1 files changed, 125 insertions, 0 deletions
diff --git a/src/arch/x86/interface/pcbios/rsdp.c b/src/arch/x86/interface/pcbios/rsdp.c
new file mode 100644
index 00000000..8da0b558
--- /dev/null
+++ b/src/arch/x86/interface/pcbios/rsdp.c
@@ -0,0 +1,125 @@
+/*
+ * Copyright (C) 2017 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/**
+ * @file
+ *
+ * ACPI Root System Description Pointer
+ *
+ */
+
+#include <stdint.h>
+#include <realmode.h>
+#include <bios.h>
+#include <ipxe/acpi.h>
+#include <ipxe/rsdp.h>
+
+/** EBDA RSDP maximum segment */
+#define RSDP_EBDA_END_SEG 0xa000
+
+/** Fixed BIOS area RSDP start address */
+#define RSDP_BIOS_START 0xe0000
+
+/** Fixed BIOS area RSDP length */
+#define RSDP_BIOS_LEN 0x20000
+
+/** Stride at which to search for RSDP */
+#define RSDP_STRIDE 16
+
+/**
+ * Locate ACPI root system description table within a memory range
+ *
+ * @v start		Start address to search
+ * @v len		Length to search
+ * @ret rsdt		ACPI root system description table, or UNULL
+ */
+static userptr_t rsdp_find_rsdt_range ( userptr_t start, size_t len ) {
+	static const char signature[8] = RSDP_SIGNATURE;
+	struct acpi_rsdp rsdp;
+	userptr_t rsdt;
+	size_t offset;
+	uint8_t sum;
+	unsigned int i;
+
+	/* Search for RSDP */
+	for ( offset = 0 ; ( ( offset + sizeof ( rsdp ) ) < len ) ;
+	      offset += RSDP_STRIDE ) {
+
+		/* Check signature and checksum */
+		copy_from_user ( &rsdp, start, offset, sizeof ( rsdp ) );
+		if ( memcmp ( rsdp.signature, signature,
+			      sizeof ( signature ) ) != 0 )
+			continue;
+		for ( sum = 0, i = 0 ; i < sizeof ( rsdp ) ; i++ )
+			sum += *( ( ( uint8_t * ) &rsdp ) + i );
+		if ( sum != 0 )
+			continue;
+
+		/* Extract RSDT */
+		rsdt = phys_to_user ( le32_to_cpu ( rsdp.rsdt ) );
+		DBGC ( rsdt, "RSDT %#08lx found via RSDP %#08lx\n",
+		       user_to_phys ( rsdt, 0 ),
+		       user_to_phys ( start, offset ) );
+		return rsdt;
+	}
+
+	return UNULL;
+}
+
+/**
+ * Locate ACPI root system description table
+ *
+ * @ret rsdt		ACPI root system description table, or UNULL
+ */
+static userptr_t rsdp_find_rsdt ( void ) {
+	static userptr_t rsdt;
+	uint16_t ebda_seg;
+	userptr_t ebda;
+	size_t ebda_len;
+
+	/* Return existing RSDT if already found */
+	if ( rsdt )
+		return rsdt;
+
+	/* Search EBDA */
+	get_real ( ebda_seg, BDA_SEG, BDA_EBDA );
+	if ( ebda_seg < RSDP_EBDA_END_SEG ) {
+	     ebda = real_to_user ( ebda_seg, 0 );
+	     ebda_len = ( ( RSDP_EBDA_END_SEG - ebda_seg ) * 16 );
+	     rsdt = rsdp_find_rsdt_range ( ebda, ebda_len );
+	     if ( rsdt )
+		     return rsdt;
+	}
+
+	/* Search fixed BIOS area */
+	rsdt = rsdp_find_rsdt_range ( phys_to_user ( RSDP_BIOS_START ),
+				      RSDP_BIOS_LEN );
+	if ( rsdt )
+		return rsdt;
+
+	return UNULL;
+}
+
+PROVIDE_ACPI ( rsdp, acpi_find_rsdt, rsdp_find_rsdt );