Jordan wrote:
>>> So, is it safe to adjust rbp? Unknown. It may not be if rbp is not
>>> used as a frame pointer. Is it safe to *not* adjust rbp and
>>> potentially allow the old temp ram stack to be used? Unknown.
Andrew wrote:
> Looks like OvmfPkg uses SetJump()/LongJump() to change the stack.
>
> //
> // Use SetJump()/LongJump() to switch to a new stack.
> //
> if (SetJump (&JumpBuffer) == 0) {
> #if defined (MDE_CPU_IA32)
> JumpBuffer.Esp = JumpBuffer.Esp + DebugAgentContext.StackMigrateOffset;
> JumpBuffer.Ebp = JumpBuffer.Ebp + DebugAgentContext.StackMigrateOffset;
> #endif
> #if defined (MDE_CPU_X64)
> JumpBuffer.Rsp = JumpBuffer.Rsp + DebugAgentContext.StackMigrateOffset;
> JumpBuffer.Rbp = JumpBuffer.Rbp + DebugAgentContext.StackMigrateOffset;
> #endif
> LongJump (&JumpBuffer, (UINTN)-1);
> }
>
> SaveAndSetDebugTimerInterrupt (OldStatus);
>
> return EFI_SUCCESS;
> }
>
> But given the above code is C code RBP is going to be restored on return.
> This would seem to imply that the adjusting of the callers RBP is not
> required? [...]
The Ebp/Rbp assignments were added in a separate bugfix, namely
https://github.com/tianocore/edk2/commit/89796c69d9fd
Laszlo
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