ArmPkg: StMM: Use x29 register to store stack address #11027
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Now that the use of 18 registers for FF-A is supported. Registers from x0-x17 can be used by FF-A to return call results. StMM also uses registers x19-x23 to store SPMC boot information. Use the x29 register to store the stack address instead of x12 to avoid it being clobbered by FF-A calls. The x29 is normally used as a Frame Pointer Register, but it's not used as such in this context, so it could be used here. Signed-off-by: Mohamed Gamal Morsy <[email protected]>
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Description
Now that the use of 18 registers for FF-A is supported. Registers from x0-x17 can be used by FF-A to return call results. StMM also uses registers x19-x23 to store SPMC boot information.
Use the x29 register to store the stack address instead of x12 to avoid it being clobbered by FF-A calls.
The x29 register is normally used as a Frame Pointer Register, but it's not used as such in this context, so it could be used here.
How This Was Tested
Tested running rust-spmc as an EL-1 SPMC
Integration Instructions
N/A