x86/boot: Remove KEEP_SEGMENTS support

Commit a24e785111a3 ("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 ecda85e70277 ("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: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200202171353.3736319-2-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

diff --git a/Documentation/x86/boot.rst b/Documentation/x86/boot.rst
index c9c2015..fa7ddc0 100644 (file)
--- a/Documentation/x86/boot.rst
+++ b/Documentation/x86/boot.rst
@@ -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+        - This flag is obsolete.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
 

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 73f17d0..cb2cb91 100644 (file)
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -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

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 1f1f6c8..bd44d89 100644 (file)
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -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

diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 3923ab4..f66a6b9 100644 (file)
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -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
 
 /*