From 2c0d74e8e8303a902498ed62762d4fb008f0c008 Mon Sep 17 00:00:00 2001
From: Nate Lawson <njl@FreeBSD.org>
Date: Tue, 25 May 2004 05:52:48 +0000
Subject: [PATCH] Use the correct location of the EBDA for searching for the
 RSDP. The EBDA is the 1 KB area addressed by the 16 bit pointer at 0x40E.

Pointed out by:	robert.moore AT intel.com
---
 sys/boot/i386/libi386/biosacpi.c   | 16 ++++++-----
 usr.sbin/acpi/acpidump/acpi_user.c | 46 +++++++++++++++++++-----------
 usr.sbin/acpi/acpidump/acpidump.h  |  4 +--
 3 files changed, 40 insertions(+), 26 deletions(-)

diff --git a/sys/boot/i386/libi386/biosacpi.c b/sys/boot/i386/libi386/biosacpi.c
index c8ee1c7c46d1..f9b2d774b054 100644
--- a/sys/boot/i386/libi386/biosacpi.c
+++ b/sys/boot/i386/libi386/biosacpi.c
@@ -84,22 +84,24 @@ biosacpi_detect(void)
 }
 
 /*
- * Find the RSDP in low memory.
+ * Find the RSDP in low memory.  See section 5.2.2 of the ACPI spec.
  */
 static RSDP_DESCRIPTOR *
 biosacpi_find_rsdp(void)
 {
     RSDP_DESCRIPTOR	*rsdp;
+    uint16_t		*addr;
 
-    /* search the EBDA */
-    if ((rsdp = biosacpi_search_rsdp((char *)0, 0x400)) != NULL)
-	return(rsdp);
+    /* EBDA is the 1 KB addressed by the 16 bit pointer at 0x40E. */
+    addr = (uint16_t *)0x40E;
+    if ((rsdp = biosacpi_search_rsdp((char *)(*addr << 4), 0x400)) != NULL)
+	return (rsdp);
 
-    /* search the BIOS space */
+    /* Check the upper memory BIOS space, 0xe0000 - 0xfffff. */
     if ((rsdp = biosacpi_search_rsdp((char *)0xe0000, 0x20000)) != NULL)
-	return(rsdp);
+	return (rsdp);
 
-    return(NULL);
+    return (NULL);
 }
 
 static RSDP_DESCRIPTOR *
diff --git a/usr.sbin/acpi/acpidump/acpi_user.c b/usr.sbin/acpi/acpidump/acpi_user.c
index 7bb2d0af0b63..2166e884c800 100644
--- a/usr.sbin/acpi/acpidump/acpi_user.c
+++ b/usr.sbin/acpi/acpidump/acpi_user.c
@@ -121,6 +121,34 @@ acpi_get_rsdp(u_long addr)
 	return (acpi_map_physical(addr, len));
 }
 
+static struct ACPIrsdp *
+acpi_scan_rsd_ptr(void)
+{
+#if defined(__i386__)
+	struct ACPIrsdp *rsdp;
+	u_long		addr, end;
+
+	/*
+	 * On ia32, scan physical memory for the RSD PTR if above failed.
+	 * According to section 5.2.2 of the ACPI spec, we only consider
+	 * two regions for the base address:
+	 * 1. EBDA (1 KB area addressed by the 16 bit pointer at 0x40E
+	 * 2. High memory (0xE0000 - 0xFFFFF)
+	 */
+	addr = RSDP_EBDA_PTR;
+	pread(acpi_mem_fd, &addr, sizeof(uint16_t), addr);
+	addr <<= 4;
+	end = addr + RSDP_EBDA_SIZE;
+	for (; addr < end; addr += 16)
+		if ((rsdp = acpi_get_rsdp(addr)) != NULL)
+			return (rsdp);
+	for (addr = RSDP_HI_START; addr < RSDP_HI_END; addr += 16)
+		if ((rsdp = acpi_get_rsdp(addr)) != NULL)
+			return (rsdp);
+#endif /* __i386__ */
+	return (NULL);
+}
+
 /*
  * Public interfaces
  */
@@ -143,23 +171,7 @@ acpi_find_rsd_ptr(void)
 			    machdep_acpi_root);
 	}
 
-#if defined(__i386__)
-	/*
-	 * On ia32, scan physical memory for the RSD PTR if above failed.
-	 * According to section 5.2.2 of the ACPI spec, we only consider
-	 * two regions for the base address:
-	 * 1. EBDA (0x0 - 0x3FF)
-	 * 2. High memory (0xE0000 - 0xFFFFF)
-	 */
-	for (addr = RSDP_EBDA_START; addr < RSDP_EBDA_END; addr += 16)
-		if ((rsdp = acpi_get_rsdp(addr)) != NULL)
-			return (rsdp);
-	for (addr = RSDP_HI_START; addr < RSDP_HI_END; addr += 16)
-		if ((rsdp = acpi_get_rsdp(addr)) != NULL)
-			return (rsdp);
-#endif
-
-	return (NULL);
+	return (acpi_scan_rsd_ptr());
 }
 
 void *
diff --git a/usr.sbin/acpi/acpidump/acpidump.h b/usr.sbin/acpi/acpidump/acpidump.h
index e3256181cd53..6cd7a8e7b18a 100644
--- a/usr.sbin/acpi/acpidump/acpidump.h
+++ b/usr.sbin/acpi/acpidump/acpidump.h
@@ -299,8 +299,8 @@ struct ECDTbody {
  * 1. EBDA (0x0 - 0x3FF)
  * 2. High memory (0xE0000 - 0xFFFFF)
  */
-#define RSDP_EBDA_START	0
-#define RSDP_EBDA_END	(0x400 - sizeof(struct ACPIrsdp))
+#define RSDP_EBDA_PTR	0x40E
+#define RSDP_EBDA_SIZE	(1024 - sizeof(struct ACPIrsdp))
 #define RSDP_HI_START	0xE0000
 #define RSDP_HI_END	(0x100000 - sizeof(struct ACPIrsdp))