1 files changed, 136 insertions, 0 deletions
diff --git a/kernel/arch/x86/boot/memory.c b/kernel/arch/x86/boot/memory.c
new file mode 100644
index 000000000..db75d07c3
--- /dev/null
+++ b/kernel/arch/x86/boot/memory.c
@@ -0,0 +1,136 @@
+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright (C) 1991, 1992 Linus Torvalds
+ *   Copyright 2007 rPath, Inc. - All Rights Reserved
+ *   Copyright 2009 Intel Corporation; author H. Peter Anvin
+ *
+ *   This file is part of the Linux kernel, and is made available under
+ *   the terms of the GNU General Public License version 2.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * Memory detection code
+ */
+
+#include "boot.h"
+
+#define SMAP	0x534d4150	/* ASCII "SMAP" */
+
+static int detect_memory_e820(void)
+{
+	int count = 0;
+	struct biosregs ireg, oreg;
+	struct e820entry *desc = boot_params.e820_map;
+	static struct e820entry buf; /* static so it is zeroed */
+
+	initregs(&ireg);
+	ireg.ax  = 0xe820;
+	ireg.cx  = sizeof buf;
+	ireg.edx = SMAP;
+	ireg.di  = (size_t)&buf;
+
+	/*
+	 * Note: at least one BIOS is known which assumes that the
+	 * buffer pointed to by one e820 call is the same one as
+	 * the previous call, and only changes modified fields.  Therefore,
+	 * we use a temporary buffer and copy the results entry by entry.
+	 *
+	 * This routine deliberately does not try to account for
+	 * ACPI 3+ extended attributes.  This is because there are
+	 * BIOSes in the field which report zero for the valid bit for
+	 * all ranges, and we don't currently make any use of the
+	 * other attribute bits.  Revisit this if we see the extended
+	 * attribute bits deployed in a meaningful way in the future.
+	 */
+
+	do {
+		intcall(0x15, &ireg, &oreg);
+		ireg.ebx = oreg.ebx; /* for next iteration... */
+
+		/* BIOSes which terminate the chain with CF = 1 as opposed
+		   to %ebx = 0 don't always report the SMAP signature on
+		   the final, failing, probe. */
+		if (oreg.eflags & X86_EFLAGS_CF)
+			break;
+
+		/* Some BIOSes stop returning SMAP in the middle of
+		   the search loop.  We don't know exactly how the BIOS
+		   screwed up the map at that point, we might have a
+		   partial map, the full map, or complete garbage, so
+		   just return failure. */
+		if (oreg.eax != SMAP) {
+			count = 0;
+			break;
+		}
+
+		*desc++ = buf;
+		count++;
+	} while (ireg.ebx && count < ARRAY_SIZE(boot_params.e820_map));
+
+	return boot_params.e820_entries = count;
+}
+
+static int detect_memory_e801(void)
+{
+	struct biosregs ireg, oreg;
+
+	initregs(&ireg);
+	ireg.ax = 0xe801;
+	intcall(0x15, &ireg, &oreg);
+
+	if (oreg.eflags & X86_EFLAGS_CF)
+		return -1;
+
+	/* Do we really need to do this? */
+	if (oreg.cx || oreg.dx) {
+		oreg.ax = oreg.cx;
+		oreg.bx = oreg.dx;
+	}
+
+	if (oreg.ax > 15*1024) {
+		return -1;	/* Bogus! */
+	} else if (oreg.ax == 15*1024) {
+		boot_params.alt_mem_k = (oreg.bx << 6) + oreg.ax;
+	} else {
+		/*
+		 * This ignores memory above 16MB if we have a memory
+		 * hole there.  If someone actually finds a machine
+		 * with a memory hole at 16MB and no support for
+		 * 0E820h they should probably generate a fake e820
+		 * map.
+		 */
+		boot_params.alt_mem_k = oreg.ax;
+	}
+
+	return 0;
+}
+
+static int detect_memory_88(void)
+{
+	struct biosregs ireg, oreg;
+
+	initregs(&ireg);
+	ireg.ah = 0x88;
+	intcall(0x15, &ireg, &oreg);
+
+	boot_params.screen_info.ext_mem_k = oreg.ax;
+
+	return -(oreg.eflags & X86_EFLAGS_CF); /* 0 or -1 */
+}
+
+int detect_memory(void)
+{
+	int err = -1;
+
+	if (detect_memory_e820() > 0)
+		err = 0;
+
+	if (!detect_memory_e801())
+		err = 0;
+
+	if (!detect_memory_88())
+		err = 0;
+
+	return err;
+}