https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95571
Bug ID: 95571 Summary: xtensa stack unwinding doesn't work well with asynchronous register spilling Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: jcmvbkbc at gcc dot gnu.org Target Milestone: --- Xtensa architecture with variable register windows store registers of the spilled register windows in two separate locations: registers a0-a3 of the current function caller are stored right below the stack pointer of current function in the location known as a base save area, and the registers a4-a7 (or a4-a11) are stored in the top of the caller's stack frame in a location known as an extra save area, right under the base save area of is own caller. To spill or restore registers a4-a7/a11 of the function its caller stack pointer is used to find its extra save area. Interrupt handlers on bare metal xtensa targets spill registers of all active register windows in the interrupted code except the current topmost window. Stack unwinding code for xtensa copies base save area of the context being installed into the base save area under the _Unwind_RaiseException stack pointer so that return from _Unwind_RaiseException reload registers of that context. However when it happens in a function called from _Unwind_RaiseException an interrupt can spill registers of the _Unwind_RaiseException to its extra save area. The location of this area is lost once base save area under the _Unwind_RaiseException stack pointer is overwritten resulting in bogus values being reloaded into registers a4-a7 usually resulting in a crash.