This patch splits realmode and loader routines out of startup.S. The idea is that the LinuxBIOS port can be adapted to share more code with the rest of GRUB instead of duplicating it.
This is quite critical stuff, so even if the change seems trivial I'd suggest being careful, since I don't trust myself too much. Of course, I've tested that it can still boot Linux and Multiboot (on qemu only). Perhaps testing on real hardware would be appropiate (but I don't have this handy atm). -- Robert Millan <GPLv2> I know my rights; I want my phone call! <DRM> What use is a phone call, if you are unable to speak? (as seen on /.)
2007-10-16 Robert Millan <[EMAIL PROTECTED]> * kern/i386/loader.S: New file. * kern/i386/pc/startup.S (grub_linux_prot_size): Moved to ... * kern/i386/loader.S (grub_linux_prot_size): ... here. * kern/i386/pc/startup.S (grub_linux_tmp_addr): Moved to ... * kern/i386/loader.S (grub_linux_tmp_addr): ... here. * kern/i386/pc/startup.S (grub_linux_real_addr): Moved to ... * kern/i386/loader.S (grub_linux_real_addr): ... here. * kern/i386/pc/startup.S (grub_linux_boot_zimage): Moved to ... * kern/i386/loader.S (grub_linux_boot_zimage): ... here. * kern/i386/pc/startup.S (grub_linux_boot_bzimage): Moved to ... * kern/i386/loader.S (grub_linux_boot_bzimage): ... here. * kern/i386/pc/startup.S (grub_multiboot_real_boot): Moved to ... * kern/i386/loader.S (grub_multiboot_real_boot): ... here. * kern/i386/pc/startup.S (grub_multiboot2_real_boot): Moved to ... * kern/i386/loader.S (grub_multiboot2_real_boot): ... here. * kern/i386/realmode.S: New file. * kern/i386/pc/startup.S (protstack): Moved to ... * kern/i386/realmode.S (protstack): ... here. * kern/i386/pc/startup.S (gdt): Moved to ... * kern/i386/realmode.S (gdt): ... here. * kern/i386/pc/startup.S (prot_to_real): Moved to ... * kern/i386/realmode.S (prot_to_real): ... here. * kern/i386/pc/startup.S: Include `kern/i386/loader.S' and `kern/i386/realmode.S'. diff -Nurp grub2/kern/i386/loader.S grub2.split/kern/i386/loader.S --- grub2/kern/i386/loader.S 1970-01-01 01:00:00.000000000 +0100 +++ grub2.split/kern/i386/loader.S 2007-10-16 22:44:21.000000000 +0200 @@ -0,0 +1,157 @@ +/* + * GRUB -- GRand Unified Bootloader + * Copyright (C) 1999,2000,2001,2002,2003,2005,2006,2007 Free Software Foundation, Inc. + * + * GRUB 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 3 of the License, or + * (at your option) any later version. + * + * GRUB 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 GRUB. If not, see <http://www.gnu.org/licenses/>. + */ + + +/* + * Note: These functions defined in this file may be called from C. + * Be careful of that you must not modify some registers. Quote + * from gcc-2.95.2/gcc/config/i386/i386.h: + + 1 for registers not available across function calls. + These must include the FIXED_REGISTERS and also any + registers that can be used without being saved. + The latter must include the registers where values are returned + and the register where structure-value addresses are passed. + Aside from that, you can include as many other registers as you like. + + ax,dx,cx,bx,si,di,bp,sp,st,st1,st2,st3,st4,st5,st6,st7,arg +{ 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 } + */ + +/* + * Note: GRUB is compiled with the options -mrtd and -mregparm=3. + * So the first three