Remove the redundant nested conditional check within the system call
exit path of el0_svc_common() to streamline the exit sequence.
The fast-path block is guarded by `!IS_ENABLED(CONFIG_DEBUG_RSEQ)`,
so CONFIG_DEBUG_RSEQ is guaranteed to be disabled and the call of
rseq_syscall() is a no-op. Under this constraint, the code logic
inside the block becomes completely identical to what
the arm64_syscall_exit_to_user_mode_work() helper already does.
Replace that nested logic with a direct invocation of the helper,
eliminating redundant code.
Before:
| if (... && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
| flags = read_thread_flags();
| if (unlikely(flags & _TIF_SYSCALL_EXIT_WORK) || flags & _TIF_SINGLESTEP)
| arm64_syscall_exit_to_user_mode_work(regs);
| return;
| }
| trace_exit:
| arm64_syscall_exit_to_user_mode_work(regs);
After simplify:
| if (... && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
| arm64_syscall_exit_to_user_mode_work(regs);
| return;
| }
| trace_exit:
| arm64_syscall_exit_to_user_mode_work(regs);
Furthermore, Since both the conditional fast-path and the fallback
slow-path now uniformly invoke arm64_syscall_exit_to_user_mode_work(),
this explicit conditional branch is entirely redundant regardless of
whether the evaluation is true or false. Removing it collapses
the duplicated logic into a single, unconditional path.
Also remove has_syscall_work(). No functional changes indeed.
Cc: Mark Rutland <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Ada Couprie Diaz <[email protected]>
Reviewed-by: Linus Walleij <[email protected]>
Signed-off-by: Jinjie Ruan <[email protected]>
---
arch/arm64/kernel/syscall.c | 20 +-------------------
1 file changed, 1 insertion(+), 19 deletions(-)
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index f1f0b6f3e32b..3488afd45d20 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -54,11 +54,6 @@ static void invoke_syscall(struct pt_regs *regs, unsigned
int scno,
syscall_set_return_value(current, regs, 0, ret);
}
-static inline bool has_syscall_work(unsigned long flags)
-{
- return unlikely(flags & _TIF_SYSCALL_WORK);
-}
-
static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
const syscall_fn_t syscall_table[])
{
@@ -95,7 +90,7 @@ static void el0_svc_common(struct pt_regs *regs, int scno,
int sc_nr,
return;
}
- if (has_syscall_work(flags)) {
+ if (unlikely(flags & _TIF_SYSCALL_WORK)) {
/*
* The de-facto standard way to skip a system call using ptrace
* is to set the system call to -1 (NO_SYSCALL) and set x0 to a
@@ -119,19 +114,6 @@ static void el0_svc_common(struct pt_regs *regs, int scno,
int sc_nr,
}
invoke_syscall(regs, scno, sc_nr, syscall_table);
-
- /*
- * The tracing status may have changed under our feet, so we have to
- * check again. However, if we were tracing entry, then we always trace
- * exit regardless, as the old entry assembly did.
- */
- if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
- flags = read_thread_flags();
- if (unlikely(flags & _TIF_SYSCALL_EXIT_WORK) || flags &
_TIF_SINGLESTEP)
- arm64_syscall_exit_to_user_mode_work(regs);
- return;
- }
-
trace_exit:
arm64_syscall_exit_to_user_mode_work(regs);
}
--
2.34.1
