x86/entry: Stop using PER_CPU_VAR(kernel_stack)

PER_CPU_VAR(kernel_stack) is redundant:

  - On the 64-bit build, we can use PER_CPU_VAR(cpu_tss + TSS_sp0).
  - On the 32-bit build, we can use PER_CPU_VAR(cpu_current_top_of_stack).

PER_CPU_VAR(kernel_stack) will be deleted by a separate change.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1429889495-27850-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

4 files changed, 12 insertions, 5 deletions

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 2ab0f7182df3..1b1330c07971 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -346,7 +346,7 @@ ENTRY(ia32_cstar_target)
         SWAPGS_UNSAFE_STACK
         movl    %esp,%r8d
         CFI_REGISTER    rsp,r8
-        movq    PER_CPU_VAR(kernel_stack),%rsp
+        movq    PER_CPU_VAR(cpu_tss + TSS_sp0),%rsp
         ENABLE_INTERRUPTS(CLBR_NONE)
 
         /* Zero-extending 32-bit regs, do not remove */
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index b4bdec3e9523..d656a363e1eb 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -198,9 +198,15 @@ static inline unsigned long current_stack_pointer(void)
 #else /* !__ASSEMBLY__ */
 
 /* Load thread_info address into "reg" */
+#ifdef CONFIG_X86_32
 #define GET_THREAD_INFO(reg) \
-        _ASM_MOV PER_CPU_VAR(kernel_stack),reg ; \
+        _ASM_MOV PER_CPU_VAR(cpu_current_top_of_stack),reg ; \
         _ASM_SUB $(THREAD_SIZE),reg ;
+#else
+#define GET_THREAD_INFO(reg) \
+        _ASM_MOV PER_CPU_VAR(cpu_tss + TSS_sp0),reg ; \
+        _ASM_SUB $(THREAD_SIZE),reg ;
+#endif
 
 /*
  * ASM operand which evaluates to a 'thread_info' address of
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 7423e3e2f5c5..c13b86b40176 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -216,7 +216,7 @@ ENTRY(system_call)
 GLOBAL(system_call_after_swapgs)
 
         movq    %rsp,PER_CPU_VAR(rsp_scratch)
-        movq    PER_CPU_VAR(kernel_stack),%rsp
+        movq    PER_CPU_VAR(cpu_tss + TSS_sp0),%rsp
 
         /* Construct struct pt_regs on stack */
         pushq_cfi $__USER_DS                    /* pt_regs->ss */
diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S
index a2cabb8bd6bf..5aa7ec607b9e 100644
--- a/arch/x86/xen/xen-asm_64.S
+++ b/arch/x86/xen/xen-asm_64.S
@@ -15,6 +15,7 @@
 #include <asm/percpu.h>
 #include <asm/processor-flags.h>
 #include <asm/segment.h>
+#include <asm/asm-offsets.h>
 
 #include <xen/interface/xen.h>
 
@@ -53,7 +54,7 @@ ENTRY(xen_sysret64)
          * still with the kernel gs, so we can easily switch back
          */
         movq %rsp, PER_CPU_VAR(rsp_scratch)
-        movq PER_CPU_VAR(kernel_stack), %rsp
+        movq PER_CPU_VAR(cpu_tss + TSS_sp0), %rsp
 
         pushq $__USER_DS
         pushq PER_CPU_VAR(rsp_scratch)
@@ -72,7 +73,7 @@ ENTRY(xen_sysret32)
          * still with the kernel gs, so we can easily switch back
          */
         movq %rsp, PER_CPU_VAR(rsp_scratch)
-        movq PER_CPU_VAR(kernel_stack), %rsp
+        movq PER_CPU_VAR(cpu_tss + TSS_sp0), %rsp
 
         pushq $__USER32_DS
         pushq PER_CPU_VAR(rsp_scratch)