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authorAngel Pons <th3fanbus@gmail.com>2020-10-20 23:03:45 +0200
committerAngel Pons <th3fanbus@gmail.com>2020-10-22 20:06:54 +0000
commit8f8cb95fe92170220ccf7ad44f22073fee561c40 (patch)
treea237f4f1aa620af8837ce1095004b965321b0417 /toolchain.inc
parent01490258bb26a1bbb7b41e0cf8100ec4d42082cb (diff)
sec/intel/txt: Split MTRR setup ASM code into a macro
If necessary, SCLEAN needs to run in early romstage, where DRAM is not working yet. In fact, that the DRAM isn't working is the reason to run SCLEAN in the first place. Before running GETSEC, CAR needs to be torn down, as MTRRs have to be reprogrammed to cache the BIOS ACM. Further, running SCLEAN leaves the system in an undefined state, where the only sane thing to do is reset the platform. Thus, invoking SCLEAN requires specific assembly prologue and epilogue sections before and after MTRR setup, and neither DRAM nor CAR may be relied upon for the MTRR setup. In order to handle this without duplicating the MTRR setup code, place it in a macro on a separate file. This needs to be a macro because the call and return instructions rely on the stack being usable, and it is not the case for SCLEAN. The MTRR code clobbers many registers, but no other choice remains when the registers cannot be saved anywhere else. Tested on Asrock B85M Pro4, BIOS ACM can still be launched. Change-Id: I2f5e82f57b458ca1637790ddc1ddc14bba68ac49 Signed-off-by: Angel Pons <th3fanbus@gmail.com> Reviewed-on: https://review.coreboot.org/c/coreboot/+/46603 Reviewed-by: Arthur Heymans <arthur@aheymans.xyz> Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
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