x86emu: Add an RDTSC implementation to the x86 emulator

This instruction is being used in some debug VBIOSes.  This implementation
doesn't even try to be accurate.  Instead, it just increments the counter by a
fixed amount every time an rdtsc instruction in encountered, to avoid divides
by zero.

Imported from:

Change-Id: I8fba1a060c57ccb7bbd44aa321dd349bc56bf574
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/1362
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
1 file changed