setup, acpi: map BIOS areas where ACPI's RSDP table is located

This is needed to get rid of "Low memory" mappings. Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
KernelTestFramework · Jul 30, 2021 · 015fb7a · 015fb7a
1 parent 4fb9742
commit 015fb7a
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Showing 3 changed files with 19 additions and 5 deletions.
diff --git a/common/acpi.c b/common/acpi.c
@@ -33,9 +33,6 @@
 #include <percpu.h>
 #include <string.h>
 
-#define ACPI_RSDP_BIOS_ROM_START 0xE0000
-#define ACPI_RSDP_BIOS_ROM_STOP  0xFFFFF
-
 acpi_table_t *acpi_tables[128];
 unsigned max_acpi_tables;
 
@@ -109,8 +106,8 @@ static rsdp_rev1_t *acpi_find_rsdp(void) {
     if (rsdp)
         return rsdp;
 
-    rsdp = find_rsdp(paddr_to_virt_kern(ACPI_RSDP_BIOS_ROM_START),
-                     paddr_to_virt_kern(ACPI_RSDP_BIOS_ROM_STOP));
+    rsdp = find_rsdp(paddr_to_virt_kern(BIOS_ACPI_ROM_START),
+                     paddr_to_virt_kern(BIOS_ACPI_ROM_STOP));
     if (rsdp)
         return rsdp;
 

diff --git a/common/setup.c b/common/setup.c
@@ -179,6 +179,19 @@ void zap_boot_mappings(void) {
     }
 }
 
+static void map_bios_area(void) {
+    vmap_4k(paddr_to_virt(BDA_ADDR_START), paddr_to_mfn(BDA_ADDR_START), L1_PROT_RO);
+    kmap_4k(paddr_to_mfn(BDA_ADDR_START), L1_PROT_RO);
+
+    uint32_t ebda_addr = get_bios_ebda_addr();
+    vmap_4k(paddr_to_virt(ebda_addr), paddr_to_mfn(ebda_addr), L1_PROT_RO);
+    kmap_4k(paddr_to_mfn(ebda_addr), L1_PROT_RO);
+
+    for (mfn_t bios_mfn = paddr_to_mfn(BIOS_ACPI_ROM_START);
+         bios_mfn < paddr_to_mfn(BIOS_ACPI_ROM_STOP); bios_mfn++)
+        kmap_4k(bios_mfn, L1_PROT_RO);
+}
+
 void __noreturn __text_init kernel_start(uint32_t multiboot_magic,
                                          multiboot_info_t *mbi) {
     /* Zero-out BSS sections */
@@ -220,6 +233,7 @@ void __noreturn __text_init kernel_start(uint32_t multiboot_magic,
     init_pagetables();
 
     map_multiboot_areas();
+    map_bios_area();
 
     write_cr3(cr3.paddr);
     WRITE_SP(get_free_pages_top(PAGE_ORDER_2M, GFP_KERNEL));

diff --git a/include/mm/pmm.h b/include/mm/pmm.h
@@ -31,6 +31,9 @@
 #define BDA_COM_PORTS_ENTRY 0x400
 #define EBDA_ADDR_ENTRY     0x40E
 
+#define BIOS_ACPI_ROM_START 0xE0000
+#define BIOS_ACPI_ROM_STOP  0xFFFFF
+
 #define BIOS_ROM_ADDR_START 0xF0000
 
 #ifndef __ASSEMBLY__