[REBASE & FF] Add Stack Overflow Hint in Exception Handlers#1554
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cfernald
approved these changes
Jun 3, 2026
makubacki
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Jun 5, 2026
Currently, only double faults use a separate stack. However, a stack overflow manifests as a page fault, so taking a stack overflow causes a double fault. This makes it harder to reason about what the fault was. This commit instead using a separate stack for x64 page faults, aligning with the aarch64 side. This is in preparation for giving better information about stack overflows in the exception handlers. Signed-off-by: Oliver Smith-Denny <osde@microsoft.com>
Currently, stack overflows show up as page faults in the exception handlers. This can make it hard to identify when a different page fault has occurred. This commit introduces a heuristic to hint that a stack overflow likely occurred in the exception handler. It checks if the faulting address is on the same page as or one page lower than the stack pointer. In some cases, the stack pointer is incremented first, then data is written (in which case the faulting address is on the same page as the stack pointer) and in other cases the data is written before the stack pointer is decremented (so the faulting address is on the page below the stack pointer). A pretty message is then printed to indicate a stack overflow occurred. Signed-off-by: Oliver Smith-Denny <osde@microsoft.com>
The EfiExceptionStackTrace trait is an internal trait that originally was just used so the common exception handler can use arch specific stack trace dumping. However, this was expanded to also include dumping a page table walk, so the name is not accurate. Signed-off-by: Oliver Smith-Denny <osde@microsoft.com>
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Description
Stack overflows show up as page faults in the exception handler, which can be hard to distinguish from other kinds of page faults. This PR contains three commits to provide a hint that a stack overflow occurred.
x64: IDT: Use a Separate Stack for Page Fault Exceptions
Currently, only double faults use a separate stack. However, a stack overflow manifests as a page fault, so taking a stack overflow causes a double fault. This makes it harder to reason about what the fault was.
This commit instead using a separate stack for x64 page faults, aligning with the aarch64 side. This is in preparation for giving better information about stack overflows in the exception handlers.
exception handlers: Print Stack Overflow Hint
Currently, stack overflows show up as page faults in the exception handlers. This can make it hard to identify when a different page fault has occurred.
This commit introduces a heuristic to hint that a stack overflow likely occurred in the exception handler. It checks if the faulting address is on the same page as or one page lower than the stack pointer. In some cases, the stack pointer is incremented first, then data is written (in which case the faulting address is on the same page as the stack pointer) and in other cases the data is written before the stack pointer is decremented (so the faulting address is on the page below the stack pointer).
A pretty message is then printed to indicate a stack overflow occurred.
internal_cpu: Rename EfiExceptionStackTrace Trait
The EfiExceptionStackTrace trait is an internal trait that originally was just used so the common exception handler can use arch specific stack trace dumping.
However, this was expanded to also include dumping a page table walk, so the name is not accurate.
How This Was Tested
In Q35 and SBSA testing stack overflows which now look like:
Integration Instructions
N/A.