Commit 67a6af7a authored by Arvind Sankar's avatar Arvind Sankar Committed by Ard Biesheuvel
Browse files

x86/boot: Remove KEEP_SEGMENTS support 

Commit a24e7851 ("i386: paravirt boot sequence") added this flag for
use by paravirtualized environments such as Xen. However, Xen never made
use of this flag [1], and it was only ever used by lguest [2].

Commit ecda85e7 ("x86/lguest: Remove lguest support") removed
lguest, so KEEP_SEGMENTS has lost its last user.

[1] https://lore.kernel.org/lkml/4D4B097C.5050405@goop.org
[2] https://www.mail-archive.com/lguest@lists.ozlabs.org/msg00469.html



Signed-off-by: default avatarArvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200202171353.3736319-2-nivedita@alum.mit.edu


Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
parent 9f922377

Documentation/x86/boot.rst

+2 −6
Original line number Diff line number Diff line
@@ -490,15 +490,11 @@ Protocol: 2.00+ 
		kernel) to not write early messages that require

		accessing the display hardware directly.



  Bit 6 (write): KEEP_SEGMENTS

  Bit 6 (obsolete): KEEP_SEGMENTS



	Protocol: 2.07+



	- If 0, reload the segment registers in the 32bit entry point.

	- If 1, do not reload the segment registers in the 32bit entry point.



		Assume that %cs %ds %ss %es are all set to flat segments with

		a base of 0 (or the equivalent for their environment).

        - This flag is obsolete.



  Bit 7 (write): CAN_USE_HEAP

arch/x86/boot/compressed/head_32.S

+0 −8
Original line number Diff line number Diff line
@@ -63,13 +63,6 @@ 
	__HEAD

SYM_FUNC_START(startup_32)

	cld

	/*

	 * Test KEEP_SEGMENTS flag to see if the bootloader is asking

	 * us to not reload segments

	 */

	testb	$KEEP_SEGMENTS, BP_loadflags(%esi)

	jnz	1f



	cli

	movl	$__BOOT_DS, %eax

	movl	%eax, %ds
@@ -77,7 +70,6 @@ SYM_FUNC_START(startup_32) 
	movl	%eax, %fs

	movl	%eax, %gs

	movl	%eax, %ss

1:



/*

 * Calculate the delta between where we were compiled to run

arch/x86/boot/compressed/head_64.S

+0 −8
Original line number Diff line number Diff line
@@ -53,19 +53,11 @@ SYM_FUNC_START(startup_32) 
	 * all need to be under the 4G limit.

	 */

	cld

	/*

	 * Test KEEP_SEGMENTS flag to see if the bootloader is asking

	 * us to not reload segments

	 */

	testb $KEEP_SEGMENTS, BP_loadflags(%esi)

	jnz 1f



	cli

	movl	$(__BOOT_DS), %eax

	movl	%eax, %ds

	movl	%eax, %es

	movl	%eax, %ss

1:



/*

 * Calculate the delta between where we were compiled to run

arch/x86/kernel/head_32.S

+0 −6
Original line number Diff line number Diff line
@@ -67,11 +67,6 @@ __HEAD 
SYM_CODE_START(startup_32)

	movl pa(initial_stack),%ecx

	

	/* test KEEP_SEGMENTS flag to see if the bootloader is asking

		us to not reload segments */

	testb $KEEP_SEGMENTS, BP_loadflags(%esi)

	jnz 2f



/*

 * Set segments to known values.

 */
@@ -82,7 +77,6 @@ SYM_CODE_START(startup_32) 
	movl %eax,%fs

	movl %eax,%gs

	movl %eax,%ss

2:

	leal -__PAGE_OFFSET(%ecx),%esp



/*

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