# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1233684663 0
# Node ID aca402831ac1eb8086e58370d51360a72c39e39b
# Parent d68178692b7ce1c8dc02fc78f1c131ecf8f410a7
x86: Relocate Multiboot structures where we know they will be
accessible. GRUB2 seems to like to stick them really high sometimes
(just below 4GB).
The 32-bit C code framework that this sets up can also be used for
other stuff in future:
* early cmdline parsing
* relocating multiboot modules so they too are guaranteed accessible
Its interaction with normal Xen start-of-day, and with the 16-bit
assembly trampoline, needs a bit of thought.
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
.hgignore | 10 -----
xen/arch/x86/Makefile | 1
xen/arch/x86/boot/Makefile | 6 +++
xen/arch/x86/boot/build32.mk | 24 ++++++++++++
xen/arch/x86/boot/head.S | 10 ++++-
xen/arch/x86/boot/reloc.c | 80 +++++++++++++++++++++++++++++++++++++++++++
6 files changed, 120 insertions(+), 11 deletions(-)
diff -r d68178692b7c -r aca402831ac1 .hgignore
--- a/.hgignore Tue Feb 03 14:06:51 2009 +0000
+++ b/.hgignore Tue Feb 03 18:11:03 2009 +0000
@@ -256,6 +256,7 @@
^xen/arch/x86/asm-offsets\.s$
^xen/arch/x86/boot/mkelf32$
^xen/arch/x86/xen\.lds$
+^xen/arch/x86/boot/reloc.S$
^xen/ddb/.*$
^xen/include/asm$
^xen/include/asm-.*/asm-offsets\.h$
@@ -279,15 +280,6 @@
^xen/arch/ia64/asm-xsi-offsets\.s$
^xen/arch/ia64/map\.out$
^xen/arch/ia64/xen\.lds\.s$
-^xen/arch/powerpc/dom0\.bin$
-^xen/arch/powerpc/asm-offsets\.s$
-^xen/arch/powerpc/firmware$
-^xen/arch/powerpc/firmware.dbg$
-^xen/arch/powerpc/firmware_image.bin$
-^xen/arch/powerpc/xen\.lds$
-^xen/arch/powerpc/\.xen-syms$
-^xen/arch/powerpc/xen-syms\.S$
-^xen/arch/powerpc/cmdline.dep$
^unmodified_drivers/linux-2.6/\.tmp_versions
^unmodified_drivers/linux-2.6/.*\.cmd$
^unmodified_drivers/linux-2.6/.*\.ko$
diff -r d68178692b7c -r aca402831ac1 xen/arch/x86/Makefile
--- a/xen/arch/x86/Makefile Tue Feb 03 14:06:51 2009 +0000
+++ b/xen/arch/x86/Makefile Tue Feb 03 18:11:03 2009 +0000
@@ -92,3 +92,4 @@ clean::
clean::
rm -f asm-offsets.s xen.lds boot/*.o boot/*~ boot/core boot/mkelf32
rm -f $(BASEDIR)/.xen-syms.[0-9]* boot/.*.d
+ rm -f boot/reloc.S boot/reloc.lnk boot/reloc.bin
diff -r d68178692b7c -r aca402831ac1 xen/arch/x86/boot/Makefile
--- a/xen/arch/x86/boot/Makefile Tue Feb 03 14:06:51 2009 +0000
+++ b/xen/arch/x86/boot/Makefile Tue Feb 03 18:11:03 2009 +0000
@@ -1,1 +1,7 @@ obj-y += head.o
obj-y += head.o
+
+head.o: reloc.S
+
+# NB. BOOT_TRAMPOLINE == 0x8c000
+%.S: %.c
+ RELOC=0x8c000 $(MAKE) -f build32.mk $@
diff -r d68178692b7c -r aca402831ac1 xen/arch/x86/boot/build32.mk
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/xen/arch/x86/boot/build32.mk Tue Feb 03 18:11:03 2009 +0000
@@ -0,0 +1,24 @@
+XEN_ROOT=../../../..
+override XEN_TARGET_ARCH=x86_32
+CFLAGS =
+include $(XEN_ROOT)/Config.mk
+
+# Disable PIE/SSP if GCC supports them. They can break us.