arguments are passed in %eax, %edx, and %ecx, + * respectively, and if a function has a fixed number of arguments + * and the number if greater than three, the function must return + * with "ret $N" where N is ((the number of arguments) - 3) * 4. + */ + +/* + * This is the area for all of the special variables. + */ + + .p2align 2 /* force 4-byte alignment */ + +/* + * void grub_linux_boot_zimage (void) + */ +VARIABLE(grub_linux_prot_size) + .long 0 +VARIABLE(grub_linux_tmp_addr) + .long 0 +VARIABLE(grub_linux_real_addr) + .long 0 + +FUNCTION(grub_linux_boot_zimage) + /* copy the kernel */ + movl EXT_C(grub_linux_prot_size), %ecx + addl $3, %ecx + shrl $2, %ecx + movl $GRUB_LINUX_BZIMAGE_ADDR, %esi + movl $GRUB_LINUX_ZIMAGE_ADDR, %edi + cld + rep + movsl + +FUNCTION(grub_linux_boot_bzimage) + call EXT_C(grub_dl_unload_all) + + movl EXT_C(grub_linux_real_addr), %ebx + + /* copy the real mode code */ + movl EXT_C(grub_linux_tmp_addr), %esi + movl %ebx, %edi + movl $GRUB_LINUX_SETUP_MOVE_SIZE, %ecx + cld + rep + movsb + + /* change %ebx to the segment address */ + shrl $4, %ebx + movl %ebx, %eax + addl $0x20, %eax + movw %ax, linux_setup_seg + + /* XXX new stack pointer in safe area for calling functions */ + movl $0x4000, %esp + call EXT_C(grub_stop_floppy) + + /* final setup for linux boot */ + call prot_to_real + .code16 + + cli + movw %bx, %ss + movw $GRUB_LINUX_SETUP_STACK, %sp + + movw %bx, %ds + movw %bx, %es + movw %bx, %fs + movw %bx, %gs + + /* ljmp */ + .byte 0xea + .word 0 +linux_setup_seg: + .word 0 + .code32 + + +/* + * This starts the multiboot kernel. + */ + +FUNCTION(grub_multiboot_real_boot) + /* Push the entry address on the stack. */ + pushl %eax + /* Move the address of the multiboot information structure to ebx. */ + movl %edx,%ebx + + /* Unload all modules and stop the floppy driver. */ + call EXT_C(grub_dl_unload_all) + call EXT_C(grub_stop_floppy) + + /* Interrupts should be disabled. */ + cli + + /* Move the magic value into eax and jump to the kernel. */ + movl $MULTIBOOT_MAGIC2,%eax + popl %ecx + jmp *%ecx + +/* + * This starts the multiboot 2 kernel. + */ + +FUNCTION(grub_multiboot2_real_boot) + /* Push the entry address on the stack. */ + pushl %eax + /* Move the address of the multiboot information structure to ebx. */ + movl %edx,%ebx + + /* Unload all modules and stop the floppy driver. */ + call EXT_C(grub_dl_unload_all) + call EXT_C(grub_stop_floppy) + + /* Interrupts should be disabled. */ + cli + + /* Move the magic value into eax and jump to the kernel. */ + movl $MULTIBOOT2_BOOTLOADER_MAGIC,%eax + popl %ecx + jmp *%ecx diff -Nurp grub2/kern/i386/pc/startup.S grub2.split/kern/i386/pc/startup.S --- grub2/kern/i386/pc/startup.S 2007-07-25 21:29:24.000000000 +0200 +++ grub2.split/kern/i386/pc/startup.S 2007-10-16 22:46:25.000000000 +0200 @@ -242,6 +242,7 @@ codestart: */ call EXT_C(grub_main) +#include "kern/i386/realmode.S" /* * This is the area for all of the special variables. @@ -249,9 +250,6 @@ codestart: .p2align 2 /* force 4-byte alignment */ -protstack: - .long GRUB_MEMORY_MACHINE_PROT_STACK - VARIABLE(grub_boot_drive) .long 0 @@ -271,65 +269,7 @@ VARIABLE(grub_apm_bios_info) .word 0 /* cseg_16_len */ .word 0 /* dseg_16_len */ -/* - * This is the Global Descriptor Table - * - * An entry, a "Segment Descriptor", looks like this: - * - * 31 24 19 16 7 0 - * ------------------------------------------------------------ - * | | |B| |A| | | |1|0|E|W|A| | - * | BASE 31..24 |G|/|L|V| LIMIT |P|DPL| TYPE | BASE 23:16 | 4 - * | | |D| |L| 19..16| | |1|1|C|R|A| | - * ------------------------------------------------------------ - * | | | - * | BASE 15..0 | LIMIT 15..0 | 0 - * | | | - * ------------------------------------------------------------ - * - * Note the ordering of the data items is reversed from the above - * description. - */ - .p2align 2 /* force 4-byte alignment */ -gdt: - .word 0, 0 - .byte 0, 0, 0, 0 - - /* -- code segment -- - * base = 0x00000000, limit = 0xFFFFF (4 KiB Granularity), present - * type = 32bit code execute/read, DPL = 0 - */ - .word 0xFFFF, 0 - .byte 0, 0x9A, 0xCF, 0 - - /* -- data segment -- - * base = 0x00000000, limit 0xFFFFF (4 KiB Granularity), present - * type = 32 bit data read/write, DPL = 0 - */ - .word 0xFFFF, 0 - .byte 0, 0x92, 0xCF, 0 - - /* -- 16 bit real mode CS -- - * base = 0x00000000, limit 0x0FFFF (1 B Granularity), present - * type = 16 bit code execute/read only/conforming, DPL = 0 - */ - .word 0xFFFF, 0 - .byte 0, 0x9E, 0, 0 - - /* -- 16 bit real mode DS -- - * base = 0x00000000, limit 0x0FFFF (1 B Granularity), present - * type = 16 bit data read/write, DPL = 0 - */ - .word 0xFFFF, 0 - .byte 0, 0x92, 0, 0 - - -/* this is the GDT descriptor */ -gdtdesc: - .word 0x27 /* limit */ - .long gdt /* addr */ - /* * These next two routines, "real_to_prot" and "prot_to_real" are structured @@ -382,69 +322,6 @@ protcseg: /* return on the old (or initialized) stack! */ ret - -prot_to_real: - /* just in case, set GDT */ - lgdt gdtdesc - - /* save the protected mode stack */ - movl %esp, %eax - movl %eax, protstack - - /* get the return address */ - movl (%esp), %eax - movl %eax, GRUB_MEMORY_MACHINE_REAL_STACK - - /* set up new stack */ - movl $GRUB_MEMORY_MACHINE_REAL_STACK, %eax - movl %eax, %esp - movl %eax, %ebp - - /* set up segment limits */ - movw $GRUB_MEMORY_MACHINE_PSEUDO_REAL_DSEG, %ax - movw %ax, %ds - movw %ax, %es - movw %ax, %fs - movw %ax, %gs - movw %ax, %ss - - /* this might be an extra step */ - /* jump to a 16 bit segment */ - ljmp $GRUB_MEMORY_MACHINE_PSEUDO_REAL_CSEG, $tmpcseg - -tmpcseg: - .code16 - - /* clear the PE bit of CR0 */ - movl %cr0, %eax - andl $(~GRUB_MEMORY_MACHINE_CR0_PE_ON), %eax - movl %eax, %cr0 - - /* flush prefetch queue, reload %cs */ - DATA32 ljmp $0, $realcseg - -realcseg: - /* we are in real mode now - * set up the real mode segment registers : DS, SS, ES - */ - /* zero %eax */ - xorl %eax, %eax - - movw %ax, %ds - movw %ax, %es - movw %ax, %fs - movw %ax, %gs - movw %ax, %ss - - /* restore interrupts */ - sti - - /* return on new stack! */ - DATA32 ret - - .code32 - - /* * grub_gate_a20(int on) * @@ -730,115 +607,7 @@ FUNCTION(grub_chainloader_real_boot) ljmp $0, $GRUB_MEMORY_MACHINE_BOOT_LOADER_ADDR .code32 - -/* - * void grub_linux_boot_zimage (void) - */ -VARIABLE(grub_linux_prot_size) - .long 0 -VARIABLE(grub_linux_tmp_addr) - .long 0 -VARIABLE(grub_linux_real_addr) - .long 0 - -FUNCTION(grub_linux_boot_zimage) - /* copy the kernel */ - movl EXT_C(grub_linux_prot_size), %ecx - addl $3, %ecx - shrl $2, %ecx - movl $GRUB_LINUX_BZIMAGE_ADDR, %esi - movl $GRUB_LINUX_ZIMAGE_ADDR, %edi - cld - rep - movsl - -FUNCTION(grub_linux_boot_bzimage) - call EXT_C(grub_dl_unload_all) - - movl EXT_C(grub_linux_real_addr), %ebx - - /* copy the real mode code */ - movl EXT_C(grub_linux_tmp_addr), %esi - movl %ebx, %edi - movl $GRUB_LINUX_SETUP_MOVE_SIZE, %ecx - cld - rep - movsb - - /* change %ebx to the segment address */ - shrl $4, %ebx - movl %ebx, %eax - addl $0x20, %eax - movw %ax, linux_setup_seg - - /* XXX new stack pointer in safe area for calling functions */ - movl $0x4000, %esp - call EXT_C(grub_stop_floppy) - - /* final setup for linux boot */ - call prot_to_real - .code16 - - cli - movw %bx, %ss - movw $GRUB_LINUX_SETUP_STACK, %sp - - movw %bx, %ds - movw %bx, %es - movw %bx, %fs - movw %bx, %gs - - /* ljmp */ - .byte 0xea - .word 0 -linux_setup_seg: - .word 0 - .code32 - - -/* - * This starts the multiboot kernel. - */ - -FUNCTION(grub_multiboot_real_boot) - /* Push the entry address on the stack. */ - pushl %eax - /* Move the address of the multiboot information structure to ebx. */ - movl %edx,%ebx - - /* Unload all modules and stop the floppy driver. */ - call EXT_C(grub_dl_unload_all) - call EXT_C(grub_stop_floppy) - - /* Interrupts should be disabled. */ - cli - - /* Move the magic value into eax and jump to the kernel. */ - movl $MULTIBOOT_MAGIC2,%eax - popl %ecx - jmp *%ecx - -/* - * This starts the multiboot 2 kernel. - */ - -FUNCTION(grub_multiboot2_real_boot) - /* Push the entry address on the stack. */ - pushl %eax - /* Move the address of the multiboot information structure to ebx. */ - movl %edx,%ebx - - /* Unload all modules and stop the floppy driver. */ - call EXT_C(grub_dl_unload_all) - call EXT_C(grub_stop_floppy) - - /* Interrupts should be disabled. */ - cli - - /* Move the magic value into eax and jump to the kernel. */ - movl $MULTIBOOT2_BOOTLOADER_MAGIC,%eax - popl %ecx - jmp *%ecx +#include "kern/i386/loader.S" /* * int grub_biosdisk_rw_int13_extensions (int ah, int drive, void *dap) diff -Nurp grub2/kern/i386/realmode.S grub2.split/kern/i386/realmode.S --- grub2/kern/i386/realmode.S 1970-01-01 01:00:00.000000000 +0100 +++ grub2.split/kern/i386/realmode.S 2007-10-16 23:01:27.000000000 +0200 @@ -0,0 +1,178 @@ +/* + * GRUB -- GRand Unified Bootloader + * Copyright (C) 1999,2000,2001,2002,2003,2005,2006,2007 Free Software Foundation, Inc. + * + * GRUB 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 3 of the License, or + * (at your option) any later version. + * + * GRUB 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 GRUB. If not, see <http://www.gnu.org/licenses/>. + */ + + +/* + * Note: These functions defined in this file may be called from C. + * Be careful of that you must not modify some registers. Quote + * from gcc-2.95.2/gcc/config/i386/i386.h: + + 1 for registers not available across function calls. + These must include the FIXED_REGISTERS and also any + registers that can be used without being saved. + The latter must include the registers where values are returned + and the register where structure-value addresses are passed. + Aside from that, you can include as many other registers as you like. + + ax,dx,cx,bx,si,di,bp,sp,st,st1,st2,st3,st4,st5,st6,st7,arg +{ 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 } + */ + +/* + * Note: GRUB is compiled with the options -mrtd and -mregparm=3. + * So the first three arguments are passed