[RFC 4/7] x86/asm: Fix assumptions that the HW TSS is at the beginning of cpu_tss

[Andy Lutomirski <luto@kernel.org>]

I'm going to move SYSENTER_stack to the beginning of cpu_tss to help
detect overflow.  Before this can happen, I need to fix several code
paths that hardcode assumptions about the old layout.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/include/asm/desc.h      |  2 +-
 arch/x86/include/asm/processor.h |  4 ++--
 arch/x86/kernel/cpu/common.c     |  4 ++--
 arch/x86/kernel/doublefault.c    | 36 +++++++++++++++++-------------------
 arch/x86/power/cpu.c             | 13 +++++++------
 5 files changed, 29 insertions(+), 30 deletions(-)

diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index 92ad5c354d11..ad35544d9e00 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -177,7 +177,7 @@ static inline void set_tssldt_descriptor(void *d, unsigned long addr,
 #endif
 }
 
-static inline void __set_tss_desc(unsigned cpu, unsigned int entry, void *addr)
+static inline void __set_tss_desc(unsigned cpu, unsigned int entry, struct x86_hw_tss *addr)
 {
 	struct desc_struct *d = get_cpu_gdt_rw(cpu);
 	tss_desc tss;
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 0644f888b12c..301d41ca1fa1 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -161,7 +161,7 @@ enum cpuid_regs_idx {
 extern struct cpuinfo_x86	boot_cpu_data;
 extern struct cpuinfo_x86	new_cpu_data;
 
-extern struct tss_struct	doublefault_tss;
+extern struct x86_hw_tss	doublefault_tss;
 extern __u32			cpu_caps_cleared[NCAPINTS];
 extern __u32			cpu_caps_set[NCAPINTS];
 
@@ -321,7 +321,7 @@ struct x86_hw_tss {
 #define IO_BITMAP_BITS			65536
 #define IO_BITMAP_BYTES			(IO_BITMAP_BITS/8)
 #define IO_BITMAP_LONGS			(IO_BITMAP_BYTES/sizeof(long))
-#define IO_BITMAP_OFFSET		offsetof(struct tss_struct, io_bitmap)
+#define IO_BITMAP_OFFSET		(offsetof(struct tss_struct, io_bitmap) - offsetof(struct tss_struct, x86_tss))
 #define INVALID_IO_BITMAP_OFFSET	0x8000
 
 struct tss_struct {
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 2cb394dc4153..ce3b3c79fc0c 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1576,7 +1576,7 @@ void cpu_init(void)
 	 * Initialize the TSS.  Don't bother initializing sp0, as the initial
 	 * task never enters user mode.
 	 */
-	set_tss_desc(cpu, t);
+	set_tss_desc(cpu, &t->x86_tss);
 	load_TR_desc();
 
 	load_mm_ldt(&init_mm);
@@ -1634,7 +1634,7 @@ void cpu_init(void)
 	 * Initialize the TSS.  Don't bother initializing sp0, as the initial
 	 * task never enters user mode.
 	 */
-	set_tss_desc(cpu, t);
+	set_tss_desc(cpu, &t->x86_tss);
 	load_TR_desc();
 
 	load_mm_ldt(&init_mm);
diff --git a/arch/x86/kernel/doublefault.c b/arch/x86/kernel/doublefault.c
index f9c324e08d85..a9fe79d49d39 100644
--- a/arch/x86/kernel/doublefault.c
+++ b/arch/x86/kernel/doublefault.c
@@ -49,25 +49,23 @@ static void doublefault_fn(void)
 		cpu_relax();
 }
 
-struct tss_struct doublefault_tss __cacheline_aligned = {
-	.x86_tss = {
-		.sp0		= STACK_START,
-		.ss0		= __KERNEL_DS,
-		.ldt		= 0,
-		.io_bitmap_base	= INVALID_IO_BITMAP_OFFSET,
-
-		.ip		= (unsigned long) doublefault_fn,
-		/* 0x2 bit is always set */
-		.flags		= X86_EFLAGS_SF | 0x2,
-		.sp		= STACK_START,
-		.es		= __USER_DS,
-		.cs		= __KERNEL_CS,
-		.ss		= __KERNEL_DS,
-		.ds		= __USER_DS,
-		.fs		= __KERNEL_PERCPU,
-
-		.__cr3		= __pa_nodebug(swapper_pg_dir),
-	}
+struct x86_hw_tss doublefault_tss __cacheline_aligned = {
+	.sp0		= STACK_START,
+	.ss0		= __KERNEL_DS,
+	.ldt		= 0,
+	.io_bitmap_base	= INVALID_IO_BITMAP_OFFSET,
+
+	.ip		= (unsigned long) doublefault_fn,
+	/* 0x2 bit is always set */
+	.flags		= X86_EFLAGS_SF | 0x2,
+	.sp		= STACK_START,
+	.es		= __USER_DS,
+	.cs		= __KERNEL_CS,
+	.ss		= __KERNEL_DS,
+	.ds		= __USER_DS,
+	.fs		= __KERNEL_PERCPU,
+
+	.__cr3		= __pa_nodebug(swapper_pg_dir),
 };
 
 /* dummy for do_double_fault() call */
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index 84fcfde53f8f..50593e138281 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -165,12 +165,13 @@ static void fix_processor_context(void)
 	struct desc_struct *desc = get_cpu_gdt_rw(cpu);
 	tss_desc tss;
 #endif
-	set_tss_desc(cpu, t);	/*
-				 * This just modifies memory; should not be
-				 * necessary. But... This is necessary, because
-				 * 386 hardware has concept of busy TSS or some
-				 * similar stupidity.
-				 */
+
+	/*
+	 * This just modifies memory; should not be necessary. But... This is
+	 * necessary, because 386 hardware has concept of busy TSS or some
+	 * similar stupidity.
+	 */
+	set_tss_desc(cpu, &t->x86_tss);
 
 #ifdef CONFIG_X86_64
 	memcpy(&tss, &desc[GDT_ENTRY_TSS], sizeof(tss_desc));
-- 
2.13.6