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Re: [PATCH] memdisk plus lnxboot extension


From: Bean
Subject: Re: [PATCH] memdisk plus lnxboot extension
Date: Thu, 24 Jan 2008 03:01:33 +0800

On Jan 24, 2008 12:18 AM, Bean <address@hidden> wrote:
> On Jan 23, 2008 4:54 PM, Marco Gerards <address@hidden> wrote:
> > When is this feature useful?  Can you give an example?  More features
> > can mean more bugs, more maintainance work, etc.  If the feature is
> > not worthwhile for more than one person, I am not sure if it should be
> > included.  Perhaps a better explaination of the problem to solve,
> > instead of what the patch does might help here.
>
> the most important usage of external initrd is to overcome the size
> limit of core.img.

this is the new patch, now no need to modify grub-mkimage, use cat
just as before.


        * boot/i386/pc/lnxboot.S (data_start) : Simplify code.
        (real_code_2) : Set grub_memdisk_image_addr using initrd address.

        * include/grub/i386/pc/kernel.h : New constant
        GRUB_KENRL_MACHINE_MEMDISK_IMAGE_ADDR.
        New variable grub_memdisk_image_addr.

        * kern/i386/pc/init.c (grub_arch_memdisk_addr) : Use
        grub_memdisk_image_addr if it isn't zero.

        * kern/i386/pc/startup.S : New variable grub_memdisk_image_addr.

diff --git a/boot/i386/pc/lnxboot.S b/boot/i386/pc/lnxboot.S
index f1a4ded..25554d7 100644
--- a/boot/i386/pc/lnxboot.S
+++ b/boot/i386/pc/lnxboot.S
@@ -36,22 +36,7 @@
         .globl  start, _start

 data_start:
-       pushw   %cs
-       popw    %ds
-       xorl    %eax, %eax
-       xorl    %ebx, %ebx
-       call    data_next
-
-data_next:
-       popw    %bx
-       movw    %cs, %ax
-       shll    $4, %eax
-       leal    0x200 + data_start - data_next(%ebx,%eax), %eax
-       movzbl  setup_sects - data_next(%bx), %ecx
-       shll    $9, %ecx
-       addl    %ecx, %eax
-       movl    %eax, code32_start - data_next(%bx)
-
+       xorl    %ebp, %ebp
        jmp     linux_next

        . = data_start + 0x1F1
@@ -76,7 +61,7 @@ boot_flag:
 start:
 _start:

-       jmp linux_code
+       jmp linux_init

        .ascii  "HdrS"                  // Header signature
        .word   0x0203                  // Header version number
@@ -134,9 +119,10 @@ reg_edx:
 data_leng:
        .long   0

-linux_code:
+linux_init:

        movw    %cs:(reg_edx - start), %dx
+       movl    %cs:(code32_start - start), %ebp

 linux_next:

@@ -164,9 +150,6 @@ real_code:
        movw    %si, %ss
        movw    $(CODE_ADDR), %sp

-       pushl   %esi
-       pushl   %edi
-
        // Move itself to 0:CODE_ADDR

        cld
@@ -183,34 +166,53 @@ real_code:

 real_code_2:

-       pushw   %es
-       popw    %ds
-
-       movl    (ramdisk_image - start), %esi
-       or      %esi, %esi
+       xchgl   %ebp, %esi
+       orl     %esi, %esi
        jnz     1f
-       movl    (code32_start - start), %esi
+       movw    %ds, %si
+       shll    $4, %esi
+       addl    %ebp, %esi
 1:

+       pushw   %es
+       popw    %ds
+
        movl    $0x200, %ecx
        addl    %ecx, %esi
        movl    $DATA_ADDR, %edi

        call    move_memory

-       movsbl  %dh, %eax
-       movl    %eax, %ss:(DATA_ADDR + GRUB_KERNEL_MACHINE_INSTALL_DOS_PART)
+       // Check for the multiboot signature
+       cmpl    $0x1badb002, %ss:(DATA_ADDR + 0x50)
+       jz      1f

