Re: Compiling grub2 on *BSD?

[Bean]

On Jan 27, 2008 1:21 AM, Robert Millan <address@hidden> wrote:
> > FreeBSD:
> >
> > lnxboot.S: Assembler messages:
> > lnxboot.S:49: Error: `0x200+data_start - data_next(%ebx,%eax)' is not a
> > valid 16 bit base/index expression
> > lnxboot.S:264: Error: `(%esi,%eax)' is not a valid 16 bit base/index
> > expression
> > lnxboot.S:265: Error: `(%edi,%eax)' is not a valid 16 bit base/index
> > expression
>
> I recall having seen this before.  Please, can you check the list archives?
> I think we solved it for other files, but it might have been respawned in
> lnxboot.S.

yes, this is caused by a trick to use 32-bit address mode for fast
arithmetic. here is the patch, along with some code cleanup for
lnxboot.S.

diff --git a/boot/i386/pc/lnxboot.S b/boot/i386/pc/lnxboot.S
index f1a4ded..81d8e40 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 +166,45 @@ 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    %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 +255,8 @@ move_memory:

 2:

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




-- 
Bean