[PATCH] x86: Fix boot protocol KEEP_SEGMENTS check.

[ebiederm@xmission.com (Eric W. Biederman)]

The kernel only ever supports 1 version of the boot protocol
so there is no need to check the boot protocol revision to
see if a feature is supported.

Both x86 and x86_64 support the same boot protocol so we need
to implement the KEEP_SEGMENTS on x86_64 as well.  It isn't
just paravirt bootloaders that could use this functionality.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Vivek Goyal <vgoyal@in.ibm.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/boot/compressed/head_32.S |   12 ++++--------
 arch/x86/boot/compressed/head_64.S |    7 +++++++
 arch/x86/kernel/asm-offsets_64.c   |   10 ++++++++++
 3 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index a0ae2e7..036e635 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -33,24 +33,20 @@
 	.globl startup_32
 
 startup_32:
-	/* check to see if KEEP_SEGMENTS flag is meaningful */
-	cmpw $0x207, BP_version(%esi)
-	jb 1f
-
+	cld
 	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
 	 * us to not reload segments */
 	testb $(1<<6), BP_loadflags(%esi)
-	jnz 2f
+	jnz 1f
 
-1:	cli
+	cli
 	movl $(__BOOT_DS),%eax
 	movl %eax,%ds
 	movl %eax,%es
 	movl %eax,%fs
 	movl %eax,%gs
 	movl %eax,%ss
-
-2:	cld
+1:
 
 /* Calculate the delta between where we were compiled to run
  * at and where we were actually loaded at.  This can only be done
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 4946764..1ccb38a 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -29,6 +29,7 @@
 #include <asm/pgtable.h>
 #include <asm/page.h>
 #include <asm/msr.h>
+#include <asm/asm-offsets.h>
 
 .section ".text.head"
 	.code32
@@ -36,11 +37,17 @@
 
 startup_32:
 	cld
+	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
+	 * us to not reload segments */
+	testb $(1<<6), BP_loadflags(%esi)
+	jnz 1f
+
 	cli
 	movl	$(__KERNEL_DS), %eax
 	movl	%eax, %ds
 	movl	%eax, %es
 	movl	%eax, %ss
+1:
 
 /* Calculate the delta between where we were compiled to run
  * at and where we were actually loaded at.  This can only be done
diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index 7e50bda..d1b6ed9 100644
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -15,12 +15,16 @@
 #include <asm/segment.h>
 #include <asm/thread_info.h>
 #include <asm/ia32.h>
+#include <asm/bootparam.h>
 
 #define DEFINE(sym, val) \
         asm volatile("\n->" #sym " %0 " #val : : "i" (val))
 
 #define BLANK() asm volatile("\n->" : : )
 
+#define OFFSET(sym, str, mem) \
+	DEFINE(sym, offsetof(struct str, mem))
+
 #define __NO_STUBS 1
 #undef __SYSCALL
 #undef _ASM_X86_64_UNISTD_H_
@@ -109,5 +113,11 @@ int main(void)
 	DEFINE(crypto_tfm_ctx_offset, offsetof(struct crypto_tfm, __crt_ctx));
 	BLANK();
 	DEFINE(__NR_syscall_max, sizeof(syscalls) - 1);
+
+	BLANK();
+	OFFSET(BP_scratch, boot_params, scratch);
+	OFFSET(BP_loadflags, boot_params, hdr.loadflags);
+	OFFSET(BP_hardware_subarch, boot_params, hdr.hardware_subarch);
+	OFFSET(BP_version, boot_params, hdr.version);
 	return 0;
 }
-- 
1.5.3.rc6.17.g1911