- Protect multiboot info from being overwritten

[reactos.git] / reactos / boot / freeldr / freeldr / arch / i386 / arch.S

diff --git a/reactos/boot/freeldr/freeldr/arch/i386/arch.S b/reactos/boot/freeldr/freeldr/arch/i386/arch.S
index ee6ee68..5780cea 100644 (file)
--- a/reactos/boot/freeldr/freeldr/arch/i386/arch.S
+++ b/reactos/boot/freeldr/freeldr/arch/i386/arch.S
@@ -275,9 +275,11 @@ EXTERN(_DisableA20)
  * other boot loaders like Grub
  */
 
+#define MB_INFO_SIZE                90
 #define MB_INFO_FLAGS_OFFSET        0
 #define MB_INFO_BOOT_DEVICE_OFFSET  12
 #define MB_INFO_COMMAND_LINE_OFFSET 16
+#define CMDLINE_SIZE                256
 
 /*
  * We want to execute at 0x8000 (to be compatible with bootsector
@@ -285,7 +287,6 @@ EXTERN(_DisableA20)
  * above 1MB. So we let Grub load us there and then relocate
  * ourself to 0x8000
  */
-#define CMDLINE_BASE 0x7000
 #define FREELDR_BASE 0x8000
 #define INITIAL_BASE 0x200000
 
@@ -328,6 +329,31 @@ mb1:
        movw    %dx,%ds
        movw    %dx,%es
 
+       /* Check for valid multiboot signature */
+       cmpl    $MULTIBOOT_BOOTLOADER_MAGIC,%eax
+       jne     mbfail
+
+       /* Store multiboot info in a safe place */
+       movl    %ebx,%esi
+       movl    $(mb_info + INITIAL_BASE - FREELDR_BASE),%edi
+       movl    $MB_INFO_SIZE,%ecx
+       rep movsb
+
+       /* Save commandline */
+       movl    MB_INFO_FLAGS_OFFSET(%ebx),%edx
+       testl   $MB_INFO_FLAG_COMMAND_LINE,MB_INFO_FLAGS_OFFSET(%ebx)
+       jz      mb3
+       movl    MB_INFO_COMMAND_LINE_OFFSET(%ebx),%esi
+       movl    $(cmdline + INITIAL_BASE - FREELDR_BASE),%edi
+       movl    $CMDLINE_SIZE,%ecx
+mb2:   lodsb
+       stosb
+       testb   %al,%al
+       jz      mb3
+       dec     %ecx
+       jnz     mb2
+mb3:
+
        /* Copy to low mem */
        movl    $INITIAL_BASE,%esi
        movl    $FREELDR_BASE,%edi
@@ -342,8 +368,8 @@ mb1:
 
        /* Clear prefetch queue & correct CS,
         * jump to low mem */
-       ljmp    $PMODE_CS, $mb2
-mb2:
+       ljmp    $PMODE_CS, $mb4
+mb4:
        /* Reload segment selectors */
        movw    $PMODE_DS,%dx
        movw    %dx,%ds
@@ -353,39 +379,28 @@ mb2:
        movw    %dx,%ss
        movl    $STACK32ADDR,%esp
 
-       /* Check for valid multiboot signature */
-       cmpl    $MULTIBOOT_BOOTLOADER_MAGIC,%eax
-       jne     mbfail
-
+       movl    $mb_info,%ebx
        /* See if the boot device was passed in */
        movl    MB_INFO_FLAGS_OFFSET(%ebx),%edx
        testl   $MB_INFO_FLAG_BOOT_DEVICE,%edx
-       jz      mb3
+       jz      mb5
        /* Retrieve boot device info */
        movl    MB_INFO_BOOT_DEVICE_OFFSET(%ebx),%eax
        shrl    $16,%eax
        incb    %al
        movb    %al,_i386BootPartition
        movb    %ah,_i386BootDrive
-       jmp     mb4
-mb3:   /* No boot device known, assume first partition of first harddisk */
+       jmp     mb6
+mb5:   /* No boot device known, assume first partition of first harddisk */
        movb    $0x80,_i386BootDrive
        movb    $1,_i386BootPartition
-mb4:
-
-       /* Check for a command line */
-       xorl    %eax,%eax
-       testl   $MB_INFO_FLAG_COMMAND_LINE,%edx
-       jz      mb6
-       /* Copy command line to low mem*/
-       movl    MB_INFO_COMMAND_LINE_OFFSET(%ebx),%esi
-       movl    $CMDLINE_BASE,%edi
-mb5:   lodsb
-       stosb
-       testb   %al,%al
-       jnz     mb5
-       movl    $CMDLINE_BASE,%eax
 mb6:
+       /* Check for command line */
+       mov     $cmdline,%eax
+       testl   $MB_INFO_FLAG_COMMAND_LINE,MB_INFO_FLAGS_OFFSET(%ebx)
+       jnz     mb7
+       xorl    %eax,%eax
+mb7:
 
        /* GO! */
        pushl   %eax    
@@ -467,3 +482,10 @@ EXTERN(_i386BootDrive)
 
 EXTERN(_i386BootPartition)
        .long   0
+
+.bss
+mb_info:
+       .fill   MB_INFO_SIZE, 1, 0
+
+cmdline:
+       .fill   CMDLINE_SIZE, 1, 0