1 files changed, 231 insertions, 0 deletions
diff --git a/roms/ipxe/src/arch/i386/firmware/pcbios/hidemem.c b/roms/ipxe/src/arch/i386/firmware/pcbios/hidemem.c
new file mode 100644
index 00000000..8f3069e1
--- /dev/null
+++ b/roms/ipxe/src/arch/i386/firmware/pcbios/hidemem.c
@@ -0,0 +1,231 @@
+/* Copyright (C) 2006 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.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <assert.h>
+#include <realmode.h>
+#include <biosint.h>
+#include <basemem.h>
+#include <fakee820.h>
+#include <ipxe/init.h>
+#include <ipxe/io.h>
+#include <ipxe/hidemem.h>
+
+/** Set to true if you want to test a fake E820 map */
+#define FAKE_E820 0
+
+/** Alignment for hidden memory regions */
+#define ALIGN_HIDDEN 4096   /* 4kB page alignment should be enough */
+
+/**
+ * A hidden region of iPXE
+ *
+ * This represents a region that will be edited out of the system's
+ * memory map.
+ *
+ * This structure is accessed by assembly code, so must not be
+ * changed.
+ */
+struct hidden_region {
+	/** Physical start address */
+	uint64_t start;
+	/** Physical end address */
+	uint64_t end;
+};
+
+/** Hidden base memory */
+extern struct hidden_region __data16 ( hidemem_base );
+#define hidemem_base __use_data16 ( hidemem_base )
+
+/** Hidden umalloc memory */
+extern struct hidden_region __data16 ( hidemem_umalloc );
+#define hidemem_umalloc __use_data16 ( hidemem_umalloc )
+
+/** Hidden text memory */
+extern struct hidden_region __data16 ( hidemem_textdata );
+#define hidemem_textdata __use_data16 ( hidemem_textdata )
+
+/** Assembly routine in e820mangler.S */
+extern void int15();
+
+/** Vector for storing original INT 15 handler */
+extern struct segoff __text16 ( int15_vector );
+#define int15_vector __use_text16 ( int15_vector )
+
+/* The linker defines these symbols for us */
+extern char _textdata[];
+extern char _etextdata[];
+extern char _text16_memsz[];
+#define _text16_memsz ( ( unsigned int ) _text16_memsz )
+extern char _data16_memsz[];
+#define _data16_memsz ( ( unsigned int ) _data16_memsz )
+
+/**
+ * Hide region of memory from system memory map
+ *
+ * @v region		Hidden memory region
+ * @v start		Start of region
+ * @v end		End of region
+ */
+static void hide_region ( struct hidden_region *region,
+			  physaddr_t start, physaddr_t end ) {
+
+	/* Some operating systems get a nasty shock if a region of the
+	 * E820 map seems to start on a non-page boundary.  Make life
+	 * safer by rounding out our edited region.
+	 */
+	region->start = ( start & ~( ALIGN_HIDDEN - 1 ) );
+	region->end = ( ( end + ALIGN_HIDDEN - 1 ) & ~( ALIGN_HIDDEN - 1 ) );
+
+	DBG ( "Hiding region [%llx,%llx)\n", region->start, region->end );
+}
+
+/**
+ * Hide used base memory
+ *
+ */
+void hide_basemem ( void ) {
+	/* Hide from the top of free base memory to 640kB.  Don't use
+	 * hide_region(), because we don't want this rounded to the
+	 * nearest page boundary.
+	 */
+	hidemem_base.start = ( get_fbms() * 1024 );
+}
+
+/**
+ * Hide umalloc() region
+ *
+ */
+void hide_umalloc ( physaddr_t start, physaddr_t end ) {
+	assert ( end <= virt_to_phys ( _textdata ) );
+	hide_region ( &hidemem_umalloc, start, end );
+}
+
+/**
+ * Hide .text and .data
+ *
+ */
+void hide_textdata ( void ) {
+	hide_region ( &hidemem_textdata, virt_to_phys ( _textdata ),
+		      virt_to_phys ( _etextdata ) );
+}
+
+/**
+ * Hide Etherboot
+ *
+ * Installs an INT 15 handler to edit Etherboot out of the memory map
+ * returned by the BIOS.
