Kernel: Add convenient ways to map whole BIOS and EBDA into memory

This patch adds a MappedROM abstraction to the Kernel VM subsystem.
It's basically the read-only byte buffer equivalent of a TypedMapping.

We use this in the ACPI and MP table parsers to scan for interesting
stuff in low memory instead of doing a bunch of address arithmetic.

2 files changed, 95 insertions, 0 deletions

diff --git a/Kernel/Arch/PC/BIOS.cpp b/Kernel/Arch/PC/BIOS.cpp
new file mode 100644
index 0000000000..f8cae3855a
--- /dev/null
+++ b/Kernel/Arch/PC/BIOS.cpp
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/StringView.h>
+#include <Kernel/Arch/PC/BIOS.h>
+#include <Kernel/VM/MemoryManager.h>
+#include <Kernel/VM/TypedMapping.h>
+
+namespace Kernel {
+
+MappedROM map_bios()
+{
+    MappedROM mapping;
+    mapping.size = 128 * KB;
+    mapping.paddr = PhysicalAddress(0xe0000);
+    mapping.region = MM.allocate_kernel_region(mapping.paddr, PAGE_ROUND_UP(mapping.size), {}, Region::Access::Read);
+    return mapping;
+}
+
+MappedROM map_ebda()
+{
+    auto ebda_segment_ptr = map_typed<u16>(PhysicalAddress(0x40e));
+    auto ebda_length_ptr = map_typed<u16>(PhysicalAddress(0x413));
+
+    PhysicalAddress ebda_paddr(*ebda_segment_ptr << 4);
+    size_t ebda_size = *ebda_length_ptr;
+
+    MappedROM mapping;
+    mapping.region = MM.allocate_kernel_region(ebda_paddr.page_base(), PAGE_ROUND_UP(ebda_size), {}, Region::Access::Read);
+    mapping.offset = ebda_paddr.offset_in_page();
+    mapping.size = ebda_size;
+    mapping.paddr = ebda_paddr;
+    return mapping;
+}
+
+}
diff --git a/Kernel/Arch/PC/BIOS.h b/Kernel/Arch/PC/BIOS.h
new file mode 100644
index 0000000000..642e221d14
--- /dev/null
+++ b/Kernel/Arch/PC/BIOS.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <Kernel/VM/MappedROM.h>
+
+namespace Kernel {
+
+MappedROM map_bios();
+MappedROM map_ebda();
+
+}