cpu/x86/64bit: Generate static page tables from an assembly file
This removes the need for a tool to generate simple identity pages.
Future patches will link this page table directly into the stages on
some platforms so having an assembly file makes a lot of sense.
This also optimizes the size of the page of each 4K page by placing
the PDPE_table below the PDE.
Change-Id: Ia1e31b701a2584268c85d327bf139953213899e3
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63725
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
diff --git a/src/cpu/x86/64bit/Makefile.inc b/src/cpu/x86/64bit/Makefile.inc
index 721e620..1895498 100644
--- a/src/cpu/x86/64bit/Makefile.inc
+++ b/src/cpu/x86/64bit/Makefile.inc
@@ -5,3 +5,15 @@
romstage-y += mode_switch.S
postcar-y += mode_switch.S
ramstage-y += mode_switch.S
+
+# Add --defsym=_start=0 to suppress a linker warning.
+$(objcbfs)/pt: $(dir)/pt.S
+ $(CC_bootblock) $(CFLAGS_bootblock) $(CPPFLAGS_bootblock) -o $@.tmp $< -Wl,--section-start=.rodata=$(CONFIG_ARCH_X86_64_PGTBL_LOC),--defsym=_start=0
+ $(OBJCOPY_ramstage) -Obinary -j .rodata $@.tmp $@
+ rm $@.tmp
+
+cbfs-files-y += pagetables
+pagetables-file := $(objcbfs)/pt
+pagetables-type := raw
+pagetables-compression := none
+pagetables-COREBOOT-position := $(CONFIG_ARCH_X86_64_PGTBL_LOC)
diff --git a/src/cpu/x86/64bit/pt.S b/src/cpu/x86/64bit/pt.S
new file mode 100644
index 0000000..b105528
--- /dev/null
+++ b/src/cpu/x86/64bit/pt.S
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+/*
+ * For reference see "AMD64 Architecture Programmer's Manual Volume 2",
+ * Document 24593-Rev. 3.31-July 2019 Chapter 5.3.4
+ *
+ * Page table attributes: WB, User+Supervisor, Present, Writeable, Accessed, Dirty
+ */
+
+.section .rodata
+#define _PRES (1ULL << 0)
+#define _RW (1ULL << 1)
+#define _US (1ULL << 2)
+#define _A (1ULL << 5)
+#define _D (1ULL << 6)
+#define _PS (1ULL << 7)
+#define _GEN_DIR(a) (_PRES + _RW + _US + _A + (a))
+#define _GEN_PAGE(a) (_PRES + _RW + _US + _PS + _A + _D + (a))
+
+.global PM4LE
+.align 32
+PM4LE:
+.quad _GEN_DIR(PDPE_table)
+
+.align 4096
+PDE_tables: /* identity map 2MiB pages */
+.rept 2048
+.quad _GEN_PAGE(0x200000 * ((. - PDE_tables) >> 3))
+.endr
+
+.align 4096
+PDPE_table: /* Point to PDE */
+.rept 4
+.quad _GEN_DIR(PDE_tables + 4096 * ((. - PDPE_table) >> 3))
+.endr