+ */
+static void hide_etherboot ( void ) {
+	struct memory_map memmap;
+	unsigned int rm_ds_top;
+	unsigned int rm_cs_top;
+	unsigned int fbms;
+
+	/* Dump memory map before mangling */
+	DBG ( "Hiding iPXE from system memory map\n" );
+	get_memmap ( &memmap );
+
+	/* Hook in fake E820 map, if we're testing one */
+	if ( FAKE_E820 ) {
+		DBG ( "Hooking in fake E820 map\n" );
+		fake_e820();
+		get_memmap ( &memmap );
+	}
+
+	/* Initialise the hidden regions */
+	hide_basemem();
+	hide_umalloc ( virt_to_phys ( _textdata ), virt_to_phys ( _textdata ) );
+	hide_textdata();
+
+	/* Some really moronic BIOSes bring up the PXE stack via the
+	 * UNDI loader entry point and then don't bother to unload it
+	 * before overwriting the code and data segments.  If this
+	 * happens, we really don't want to leave INT 15 hooked,
+	 * because that will cause any loaded OS to die horribly as
+	 * soon as it attempts to fetch the system memory map.
+	 *
+	 * We use a heuristic to guess whether or not we are being
+	 * loaded sensibly.
+	 */
+	rm_cs_top = ( ( ( rm_cs << 4 ) + _text16_memsz + 1024 - 1 ) >> 10 );
+	rm_ds_top = ( ( ( rm_ds << 4 ) + _data16_memsz + 1024 - 1 ) >> 10 );
+	fbms = get_fbms();
+	if ( ( rm_cs_top < fbms ) && ( rm_ds_top < fbms ) ) {
+		DBG ( "Detected potentially unsafe UNDI load at CS=%04x "
+		      "DS=%04x FBMS=%dkB\n", rm_cs, rm_ds, fbms );
+		DBG ( "Disabling INT 15 memory hiding\n" );
+		return;
+	}
+
+	/* Hook INT 15 */
+	hook_bios_interrupt ( 0x15, ( unsigned int ) int15,
+			      &int15_vector );
+
+	/* Dump memory map after mangling */
+	DBG ( "Hidden iPXE from system memory map\n" );
+	get_memmap ( &memmap );
+}
+
+/**
+ * Unhide Etherboot
+ *
+ * Uninstalls the INT 15 handler installed by hide_etherboot(), if
+ * possible.
+ */
+static void unhide_etherboot ( int flags __unused ) {
+	struct memory_map memmap;
+	int rc;
+
+	/* If we have more than one hooked interrupt at this point, it
+	 * means that some other vector is still hooked, in which case
+	 * we can't safely unhook INT 15 because we need to keep our
+	 * memory protected.  (We expect there to be at least one
+	 * hooked interrupt, because INT 15 itself is still hooked).
+	 */
+	if ( hooked_bios_interrupts > 1 ) {
+		DBG ( "Cannot unhide: %d interrupt vectors still hooked\n",
+		      hooked_bios_interrupts );
+		return;
+	}
+
+	/* Try to unhook INT 15 */
+	if ( ( rc = unhook_bios_interrupt ( 0x15, ( unsigned int ) int15,
+					    &int15_vector ) ) != 0 ) {
+		DBG ( "Cannot unhook INT15: %s\n", strerror ( rc ) );
+		/* Leave it hooked; there's nothing else we can do,
+		 * and it should be intrinsically safe (though
+		 * wasteful of RAM).
+		 */
+	}
+
+	/* Unhook fake E820 map, if used */
+	if ( FAKE_E820 )
+		unfake_e820();
+
+	/* Dump memory map after unhiding */
+	DBG ( "Unhidden iPXE from system memory map\n" );
+	get_memmap ( &memmap );
+}
+
+/** Hide Etherboot startup function */
+struct startup_fn hide_etherboot_startup_fn __startup_fn ( STARTUP_EARLY ) = {
+	.startup = hide_etherboot,
+	.shutdown = unhide_etherboot,
+};