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-rw-r--r--kernel/arch/x86/boot/memory.c136
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;
+}