util/x86: add page page table generator

Certain platforms need paging enabled during cache-as-ram because
dirty lines are being evicted by a heavy speculative frontend. Paging
needs to be enabled in order to utilize the NX (no execute) bit for
the regions that are strictly data (such as the stack). This utility
creates 32-bit PAE page tables using a static address space, and
the resulting tables have entries for all the PDPTEs such that it makes
it easy to enable 2MiB naturally aligned DRAM mappings once memory is
trained. Either binary files can be generated or C files. The pages that
are linked use a default base address of 0xaa000000 that can be changed at
runtime to reflect where the page tables are actually loaded. Or
specify a physical address on the command line that is known a priori.

iomap.txt:
0xd0000000, 0x100000000, UC, NX # All of MMIO
0xff000000, 0x100000000, WP, # memory-mapped SPI
0xffff8000, 0x100000000, WP, # XIP bootblock
0xfef00000, 0xfefc0000, WB, NX # CAR
0xfef40000, 0xfefc0000, WB, # verstage
0xfef20000, 0xfefc0000, WB, # romstage
0xfef40000, 0xfefc0000, WB, # fsp-m

$ go run util/x86/x86_page_tables.go --iomap_file=iomap.txt
Merged address space:
00000000d0000000 -- 00000000fef00000 UC NX : 375 big 256 small
00000000fef00000 -- 00000000fef20000 WB NX : 0 big 32 small
00000000fef20000 -- 00000000fefc0000 WB    : 0 big 160 small
00000000fefc0000 -- 00000000ff000000 UC NX : 0 big 64 small
00000000ff000000 -- 0000000100000000 WP    : 8 big 0 small

Total Pages of page tables: 5

Pages linked using base address of 0xaa000000.

BUG=b:72728953

Change-Id: I47625a24979b196011e2293712a8cdbdbb880d79
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/24919
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
1 file changed