4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Lutomirski <l...@kernel.org>


(cherry picked from commit 37a8f7c38339b22b69876d6f5a0ab851565284e3)

The TS_COMPAT bit is very hot and is accessed from code paths that mostly
also touch thread_info::flags.  Move it into struct thread_info to improve
cache locality.

The only reason it was in thread_struct is that there was a brief period
during which arch-specific fields were not allowed in struct thread_info.

Linus suggested further changing:

  ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);

to:

  if (unlikely(ti->status & (TS_COMPAT|TS_I386_REGS_POKED)))
          ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);

on the theory that frequently dirtying the cacheline even in pure 64-bit
code that never needs to modify status hurts performance.  That could be a
reasonable followup patch, but I suspect it matters less on top of this
patch.

Suggested-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Andy Lutomirski <l...@kernel.org>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Reviewed-by: Ingo Molnar <mi...@kernel.org>
Acked-by: Linus Torvalds <torva...@linux-foundation.org>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Kernel Hardening <kernel-harden...@lists.openwall.com>
Link: 
https://lkml.kernel.org/r/03148bcc1b217100e6e8ecf6a5468c45cf4304b6.1517164461.git.l...@kernel.org
Signed-off-by: David Woodhouse <d...@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 arch/x86/entry/common.c            |    4 ++--
 arch/x86/include/asm/processor.h   |    2 --
 arch/x86/include/asm/syscall.h     |    6 +++---
 arch/x86/include/asm/thread_info.h |    3 ++-
 arch/x86/kernel/process_64.c       |    4 ++--
 arch/x86/kernel/ptrace.c           |    2 +-
 arch/x86/kernel/signal.c           |    2 +-
 7 files changed, 11 insertions(+), 12 deletions(-)

--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -201,7 +201,7 @@ __visible inline void prepare_exit_to_us
         * special case only applies after poking regs and before the
         * very next return to user mode.
         */
-       current->thread.status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
+       ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
 #endif
 
        user_enter_irqoff();
@@ -299,7 +299,7 @@ static __always_inline void do_syscall_3
        unsigned int nr = (unsigned int)regs->orig_ax;
 
 #ifdef CONFIG_IA32_EMULATION
-       current->thread.status |= TS_COMPAT;
+       ti->status |= TS_COMPAT;
 #endif
 
        if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) {
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -391,8 +391,6 @@ struct thread_struct {
        unsigned short          gsindex;
 #endif
 
-       u32                     status;         /* thread synchronous flags */
-
 #ifdef CONFIG_X86_64
        unsigned long           fsbase;
        unsigned long           gsbase;
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -60,7 +60,7 @@ static inline long syscall_get_error(str
         * TS_COMPAT is set for 32-bit syscall entries and then
         * remains set until we return to user mode.
         */
-       if (task->thread.status & (TS_COMPAT|TS_I386_REGS_POKED))
+       if (task->thread_info.status & (TS_COMPAT|TS_I386_REGS_POKED))
                /*
                 * Sign-extend the value so (int)-EFOO becomes (long)-EFOO
                 * and will match correctly in comparisons.
@@ -116,7 +116,7 @@ static inline void syscall_get_arguments
                                         unsigned long *args)
 {
 # ifdef CONFIG_IA32_EMULATION
-       if (task->thread.status & TS_COMPAT)
+       if (task->thread_info.status & TS_COMPAT)
                switch (i) {
                case 0:
                        if (!n--) break;
@@ -177,7 +177,7 @@ static inline void syscall_set_arguments
                                         const unsigned long *args)
 {
 # ifdef CONFIG_IA32_EMULATION
-       if (task->thread.status & TS_COMPAT)
+       if (task->thread_info.status & TS_COMPAT)
                switch (i) {
                case 0:
                        if (!n--) break;
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -54,6 +54,7 @@ struct task_struct;
 
 struct thread_info {
        unsigned long           flags;          /* low level flags */
+       u32                     status;         /* thread synchronous flags */
 };
 
 #define INIT_THREAD_INFO(tsk)                  \
@@ -213,7 +214,7 @@ static inline int arch_within_stack_fram
 #define in_ia32_syscall() true
 #else
 #define in_ia32_syscall() (IS_ENABLED(CONFIG_IA32_EMULATION) && \
-                          current->thread.status & TS_COMPAT)
+                          current_thread_info()->status & TS_COMPAT)
 #endif
 
 /*
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -538,7 +538,7 @@ void set_personality_ia32(bool x32)
                current->personality &= ~READ_IMPLIES_EXEC;
                /* in_compat_syscall() uses the presence of the x32
                   syscall bit flag to determine compat status */
-               current->thread.status &= ~TS_COMPAT;
+               current_thread_info()->status &= ~TS_COMPAT;
        } else {
                set_thread_flag(TIF_IA32);
                clear_thread_flag(TIF_X32);
@@ -546,7 +546,7 @@ void set_personality_ia32(bool x32)
                        current->mm->context.ia32_compat = TIF_IA32;
                current->personality |= force_personality32;
                /* Prepare the first "return" to user space */
-               current->thread.status |= TS_COMPAT;
+               current_thread_info()->status |= TS_COMPAT;
        }
 }
 EXPORT_SYMBOL_GPL(set_personality_ia32);
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -934,7 +934,7 @@ static int putreg32(struct task_struct *
                 */
                regs->orig_ax = value;
                if (syscall_get_nr(child, regs) >= 0)
-                       child->thread.status |= TS_I386_REGS_POKED;
+                       child->thread_info.status |= TS_I386_REGS_POKED;
                break;
 
        case offsetof(struct user32, regs.eflags):
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -785,7 +785,7 @@ static inline unsigned long get_nr_resta
         * than the tracee.
         */
 #ifdef CONFIG_IA32_EMULATION
-       if (current->thread.status & (TS_COMPAT|TS_I386_REGS_POKED))
+       if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
                return __NR_ia32_restart_syscall;
 #endif
 #ifdef CONFIG_X86_X32_ABI


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