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[efi] Drop to TPL_APPLICATION when gathering entropy 

Commit c89a446 ("[efi] Run at TPL_CALLBACK to protect against UEFI
timers") introduced a regression in the EFI entropy gathering code.
When the EFI_RNG_PROTOCOL is not present, we fall back to using timer
interrupts (as for the BIOS build).  Since timer interrupts are
disabled at TPL_CALLBACK, WaitForEvent() fails and no entropy can be
gathered.

Fix by dropping to TPL_APPLICATION while entropy gathering is enabled.

Reported-by: Andreas Hammarskjöld <junior@2PintSoftware.com>
Tested-by: Andreas Hammarskjöld <junior@2PintSoftware.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
pull/69/head
Michael Brown 2018-03-12 10:55:28 +00:00
parent c84f9d6727
commit d8c500b794
1 changed files with 6 additions and 0 deletions
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6
src/interface/efi/efi_entropy.c
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@ -79,6 +79,9 @@ static int efi_entropy_enable ( void ) {
DBGC ( &tick, "ENTROPY %s RNG protocol\n", DBGC ( &tick, "ENTROPY %s RNG protocol\n",
( efirng ? "has" : "has no" ) ); ( efirng ? "has" : "has no" ) );
/* Drop to TPL_APPLICATION to allow timer tick event to take place */
bs->RestoreTPL ( TPL_APPLICATION );
/* Create timer tick event */ /* Create timer tick event */
if ( ( efirc = bs->CreateEvent ( EVT_TIMER, TPL_NOTIFY, NULL, NULL, if ( ( efirc = bs->CreateEvent ( EVT_TIMER, TPL_NOTIFY, NULL, NULL,
&tick ) ) != 0 ) { &tick ) ) != 0 ) {
@ -100,6 +103,9 @@ static void efi_entropy_disable ( void ) {
/* Close timer tick event */ /* Close timer tick event */
bs->CloseEvent ( tick ); bs->CloseEvent ( tick );
/* Return to TPL_CALLBACK */
bs->RaiseTPL ( TPL_CALLBACK );
} }
/** /**