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Patch "x86/asm: Move 'status' from thread_struct to thread_info" has been added to the 4.9-stable tree

PATCH [email protected] 1 participant 1 message Feb 8, 2018

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This is a note to let you know that I've just added the patch titled

x86/asm: Move 'status' from thread_struct to thread_info

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-asm-move-status-from-thread_struct-to-thread_info.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From foo@baz Thu Feb 8 03:32:24 CET 2018

From: Andy Lutomirski <[email protected]>
Date: Sun, 28 Jan 2018 10:38:50 -0800
Subject: x86/asm: Move 'status' from thread_struct to thread_info

From: Andy Lutomirski <[email protected]>

(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 <[email protected]>
Signed-off-by Andy Lutomirski <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Reviewed-by Ingo Molnar <[email protected]>
Acked-by Linus Torvalds <[email protected]>
Cc Borislav Petkov <[email protected]>
Cc Kernel Hardening <[email protected]>
Link https://lkml.kernel.org/r/03148bcc1b217100e6e8ecf6a5468c45cf4304b6.1517164461.git.luto@kernel.org open here
Signed-off-by David Woodhouse <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 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(-)
arch/x86/entry/common.c +2 -2
@@ -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) {
arch/x86/include/asm/processor.h +0 -2
@@ -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;
arch/x86/include/asm/syscall.h +3 -3
@@ -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;
arch/x86/include/asm/thread_info.h +2 -1
@@ -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
 
 /*
arch/x86/kernel/process_64.c +2 -2
@@ -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);
arch/x86/kernel/ptrace.c +1 -1
@@ -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):
arch/x86/kernel/signal.c +1 -1
@@ -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

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/x86-entry-64-push-extra-regs-right-away.patch queue-4.9/kvm-vmx-allow-direct-access-to-msr_ia32_spec_ctrl.patch queue-4.9/kvm-x86-add-ibpb-support.patch queue-4.9/kvm-svm-allow-direct-access-to-msr_ia32_spec_ctrl.patch queue-4.9/x86-paravirt-remove-noreplace-paravirt-cmdline-option.patch queue-4.9/x86-asm-move-status-from-thread_struct-to-thread_info.patch queue-4.9/kvm-x86-make-indirect-calls-in-emulator-speculation-safe.patch queue-4.9/x86-entry-64-remove-the-syscall64-fast-path.patch queue-4.9/x86-asm-fix-inline-asm-call-constraints-for-gcc-4.4.patch queue-4.9/kvm-vmx-make-indirect-call-speculation-safe.patch queue-4.9/x86-spectre-fix-spelling-mistake-vunerable-vulnerable.patch queue-4.9/x86-get_user-use-pointer-masking-to-limit-speculation.patch queue-4.9/x86-syscall-sanitize-syscall-table-de-references-under-speculation.patch queue-4.9/x86-pti-make-unpoison-of-pgd-for-trusted-boot-work-for-real.patch queue-4.9/x86-pti-mark-constant-arrays-as-__initconst.patch queue-4.9/kvm-vmx-emulate-msr_ia32_arch_capabilities.patch