linux-kernel - [PATCH v2 03/10] entry: Wire up syscall

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Date:   Mon, 16 Nov 2020 12:41:59 -0500
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     tglx@...utronix.de
Cc:     hch@...radead.org, mingo@...hat.com, keescook@...omium.org,
        arnd@...db.de, luto@...capital.net, wad@...omium.org,
        rostedt@...dmis.org, paul@...l-moore.com, eparis@...hat.com,
        oleg@...hat.com, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel@...labora.com
Subject: [PATCH v2 03/10] entry: Wire up syscall_work in common entry code

Prepare the common entry code to use the SYSCALL_WORK flags. They will
be defined in subsequent patches for each type of syscall
work. SYSCALL_WORK_ENTRY/EXIT are defined for the transition, as they
will replace the TIF_ equivalent defines.

Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>

---
Changes since v2:
  - Fix subsystem prefix (tglx)
  - Fix verb in commit message (tglx)
  - Sort variable declaration (tglx)
---
 include/linux/entry-common.h |  3 +++
 kernel/entry/common.c        | 15 +++++++++------
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 1a128baf3628..cbc5c702ee4d 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -64,6 +64,9 @@
 	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT |			\
 	 _TIF_SYSCALL_TRACEPOINT | ARCH_SYSCALL_EXIT_WORK)
 
+#define SYSCALL_WORK_ENTER	(0)
+#define SYSCALL_WORK_EXIT	(0)
+
 /*
  * TIF flags handled in exit_to_user_mode_loop()
  */
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index bc75c114c1b3..51c25f774791 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -42,7 +42,7 @@ static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
 }
 
 static long syscall_trace_enter(struct pt_regs *regs, long syscall,
-				unsigned long ti_work)
+				unsigned long ti_work, unsigned long work)
 {
 	long ret = 0;
 
@@ -74,11 +74,12 @@ static long syscall_trace_enter(struct pt_regs *regs, long syscall,
 static __always_inline long
 __syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
 {
+	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
 	unsigned long ti_work;
 
 	ti_work = READ_ONCE(current_thread_info()->flags);
-	if (ti_work & SYSCALL_ENTER_WORK)
-		syscall = syscall_trace_enter(regs, syscall, ti_work);
+	if (work & SYSCALL_WORK_ENTER || ti_work & SYSCALL_ENTER_WORK)
+		syscall = syscall_trace_enter(regs, syscall, ti_work, work);
 
 	return syscall;
 }
@@ -225,7 +226,8 @@ static inline bool report_single_step(unsigned long ti_work)
 }
 #endif
 
-static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work)
+static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work,
+			      unsigned long work)
 {
 	bool step;
 
@@ -245,6 +247,7 @@ static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work)
  */
 static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
 {
+	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
 	u32 cached_flags = READ_ONCE(current_thread_info()->flags);
 	unsigned long nr = syscall_get_nr(current, regs);
 
@@ -262,8 +265,8 @@ static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
 	 * enabled, we want to run them exactly once per syscall exit with
 	 * interrupts enabled.
 	 */
-	if (unlikely(cached_flags & SYSCALL_EXIT_WORK))
-		syscall_exit_work(regs, cached_flags);
+	if (unlikely(work & SYSCALL_WORK_EXIT || cached_flags & SYSCALL_EXIT_WORK))
+		syscall_exit_work(regs, cached_flags, work);
 }
 
 __visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
-- 
2.29.2