linux-kernel - [PATCH v4 2/2] xen/PVH: Make GDT selectors PVH-specific

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Date:   Mon, 21 May 2018 23:54:45 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Cc:     jgross@...e.com, JBeulich@...e.com,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: [PATCH v4 2/2] xen/PVH: Make GDT selectors PVH-specific

We don't need to share PVH GDT layout with other GDTs, especially
since we now have a PVH-speciific entry (for stack canary segment).

Define PVH's own selectors.

(As a side effect of this change we are also fixing improper
reference to __KERNEL_CS)

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
---
 arch/x86/xen/xen-pvh.S | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/arch/x86/xen/xen-pvh.S b/arch/x86/xen/xen-pvh.S
index 0169374..e7a5bf4 100644
--- a/arch/x86/xen/xen-pvh.S
+++ b/arch/x86/xen/xen-pvh.S
@@ -54,7 +54,11 @@
  * charge of setting up it's own stack, GDT and IDT.
  */
 
-#define PVH_GDT_ENTRY_CANARY	4
+#define PVH_GDT_ENTRY_CS	1
+#define PVH_GDT_ENTRY_DS	2
+#define PVH_GDT_ENTRY_CANARY	3
+#define PVH_CS_SEL		(PVH_GDT_ENTRY_CS * 8)
+#define PVH_DS_SEL		(PVH_GDT_ENTRY_DS * 8)
 #define PVH_CANARY_SEL		(PVH_GDT_ENTRY_CANARY * 8)
 
 ENTRY(pvh_start_xen)
@@ -62,7 +66,7 @@ ENTRY(pvh_start_xen)
 
 	lgdt (_pa(gdt))
 
-	mov $(__BOOT_DS),%eax
+	mov $PVH_DS_SEL,%eax
 	mov %eax,%ds
 	mov %eax,%es
 	mov %eax,%ss
@@ -96,7 +100,7 @@ ENTRY(pvh_start_xen)
 	mov %eax, %cr0
 
 	/* Jump to 64-bit mode. */
-	ljmp $__KERNEL_CS, $_pa(1f)
+	ljmp $PVH_CS_SEL, $_pa(1f)
 
 	/* 64-bit entry point. */
 	.code64
@@ -136,13 +140,13 @@ ENTRY(pvh_start_xen)
 	or $(X86_CR0_PG | X86_CR0_PE), %eax
 	mov %eax, %cr0
 
-	ljmp $__BOOT_CS, $1f
+	ljmp $PVH_CS_SEL, $1f
 1:
 	call xen_prepare_pvh
 	mov $_pa(pvh_bootparams), %esi
 
 	/* startup_32 doesn't expect paging and PAE to be on. */
-	ljmp $__BOOT_CS, $_pa(2f)
+	ljmp $PVH_CS_SEL, $_pa(2f)
 2:
 	mov %cr0, %eax
 	and $~X86_CR0_PG, %eax
@@ -151,7 +155,7 @@ ENTRY(pvh_start_xen)
 	and $~X86_CR4_PAE, %eax
 	mov %eax, %cr4
 
-	ljmp $__BOOT_CS, $_pa(startup_32)
+	ljmp $PVH_CS_SEL, $_pa(startup_32)
 #endif
 END(pvh_start_xen)
 
@@ -163,13 +167,12 @@ gdt:
 	.word 0
 gdt_start:
 	.quad 0x0000000000000000            /* NULL descriptor */
-	.quad 0x0000000000000000            /* reserved */
 #ifdef CONFIG_X86_64
-	.quad GDT_ENTRY(0xa09a, 0, 0xfffff) /* __KERNEL_CS */
+	.quad GDT_ENTRY(0xa09a, 0, 0xfffff) /* PVH_CS_SEL */
 #else
-	.quad GDT_ENTRY(0xc09a, 0, 0xfffff) /* __KERNEL_CS */
+	.quad GDT_ENTRY(0xc09a, 0, 0xfffff) /* PVH_CS_SEL */
 #endif
-	.quad GDT_ENTRY(0xc092, 0, 0xfffff) /* __KERNEL_DS */
+	.quad GDT_ENTRY(0xc092, 0, 0xfffff) /* PVH_DS_SEL */
 	.quad GDT_ENTRY(0x4090, 0, 0x18)    /* PVH_CANARY_SEL */
 gdt_end:
 
-- 
2.9.3