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Commit 9f259cc5 authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

x86 setup: set %ebx == %ebp == %edi == 0 on protected mode entry 



In accordance with the newly formalized 32-bit boot protocol, set
%ebx == %ebp == %edi == 0 in order to support future extensions to the
protocol.

Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent 7ed19290

arch/x86/boot/pmjump.S

+3 −1
Original line number Original line Diff line number Diff line
@@ -28,11 +28,13 @@ 
 * void protected_mode_jump(u32 entrypoint, u32 bootparams);

 * void protected_mode_jump(u32 entrypoint, u32 bootparams);

 */

 */

protected_mode_jump:

protected_mode_jump:

	xorl	%ebx, %ebx		# Flag to indicate this is a boot

	movl	%edx, %esi		# Pointer to boot_params table

	movl	%edx, %esi		# Pointer to boot_params table

	movl	%eax, 2f		# Patch ljmpl instruction

	movl	%eax, 2f		# Patch ljmpl instruction





	movw	$__BOOT_DS, %cx

	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

	movl	%cr0, %edx

	orb	$1, %dl			# Protected mode (PE) bit

	orb	$1, %dl			# Protected mode (PE) bit