32 return address fix#92
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For M-profile tracing, the preferred exception return address may lie within a restartable 32-bit T32 instruction. The decoder searches for the preferred return address at instruction boundaries. When the address lies within a 32-bit Thumb instruction, it can be skipped, causing tracing to continue past the exception return point and emit an incorrect instruction range. Detect this case and stop tracing at the preferred return address when it falls within the current Thumb-2 instruction. Add regression snapshot tests covering exception return addresses at an instruction boundary, within a 32-bit T32 instruction, and at the next instruction boundary to validate the behaviour and prevent future regressions. Signed-off-by: Sayani Halder <sayani.halder@arm.com>
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opencsd: etm4: handle exception return addresses inside T32 instructions
When processing an exception packet, the ETMv4 decoder traces to the
preferred exception return address using traceInstrToWP(). For M-profile
devices, the preferred exception return address may lie within a
restartable or interrupt-continuable 32-bit T32 instruction.
The decoder advances by instruction boundaries while searching for the
target address. When the preferred return address lies inside a 32-bit
Thumb instruction, the address is skipped and never matched directly,
causing tracing to continue past the exception return point and emit an
incorrect instruction range.
Detect this case and treat the preferred return address as reached when
it falls within the current decoded Thumb-2 instruction, ensuring the
instruction range reported before the exception matches the expected
execution flow.
Add regression snapshot tests covering exception return addresses at an
instruction boundary, within a 32-bit T32 instruction, and at the next
instruction boundary to validate the behaviour and prevent future
regressions.
Signed-off-by: Your Name your.email@example.com