Re: [PATCH 03/10] kernel: entry: Wire up syscall_work in common entry code

[Thomas Gleixner]

On Fri, Nov 13 2020 at 22:29, Gabriel Krisman Bertazi wrote:

"kernel: entry:" is not the right subsystem prefix.

git log kernel/entry/ might give you a hint.

> Prepares the common entry code to use the SYSCALL_WORK flags. They
> will

s/Prepares/Prepare/

> 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 
> ---
>  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..5a4bb72ff28e 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;
>  
> @@ -75,10 +75,11 @@ static __always_inline long
>  __syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
>  {
>   unsigned long ti_work;
> + unsigned long work = READ_ONCE(current_thread_info()->syscall_work);

Even if this is temporary this code uses reverse fir tree ordering of
variable declarations:

unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
unsigned long ti_work;

Thanks,

tglx

[PATCH 03/10] kernel: entry: Wire up syscall_work in common entry code

[Gabriel Krisman Bertazi]

Prepares 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 
---
 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..5a4bb72ff28e 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;
 
@@ -75,10 +75,11 @@ static __always_inline long
 __syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
 {
unsigned long ti_work;
+   unsigned long work = READ_ONCE(current_thread_info()->syscall_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;
 
@@ -246,6 +248,7 @@ 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)
 {
u32 cached_flags = READ_ONCE(current_thread_info()->flags);
+   unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
unsigned long nr = syscall_get_nr(current, regs);
 
CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
@@ -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