diff options
| -rw-r--r-- | arch/x86/boot/pmjump.S | 44 |
1 files changed, 32 insertions, 12 deletions
diff --git a/arch/x86/boot/pmjump.S b/arch/x86/boot/pmjump.S index fa6bed1fac1..ef0da1f2c7f 100644 --- a/arch/x86/boot/pmjump.S +++ b/arch/x86/boot/pmjump.S @@ -29,12 +29,13 @@ */ protected_mode_jump: movl %edx, %esi # Pointer to boot_params table - movl %eax, 2f # Patch ljmpl instruction + + xorl %ebx, %ebx + movw %cs, %bx + shll $4, %ebx + addl %ebx, 2f movw $__BOOT_DS, %cx - xorl %ebx, %ebx # Per the 32-bit boot protocol - xorl %ebp, %ebp # Per the 32-bit boot protocol - xorl %edi, %edi # Per the 32-bit boot protocol movl %cr0, %edx orb $1, %dl # Protected mode (PE) bit @@ -42,15 +43,34 @@ protected_mode_jump: jmp 1f # Short jump to serialize on 386/486 1: - movw %cx, %ds - movw %cx, %es - movw %cx, %fs - movw %cx, %gs - movw %cx, %ss - - # Jump to the 32-bit entrypoint + # Transition to 32-bit mode .byte 0x66, 0xea # ljmpl opcode -2: .long 0 # offset +2: .long in_pm32 # offset .word __BOOT_CS # segment .size protected_mode_jump, .-protected_mode_jump + + .code32 + .type in_pm32, @function +in_pm32: + # Set up data segments for flat 32-bit mode + movl %ecx, %ds + movl %ecx, %es + movl %ecx, %fs + movl %ecx, %gs + movl %ecx, %ss + # The 32-bit code sets up its own stack, but this way we do have + # a valid stack if some debugging hack wants to use it. + addl %ebx, %esp + + # Clear registers to allow for future extensions to the + # 32-bit boot protocol + xorl %ecx, %ecx + xorl %edx, %edx + xorl %ebx, %ebx + xorl %ebp, %ebp + xorl %edi, %edi + + jmpl *%eax # Jump to the 32-bit entrypoint + + .size in_pm32, .-in_pm32 |