[Xen-devel] [PATCH v2 23/23] x86: add multiboot2 protocol support for relocatable images

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

Add multiboot2 protocol support for relocatable images. Only GRUB2
with relevant patches understands that feature. Older multiboot
protocol (regardless of version) compatible loaders ignore it
and everything works as usual.

Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
---
 xen/arch/x86/boot/head.S          |   46 +++++++++++++++++++++++++++++--------
 xen/arch/x86/x86_64/asm-offsets.c |    1 +
 xen/include/xen/multiboot2.h      |   13 +++++++++++
 3 files changed, 50 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index d484f68..2520e48 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -81,6 +81,13 @@ multiboot1_header_end:
         /* Align modules at page boundry. */
         mb2ht_init MB2_HT(MODULE_ALIGN), MB2_HT(REQUIRED)
 
+        /* Load address preference. */
+        mb2ht_init MB2_HT(RELOCATABLE), MB2_HT(OPTIONAL), \
+                   sym_phys(start), /* Min load address. */ \
+                   0xffffffff, /* Max load address (4 GiB - 1). */ \
+                   0x200000, /* Load address alignment (2 MiB). */ \
+                   MULTIBOOT2_LOAD_PREFERENCE_HIGH
+
         /* Console flags tag. */
         mb2ht_init MB2_HT(CONSOLE_FLAGS), MB2_HT(OPTIONAL), \
                    MULTIBOOT2_CONSOLE_FLAGS_EGA_TEXT_SUPPORTED
@@ -176,30 +183,39 @@ efi_multiboot2_proto:
         lea     MB2_fixed_sizeof(%rbx),%rcx
 
 0:
+        /* Get Xen image base address from Multiboot2 information. */
+        cmpl    $MULTIBOOT2_TAG_TYPE_BASE_ADDR,MB2_tag_type(%rcx)
+        jne     1f
+
+        mov     MB2_base_addr(%rcx),%ebp
+        sub     $XEN_IMG_OFFSET,%rbp
+        jmp     4f
+
+1:
         /* Get EFI SystemTable address from Multiboot2 information. */
         cmpl    $MULTIBOOT2_TAG_TYPE_EFI64,MB2_tag_type(%rcx)
-        jne     1f
+        jne     2f
 
         mov     MB2_efi64_st(%rcx),%rsi
 
         /* Do not go into real mode on EFI platform. */
         movb    $1,skip_realmode(%rip)
-        jmp     3f
+        jmp     4f
 
-1:
+2:
         /* Get EFI ImageHandle address from Multiboot2 information. */
         cmpl    $MULTIBOOT2_TAG_TYPE_EFI64_IH,MB2_tag_type(%rcx)
-        jne     2f
+        jne     3f
 
         mov     MB2_efi64_ih(%rcx),%rdi
-        jmp     3f
+        jmp     4f
 
-2:
+3:
         /* Is it the end of Multiboot2 information? */
         cmpl    $MULTIBOOT2_TAG_TYPE_END,MB2_tag_type(%rcx)
         je      run_bs
 
-3:
+4:
         /* Go to next Multiboot2 information tag. */
         add     MB2_tag_size(%rcx),%ecx
         add     $(MULTIBOOT2_TAG_ALIGN-1),%rcx
@@ -297,14 +313,23 @@ multiboot2_proto:
         lea     MB2_fixed_sizeof(%ebx),%ecx
 
 0:
+        /* Get Xen image base address from Multiboot2 information. */
+        cmpl    $MULTIBOOT2_TAG_TYPE_BASE_ADDR,MB2_tag_type(%ecx)
+        jne     1f
+
+        mov     MB2_base_addr(%ecx),%ebp
+        sub     $XEN_IMG_OFFSET,%ebp
+        jmp     3f
+
+1:
         /* Get mem_lower from Multiboot2 information. */
         cmpl    $MULTIBOOT2_TAG_TYPE_BASIC_MEMINFO,MB2_tag_type(%ecx)
-        jne     1f
+        jne     2f
 
         mov     MB2_mem_lower(%ecx),%edx
-        jmp     trampoline_bios_setup
+        jmp     3f
 
