linux-kernel - [PATCH v4 4/4] x86: introduce restart_block->arch

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Date:   Mon, 1 Feb 2021 18:47:16 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Jan Kratochvil <jan.kratochvil@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Pedro Alves <palves@...hat.com>, Peter Anvin <hpa@...or.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [PATCH v4 4/4] x86: introduce restart_block->arch_data to kill

With this patch x86 just saves current_thread_info()->status in the
new restart_block->arch_data field, TS_COMPAT_RESTART can be removed.

Rather than saving "status" we could shift the code from
get_nr_restart_syscall() to arch_set_restart_data() and save the syscall
number in ->arch_data.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 arch/x86/include/asm/thread_info.h | 12 ++----------
 arch/x86/kernel/signal.c           |  2 +-
 include/linux/restart_block.h      |  1 +
 3 files changed, 4 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 30d1d187019f..06b740bae431 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -217,18 +217,10 @@ static inline int arch_within_stack_frames(const void * const stack,
 #ifndef __ASSEMBLY__
 #ifdef CONFIG_COMPAT
 #define TS_I386_REGS_POKED	0x0004	/* regs poked by 32-bit ptracer */
-#define TS_COMPAT_RESTART	0x0008
 
-#define arch_set_restart_data	arch_set_restart_data
+#define arch_set_restart_data(restart)	\
+	do { restart->arch_data = current_thread_info()->status; } while (0)
 
-static inline void arch_set_restart_data(struct restart_block *restart)
-{
-	struct thread_info *ti = current_thread_info();
-	if (ti->status & TS_COMPAT)
-		ti->status |= TS_COMPAT_RESTART;
-	else
-		ti->status &= ~TS_COMPAT_RESTART;
-}
 #endif
 
 #ifdef CONFIG_X86_32
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 6c26d2c3a2e4..f306e85a08a6 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -767,7 +767,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
 {
 #ifdef CONFIG_IA32_EMULATION
-	if (current_thread_info()->status & TS_COMPAT_RESTART)
+	if (current->restart_block.arch_data & TS_COMPAT)
 		return __NR_ia32_restart_syscall;
 #endif
 #ifdef CONFIG_X86_X32_ABI
diff --git a/include/linux/restart_block.h b/include/linux/restart_block.h
index bba2920e9c05..980a65594412 100644
--- a/include/linux/restart_block.h
+++ b/include/linux/restart_block.h
@@ -23,6 +23,7 @@ enum timespec_type {
  * System call restart block.
  */
 struct restart_block {
+	unsigned long arch_data;
 	long (*fn)(struct restart_block *);
 	union {
 		/* For futex_wait and futex_wait_requeue_pi */
-- 
2.25.1.362.g51ebf55