[PATCH RFC 23/28] ARM: entry: Stop exiting syscalls like IRQs

[Linus Walleij]

The syscalls are issued as software interrupts, and to this point
they were sharing code with the other exception handlers, but
this does not work with generic entry.

Make syscall_exit_to_user_mode do what irqentry_exit_to_user_mode
does at it's tail, and drop the invocations of
irqentry_exit_to_user_mode from the syscall path so that these
are now exception-exclusive.

Split ret_to_user and ret_to_user_from_irq into two distinct
execution paths.

Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
---
 arch/arm/kernel/entry-common.S | 14 ++++++++++++--
 arch/arm/kernel/entry.c        |  4 ++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 5385574c4339..e2ac6d3216b6 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -42,7 +42,6 @@ ret_fast_syscall:
 	/* do_rseq_syscall needs interrupts enabled. */
 	mov	r0, sp				@ 'regs'
 	bl	syscall_exit_to_user_mode
-	asm_irqentry_exit_to_user_mode
 
 #ifdef CONFIG_GCC_PLUGIN_STACKLEAK
 	bl	stackleak_erase_on_task_stack
@@ -62,6 +61,18 @@ ENTRY(ret_to_user)
 	enable_irq_notrace			@ enable interrupts
 	mov	r0, sp				@ 'regs'
 	bl	syscall_exit_to_user_mode
+	ldr	r1, [tsk, #TI_FLAGS]
+	movs	r1, r1, lsl #16
+	beq	1f
+	mov	r0, sp				@ 'regs'
+	bl	do_work_pending
+1:
+#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
+	bl	stackleak_erase_on_task_stack
+#endif
+	restore_user_regs
+ENDPROC(ret_to_user)
+
 ENTRY(ret_to_user_from_irq)
 	ldr	r1, [tsk, #TI_FLAGS]
 	movs	r1, r1, lsl #16
@@ -76,7 +87,6 @@ no_work_pending:
 #endif
 	restore_user_regs
 ENDPROC(ret_to_user_from_irq)
-ENDPROC(ret_to_user)
 
 /*
  * This is how we return from a fork.
diff --git a/arch/arm/kernel/entry.c b/arch/arm/kernel/entry.c
index 0e3960844b94..88a7a699306a 100644
--- a/arch/arm/kernel/entry.c
+++ b/arch/arm/kernel/entry.c
@@ -30,6 +30,10 @@ void syscall_exit_to_user_mode(struct pt_regs *regs)
 	local_irq_disable();
 	if (has_syscall_work(flags))
 		do_work_pending(regs, flags);
+
+	trace_hardirqs_on();
+	/* This context tracking call has inverse naming */
+	user_enter_callable();
 }
 
 noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)

-- 
2.46.2