in %eax, %edx, and %ecx, + * respectively, and if a function has a fixed number of arguments + * and the number if greater than three, the function must return + * with "ret $N" where N is ((the number of arguments) - 3) * 4. + */ + +/* + * This is the area for all of the special variables. + */ + + .p2align 2 /* force 4-byte alignment */ + +protstack: + .long GRUB_MEMORY_MACHINE_PROT_STACK + +/* + * This is the Global Descriptor Table + * + * An entry, a "Segment Descriptor", looks like this: + * + * 31 24 19 16 7 0 + * ------------------------------------------------------------ + * | | |B| |A| | | |1|0|E|W|A| | + * | BASE 31..24 |G|/|L|V| LIMIT |P|DPL| TYPE | BASE 23:16 | 4 + * | | |D| |L| 19..16| | |1|1|C|R|A| | + * ------------------------------------------------------------ + * | | | + * | BASE 15..0 | LIMIT 15..0 | 0 + * | | | + * ------------------------------------------------------------ + * + * Note the ordering of the data items is reversed from the above + * description. + */ + + .p2align 2 /* force 4-byte alignment */ +gdt: + .word 0, 0 + .byte 0, 0, 0, 0 + + /* -- code segment -- + * base = 0x00000000, limit = 0xFFFFF (4 KiB Granularity), present + * type = 32bit code execute/read, DPL = 0 + */ + .word 0xFFFF, 0 + .byte 0, 0x9A, 0xCF, 0 + + /* -- data segment -- + * base = 0x00000000, limit 0xFFFFF (4 KiB Granularity), present + * type = 32 bit data read/write, DPL = 0 + */ + .word 0xFFFF, 0 + .byte 0, 0x92, 0xCF, 0 + + /* -- 16 bit real mode CS -- + * base = 0x00000000, limit 0x0FFFF (1 B Granularity), present + * type = 16 bit code execute/read only/conforming, DPL = 0 + */ + .word 0xFFFF, 0 + .byte 0, 0x9E, 0, 0 + + /* -- 16 bit real mode DS -- + * base = 0x00000000, limit 0x0FFFF (1 B Granularity), present + * type = 16 bit data read/write, DPL = 0 + */ + .word 0xFFFF, 0 + .byte 0, 0x92, 0, 0 + + +/* this is the GDT descriptor */ +gdtdesc: + .word 0x27 /* limit */ + .long gdt /* addr */ + +/* + * These next routine, "prot_to_real" is structured in a very + * specific way. Be very careful when changing it. + * + * NOTE: Use of it messes up %eax and %ebp. + */ + +prot_to_real: + /* just in case, set GDT */ + lgdt gdtdesc + + /* save the protected mode stack */ + movl %esp, %eax + movl %eax, protstack + + /* get the return address */ + movl (%esp), %eax + movl %eax, GRUB_MEMORY_MACHINE_REAL_STACK + + /* set up new stack */ + movl $GRUB_MEMORY_MACHINE_REAL_STACK, %eax + movl %eax, %esp + movl %eax, %ebp + + /* set up segment limits */ + movw $GRUB_MEMORY_MACHINE_PSEUDO_REAL_DSEG, %ax + movw %ax, %ds + movw %ax, %es + movw %ax, %fs + movw %ax, %gs + movw %ax, %ss + + /* this might be an extra step */ + /* jump to a 16 bit segment */ + ljmp $GRUB_MEMORY_MACHINE_PSEUDO_REAL_CSEG, $tmpcseg + +tmpcseg: + .code16 + + /* clear the PE bit of CR0 */ + movl %cr0, %eax + andl $(~GRUB_MEMORY_MACHINE_CR0_PE_ON), %eax + movl %eax, %cr0 + + /* flush prefetch queue, reload %cs */ + DATA32 ljmp $0, $realcseg + +realcseg: + /* we are in real mode now + * set up the real mode segment registers : DS, SS, ES + */ + /* zero %eax */ + xorl %eax, %eax + + movw %ax, %ds + movw %ax, %es + movw %ax, %fs + movw %ax, %gs + movw %ax, %ss + + /* restore interrupts */ + sti + + /* return on new stack! */ + DATA32 ret + + .code32
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