Commit 7b99819d authored by Joerg Roedel's avatar Joerg Roedel Committed by Borislav Petkov
Browse files

x86/head/64: Load segment registers earlier 



Make sure segments are properly set up before setting up an IDT and
doing anything that might cause a #VC exception. This is later needed
for early exception handling.

Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20200907131613.12703-32-joro@8bytes.org
parent e04b8833

arch/x86/kernel/head_64.S

+26 −26
Original line number Diff line number Diff line
@@ -166,6 +166,32 @@ SYM_CODE_START(secondary_startup_64) 
	 */

	lgdt	early_gdt_descr(%rip)



	/* set up data segments */

	xorl %eax,%eax

	movl %eax,%ds

	movl %eax,%ss

	movl %eax,%es



	/*

	 * We don't really need to load %fs or %gs, but load them anyway

	 * to kill any stale realmode selectors.  This allows execution

	 * under VT hardware.

	 */

	movl %eax,%fs

	movl %eax,%gs



	/* Set up %gs.

	 *

	 * The base of %gs always points to fixed_percpu_data. If the

	 * stack protector canary is enabled, it is located at %gs:40.

	 * Note that, on SMP, the boot cpu uses init data section until

	 * the per cpu areas are set up.

	 */

	movl	$MSR_GS_BASE,%ecx

	movl	initial_gs(%rip),%eax

	movl	initial_gs+4(%rip),%edx

	wrmsr



	/* Check if nx is implemented */

	movl	$0x80000001, %eax

	cpuid
@@ -193,32 +219,6 @@ SYM_CODE_START(secondary_startup_64) 
	pushq $0

	popfq



	/* set up data segments */

	xorl %eax,%eax

	movl %eax,%ds

	movl %eax,%ss

	movl %eax,%es



	/*

	 * We don't really need to load %fs or %gs, but load them anyway

	 * to kill any stale realmode selectors.  This allows execution

	 * under VT hardware.

	 */

	movl %eax,%fs

	movl %eax,%gs



	/* Set up %gs.

	 *

	 * The base of %gs always points to fixed_percpu_data. If the

	 * stack protector canary is enabled, it is located at %gs:40.

	 * Note that, on SMP, the boot cpu uses init data section until

	 * the per cpu areas are set up.

	 */

	movl	$MSR_GS_BASE,%ecx

	movl	initial_gs(%rip),%eax

	movl	initial_gs+4(%rip),%edx

	wrmsr



	/* rsi is pointer to real mode structure with interesting info.

	   pass it to C */

	movq	%rsi, %rdi

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