4 files changed, 63 insertions, 6 deletions

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index f35ea2237522..a0ae2e7f6cec 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -27,13 +27,22 @@
 #include <asm/segment.h>
 #include <asm/page.h>
 #include <asm/boot.h>
+#include <asm/asm-offsets.h>
 
 .section ".text.head","ax",@progbits
         .globl startup_32
 
 startup_32:
-        cld
-        cli
+        /* check to see if KEEP_SEGMENTS flag is meaningful */
+        cmpw $0x207, BP_version(%esi)
+        jb 1f
+
+        /* test KEEP_SEGMENTS flag to see if the bootloader is asking
+         * us to not reload segments */
+        testb $(1<<6), BP_loadflags(%esi)
+        jnz 2f
+
+1:      cli
         movl $(__BOOT_DS),%eax
         movl %eax,%ds
         movl %eax,%es
@@ -41,6 +50,8 @@ startup_32:
         movl %eax,%gs
         movl %eax,%ss
 
+2:      cld
+
 /* Calculate the delta between where we were compiled to run
  * at and where we were actually loaded at.  This can only be done
  * with a short local call on x86.  Nothing  else will tell us what
diff --git a/arch/x86/boot/compressed/misc_32.c b/arch/x86/boot/compressed/misc_32.c
index 1dc1e19c0a9f..b74d60d1b2fa 100644
--- a/arch/x86/boot/compressed/misc_32.c
+++ b/arch/x86/boot/compressed/misc_32.c
@@ -247,6 +247,9 @@ static void putstr(const char *s)
         int x,y,pos;
         char c;
 
+        if (RM_SCREEN_INFO.orig_video_mode == 0 && lines == 0 && cols == 0)
+                return;
+
         x = RM_SCREEN_INFO.orig_x;
         y = RM_SCREEN_INFO.orig_y;
 
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index f3140e596d40..8353c81c41c0 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -119,7 +119,7 @@ _start:
         # Part 2 of the header, from the old setup.S
 
                 .ascii  "HdrS"          # header signature
-                .word   0x0206          # header version number (>= 0x0105)
+                .word   0x0207          # header version number (>= 0x0105)
                                         # or else old loadlin-1.5 will fail)
                 .globl realmode_swtch
 realmode_swtch: .word   0, 0            # default_switch, SETUPSEG
@@ -214,6 +214,11 @@ cmdline_size:   .long   COMMAND_LINE_SIZE-1     #length of the command line,
                                                 #added with boot protocol
                                                 #version 2.06
 
+hardware_subarch:       .long 0                 # subarchitecture, added with 2.07
+                                                # default to 0 for normal x86 PC
+
+hardware_subarch_data:  .quad 0
+
 # End of setup header #####################################################
 
         .section ".inittext", "ax"
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 39677965e161..00b1c2c56454 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -79,22 +79,30 @@ INIT_MAP_BEYOND_END = BOOTBITMAP_SIZE + (PAGE_TABLE_SIZE + ALLOCATOR_SLOP)*PAGE_
  */
 .section .text.head,"ax",@progbits
 ENTRY(startup_32)
+        /* check to see if KEEP_SEGMENTS flag is meaningful */
+        cmpw $0x207, BP_version(%esi)
+        jb 1f
+
+        /* test KEEP_SEGMENTS flag to see if the bootloader is asking
+                us to not reload segments */
+        testb $(1<<6), BP_loadflags(%esi)
+        jnz 2f
 
 /*
  * Set segments to known values.
  */
-        cld
-        lgdt boot_gdt_descr - __PAGE_OFFSET
+1:      lgdt boot_gdt_descr - __PAGE_OFFSET
         movl $(__BOOT_DS),%eax
         movl %eax,%ds
         movl %eax,%es
         movl %eax,%fs
         movl %eax,%gs
+2:
 
 /*
  * Clear BSS first so that there are no surprises...
- * No need to cld as DF is already clear from cld above...
  */
+        cld
         xorl %eax,%eax
         movl $__bss_start - __PAGE_OFFSET,%edi
         movl $__bss_stop - __PAGE_OFFSET,%ecx
@@ -128,6 +136,35 @@ ENTRY(startup_32)
         movsl
 1:
 
+#ifdef CONFIG_PARAVIRT
+        cmpw $0x207, (boot_params + BP_version - __PAGE_OFFSET)
+        jb default_entry
+
+        /* Paravirt-compatible boot parameters.  Look to see what architecture
+                we're booting under. */
+        movl (boot_params + BP_hardware_subarch - __PAGE_OFFSET), %eax
+        cmpl $num_subarch_entries, %eax
+        jae bad_subarch
+
+        movl subarch_entries - __PAGE_OFFSET(,%eax,4), %eax
+        subl $__PAGE_OFFSET, %eax
+        jmp *%eax
+
+bad_subarch:
+WEAK(lguest_entry)
+WEAK(xen_entry)
+        /* Unknown implementation; there's really
+           nothing we can do at this point. */
+        ud2a
+.data
+subarch_entries:
+        .long default_entry             /* normal x86/PC */
+        .long lguest_entry              /* lguest hypervisor */
+        .long xen_entry                 /* Xen hypervisor */
+num_subarch_entries = (. - subarch_entries) / 4
+.previous
+#endif /* CONFIG_PARAVIRT */
+
 /*
  * Initialize page tables.  This creates a PDE and a set of page
  * tables, which are located immediately beyond _end.  The variable
@@ -140,6 +177,7 @@ ENTRY(startup_32)
  */
 page_pde_offset = (__PAGE_OFFSET >> 20);
 
+default_entry:
         movl $(pg0 - __PAGE_OFFSET), %edi
         movl $(swapper_pg_dir - __PAGE_OFFSET), %edx
         movl $0x007, %eax                       /* 0x007 = PRESENT+RW+USER */