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Documented the fact that the prefix can prot_call(main) without

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worrying about its stack being destroyed during the Etherboot run.
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Michael Brown
2006-05-25 22:04:17 +00:00
parent 0479e9f541
commit 29340d7728
1 changed files with 9 additions and 0 deletions
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9
src/arch/i386/transitions/librm.S
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@@ -328,6 +328,15 @@ rm_ds: .word 0
* function explicitly overwrites values in ix86. Interrupt status * function explicitly overwrites values in ix86. Interrupt status
* and GDT will also be preserved. Gate A20 will be enabled. * and GDT will also be preserved. Gate A20 will be enabled.
* *
* Note that prot_call() does not rely on the real-mode stack
* remaining intact in order to return, since everything relevant is
* copied to the protected-mode stack for the duration of the call.
* In particular, this means that a real-mode prefix can make a call
* to main() which will return correctly even if the prefix's stack
* gets vapourised during the Etherboot run. (The prefix cannot rely
* on anything else on the stack being preserved, so should move any
* critical data to registers before calling main()).
*
* Parameters: * Parameters:
* function : virtual address of protected-mode function to call * function : virtual address of protected-mode function to call
* *