-       movsbl  (reg_edx + 2 - start), %eax
-       movl    %eax, %ss:(DATA_ADDR + GRUB_KERNEL_MACHINE_INSTALL_BSD_PART)
+       movl    (ramdisk_image - start), %esi
+       movl    (ramdisk_size - start), %ecx
+       movl    $(DATA_ADDR - 0x200), %edi
+       jmp     2f
+
+1:
+       movl    (ramdisk_size - start), %eax
+       or      %eax, %eax
+       jz      1f
+
+       movl    %eax, %ss:(DATA_ADDR + GRUB_KERNEL_MACHINE_MEMDISK_IMAGE_SIZE)
+       movl    (ramdisk_image - start), %eax
+       movl    %eax, %ss:(DATA_ADDR + GRUB_KERNEL_MACHINE_MEMDISK_IMAGE_ADDR)
+1:

        movl    %ss:(DATA_ADDR + GRUB_KERNEL_MACHINE_COMPRESSED_SIZE), %ecx
        addl    $(GRUB_KERNEL_MACHINE_RAW_SIZE - 0x200), %ecx

+2:
        call    move_memory

-       popl    %edi
-       popl    %esi
+       movsbl  %dh, %eax
+       movl    %eax, %ss:(DATA_ADDR + GRUB_KERNEL_MACHINE_INSTALL_DOS_PART)
+
+       movsbl  (reg_edx + 2 - start), %eax
+       movl    %eax, %ss:(DATA_ADDR + GRUB_KERNEL_MACHINE_INSTALL_BSD_PART)

        ljmp    $(DATA_ADDR >> 4), $0

@@ -261,8 +263,8 @@ move_memory:

 2:

-       leal    (%esi, %eax), %esi
-       leal    (%edi, %eax), %edi
+       addl    %eax, %esi
+       addl    %eax, %edi
        subl    %eax, %ecx
        jnz     1b

diff --git a/include/grub/i386/pc/kernel.h b/include/grub/i386/pc/kernel.h
index ca16df7..f5d8438 100644
--- a/include/grub/i386/pc/kernel.h
+++ b/include/grub/i386/pc/kernel.h
@@ -37,8 +37,11 @@
 /* The offset of GRUB_MEMDISK_IMAGE_SIZE.  */
 #define GRUB_KERNEL_MACHINE_MEMDISK_IMAGE_SIZE 0x1c

+/* The offset of GRUB_MEMDISK_IMAGE_ADDR.  */
+#define GRUB_KERNEL_MACHINE_MEMDISK_IMAGE_ADDR 0x20
+
 /* The offset of GRUB_PREFIX.  */
-#define GRUB_KERNEL_MACHINE_PREFIX             0x20
+#define GRUB_KERNEL_MACHINE_PREFIX             0x24

 /* End of the data section. */
 #define GRUB_KERNEL_MACHINE_DATA_END           0x50
@@ -66,6 +69,9 @@ extern grub_int32_t grub_install_bsd_part;
 /* The size of memory disk image, if present.  */
 extern grub_int32_t grub_memdisk_image_size;

+/* The address of memory disk image, if present.  */
+extern grub_int32_t grub_memdisk_image_addr;
+
 /* The prefix which points to the directory where GRUB modules and its
    configuration file are located.  */
 extern char grub_prefix[];
diff --git a/kern/i386/pc/init.c b/kern/i386/pc/init.c
index 0cf81d7..af6deda 100644
--- a/kern/i386/pc/init.c
+++ b/kern/i386/pc/init.c
@@ -253,9 +253,10 @@ grub_arch_modules_addr (void)
 grub_addr_t
 grub_arch_memdisk_addr (void)
 {
-  return GRUB_MEMORY_MACHINE_DECOMPRESSION_ADDR
+  return (grub_memdisk_image_addr) ? grub_memdisk_image_addr :
+    (GRUB_MEMORY_MACHINE_DECOMPRESSION_ADDR
     + (grub_kernel_image_size - GRUB_KERNEL_MACHINE_RAW_SIZE)
-    + grub_total_module_size;
+    + grub_total_module_size);
 }

 /* Return the size of the memdisk image.  */
diff --git a/kern/i386/pc/startup.S b/kern/i386/pc/startup.S
index e4101a6..5dd2e67 100644
--- a/kern/i386/pc/startup.S
+++ b/kern/i386/pc/startup.S
@@ -97,6 +97,8 @@ VARIABLE(grub_install_bsd_part)
        .long   0xFFFFFFFF
 VARIABLE(grub_memdisk_image_size)
        .long   0
+VARIABLE(grub_memdisk_image_addr)
+       .long   0
 VARIABLE(grub_prefix)
        /* to be filled by grub-mkimage */



-- 
Bean




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