-1:
+2:
         /* EFI mode is not supported via legacy BIOS path. */
         cmpl    $MULTIBOOT2_TAG_TYPE_EFI32,MB2_tag_type(%ecx)
         je      mb2_too_old
@@ -316,6 +341,7 @@ multiboot2_proto:
         cmpl    $MULTIBOOT2_TAG_TYPE_END,MB2_tag_type(%ecx)
         je      trampoline_bios_setup
 
+3:
         /* Go to next Multiboot2 information tag. */
         add     MB2_tag_size(%ecx),%ecx
         add     $(MULTIBOOT2_TAG_ALIGN-1),%ecx
diff --git a/xen/arch/x86/x86_64/asm-offsets.c 
b/xen/arch/x86/x86_64/asm-offsets.c
index b7aed49..5345a9e 100644
--- a/xen/arch/x86/x86_64/asm-offsets.c
+++ b/xen/arch/x86/x86_64/asm-offsets.c
@@ -172,6 +172,7 @@ void __dummy__(void)
     DEFINE(MB2_fixed_sizeof, sizeof(multiboot2_fixed_t));
     OFFSET(MB2_tag_type, multiboot2_tag_t, type);
     OFFSET(MB2_tag_size, multiboot2_tag_t, size);
+    OFFSET(MB2_base_addr, multiboot2_tag_base_addr_t, base_addr);
     OFFSET(MB2_mem_lower, multiboot2_tag_basic_meminfo_t, mem_lower);
     OFFSET(MB2_efi64_st, multiboot2_tag_efi64_t, pointer);
     OFFSET(MB2_efi64_ih, multiboot2_tag_efi64_ih_t, pointer);
diff --git a/xen/include/xen/multiboot2.h b/xen/include/xen/multiboot2.h
index 09ee64e..a63c4d6 100644
--- a/xen/include/xen/multiboot2.h
+++ b/xen/include/xen/multiboot2.h
@@ -59,11 +59,17 @@
 #define MULTIBOOT2_HEADER_TAG_EFI_BS                   7
 #define MULTIBOOT2_HEADER_TAG_ENTRY_ADDRESS_EFI32      8
 #define MULTIBOOT2_HEADER_TAG_ENTRY_ADDRESS_EFI64      9
+#define MULTIBOOT2_HEADER_TAG_RELOCATABLE              10
 
 /* Header tag flags. */
 #define MULTIBOOT2_HEADER_TAG_REQUIRED 0
 #define MULTIBOOT2_HEADER_TAG_OPTIONAL 1
 
+/* Where image should be loaded (suggestion not requirement). */
+#define MULTIBOOT2_LOAD_PREFERENCE_NONE        0
+#define MULTIBOOT2_LOAD_PREFERENCE_LOW 1
+#define MULTIBOOT2_LOAD_PREFERENCE_HIGH        2
+
 /* Header console tag console_flags. */
 #define MULTIBOOT2_CONSOLE_FLAGS_CONSOLE_REQUIRED      1
 #define MULTIBOOT2_CONSOLE_FLAGS_EGA_TEXT_SUPPORTED    2
@@ -90,6 +96,7 @@
 #define MULTIBOOT2_TAG_TYPE_EFI_BS             18
 #define MULTIBOOT2_TAG_TYPE_EFI32_IH           19
 #define MULTIBOOT2_TAG_TYPE_EFI64_IH           20
+#define MULTIBOOT2_TAG_TYPE_BASE_ADDR          21
 
 /* Multiboot 2 tag alignment. */
 #define MULTIBOOT2_TAG_ALIGN                   8
@@ -120,6 +127,12 @@ typedef struct {
 typedef struct {
     u32 type;
     u32 size;
+    u32 base_addr;
+} multiboot2_tag_base_addr_t;
+
+typedef struct {
+    u32 type;
+    u32 size;
     char string[0];
 } multiboot2_tag_string_t;
 
-- 
1.7.10.4


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