+$(call cc-option-add,CFLAGS,CC,-nopie)
+$(call cc-option-add,CFLAGS,CC,-fno-stack-protector)
+$(call cc-option-add,CFLAGS,CC,-fno-stack-protector-all)
+
+CFLAGS += -Werror -fno-builtin -msoft-float
+
+%.S: %.bin
+ (od -v -t x $< | head -n -1 | \
+ sed 's/ /,0x/g' | sed 's/^[0-9]*,/ .long /') >$@
+
+%.bin: %.lnk
+ $(OBJCOPY) -O binary $< $@
+
+%.lnk: %.o
+ $(LD) $(LDFLAGS_DIRECT) -N -Ttext 0x8c000 -o $@ $<
+
+%.o: %.c
+ $(CC) $(CFLAGS) -c $< -o $@
diff -r d68178692b7c -r aca402831ac1 xen/arch/x86/boot/head.S
--- a/xen/arch/x86/boot/head.S Tue Feb 03 14:06:51 2009 +0000
+++ b/xen/arch/x86/boot/head.S Tue Feb 03 18:11:03 2009 +0000
@@ -79,8 +79,11 @@ __start:
cmp $0x2BADB002,%eax
jne not_multiboot
- /* Save the Multiboot info structure for later use. */
- mov %ebx,sym_phys(multiboot_ptr)
+ /* Save the Multiboot info struct (after relocation) for later use. */
+ mov $sym_phys(cpu0_stack)+1024,%esp
+ push %ebx
+ call reloc
+ mov %eax,sym_phys(multiboot_ptr)
/* Initialize BSS (no nasty surprises!) */
mov $sym_phys(__bss_start),%edi
@@ -192,6 +195,9 @@ 2: cmp $L1_PAGETABLE_ENTRIES,%e
#include "cmdline.S"
+reloc:
+#include "reloc.S"
+
.align 16
.globl trampoline_start, trampoline_end
trampoline_start:
diff -r d68178692b7c -r aca402831ac1 xen/arch/x86/boot/reloc.c
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/xen/arch/x86/boot/reloc.c Tue Feb 03 18:11:03 2009 +0000
@@ -0,0 +1,80 @@
+/******************************************************************************
+ * reloc.c
+ *
+ * 32-bit flat memory-map routines for relocating Multiboot structures
+ * and modules. This is most easily done early with paging disabled.
+ *
+ * Copyright (c) 2009, Citrix Systems, Inc.
+ *
+ * Authors:
+ * Keir Fraser <keir.fraser@xxxxxxxxxx>
+ */
+
+asm (
+ " .text \n"
+ " .globl _start \n"
+ "_start: \n"
+ " mov $_start,%edi \n"
+ " call 1f \n"
+ "1: pop %esi \n"
+ " sub $1b-_start,%esi \n"
+ " mov $__bss_start-_start,%ecx \n"
+ " rep movsb \n"
+ " xor %eax,%eax \n"
+ " mov $_end,%ecx \n"
+ " sub %edi,%ecx \n"
+ " rep stosb \n"
+ " mov $reloc,%eax \n"
+ " jmp *%eax \n"
+ );
+
+typedef unsigned int u32;
+#include "../../../include/xen/multiboot.h"
+
+extern char _start[];
+
+static void *memcpy(void *dest, const void *src, unsigned int n)
+{
+ char *s = (char *)src, *d = dest;
+ while ( n-- )
+ *d++ = *s++;
+ return dest;
+}
+
+static void *reloc_mbi_struct(void *old, unsigned int bytes)
+{
+ static void *alloc = &_start;
+ alloc = (void *)(((unsigned long)alloc - bytes) & ~15ul);
+ return memcpy(alloc, old, bytes);
+}
+
+multiboot_info_t *reloc(multiboot_info_t *mbi_old)
+{
+ multiboot_info_t *mbi = reloc_mbi_struct(mbi_old, sizeof(*mbi));
+
+ if ( mbi->flags & MBI_CMDLINE )
+ {
+ char *cmdline_old, *p;
+ cmdline_old = (char *)mbi->cmdline;
+ for ( p = cmdline_old; *p != '\0'; p++ )
+ continue;
+ mbi->cmdline = (u32)reloc_mbi_struct(cmdline_old, p - cmdline_old + 1);
+ }
+
+ if ( mbi->flags & MBI_MODULES )
+ mbi->mods_addr = (u32)reloc_mbi_struct(
+ (module_t *)mbi->mods_addr, mbi->mods_count * sizeof(module_t));
+
+ if ( mbi->flags & MBI_MEMMAP )
+ mbi->mmap_addr = (u32)reloc_mbi_struct(
+ (memory_map_t *)mbi->mmap_addr, mbi->mmap_length);
+
+ /* Mask features we don't understand or don't relocate. */
+ mbi->flags &= (MBI_MEMLIMITS |
+ MBI_DRIVES |
+ MBI_CMDLINE |
+ MBI_MODULES |
+ MBI_MEMMAP);
+
+ return mbi;
+}
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