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Subject[PATCH 4.9 55/92] x86/asm: Move status from thread_struct to thread_info
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Andy Lutomirski <luto@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 <torvalds@linux-foundation.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Kernel Hardening <kernel-hardening@lists.openwall.com>
Link: https://lkml.kernel.org/r/03148bcc1b217100e6e8ecf6a5468c45cf4304b6.1517164461.git.luto@kernel.org
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@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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