arm64: entry.S convert el0_sync

el0_sync also unmasks exceptions on a case-by-case basis, debug exceptions
are enabled, unless this was a debug exception. Irqs are unmasked for
some exception types but not for others.

el0_dbg should run with everything masked to prevent us taking a debug
exception from do_debug_exception. For the other cases we can unmask
everything. This changes the behaviour of fpsimd_{acc,exc} and el0_inv
which previously ran with irqs masked.

This patch removed the last user of enable_dbg_and_irq, remove it.
Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Julien Thierry <julien.thierry@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/assembler.h

@@ -97,15 +97,6 @@
 9990:
 	.endm
 
-/*
- * Enable both debug exceptions and interrupts. This is likely to be
- * faster than two daifclr operations, since writes to this register
- * are self-synchronising.
- */
-	.macro	enable_dbg_and_irq
-	msr	daifclr, #(8 | 2)
-	.endm
-
 /*
  * SMP data memory barrier
  */

arch/arm64/kernel/entry.S

@@ -670,8 +670,7 @@ el0_da:
 	 * Data abort handling
 	 */
 	mrs	x26, far_el1
-	// enable interrupts before calling the main handler
-	enable_dbg_and_irq
+	enable_daif
 	ct_user_exit
 	clear_address_tag x0, x26
 	mov	x1, x25
@@ -683,8 +682,7 @@ el0_ia:
 	 * Instruction abort handling
 	 */
 	mrs	x26, far_el1
-	// enable interrupts before calling the main handler
-	enable_dbg_and_irq
+	enable_daif
 	ct_user_exit
 	mov	x0, x26
 	mov	x1, x25
@@ -695,7 +693,7 @@ el0_fpsimd_acc:
 	/*
 	 * Floating Point or Advanced SIMD access
 	 */
-	enable_dbg
+	enable_daif
 	ct_user_exit
 	mov	x0, x25
 	mov	x1, sp
@@ -705,7 +703,7 @@ el0_fpsimd_exc:
 	/*
 	 * Floating Point or Advanced SIMD exception
 	 */
-	enable_dbg
+	enable_daif
 	ct_user_exit
 	mov	x0, x25
 	mov	x1, sp
@@ -716,8 +714,7 @@ el0_sp_pc:
 	 * Stack or PC alignment exception handling
 	 */
 	mrs	x26, far_el1
-	// enable interrupts before calling the main handler
-	enable_dbg_and_irq
+	enable_daif
 	ct_user_exit
 	mov	x0, x26
 	mov	x1, x25
@@ -728,8 +725,7 @@ el0_undef:
 	/*
 	 * Undefined instruction
 	 */
-	// enable interrupts before calling the main handler
-	enable_dbg_and_irq
+	enable_daif
 	ct_user_exit
 	mov	x0, sp
 	bl	do_undefinstr
@@ -738,7 +734,7 @@ el0_sys:
 	/*
 	 * System instructions, for trapped cache maintenance instructions
 	 */
-	enable_dbg_and_irq
+	enable_daif
 	ct_user_exit
 	mov	x0, x25
 	mov	x1, sp
@@ -753,11 +749,11 @@ el0_dbg:
 	mov	x1, x25
 	mov	x2, sp
 	bl	do_debug_exception
-	enable_dbg
+	enable_daif
 	ct_user_exit
 	b	ret_to_user
 el0_inv:
-	enable_dbg
+	enable_daif
 	ct_user_exit
 	mov	x0, sp
 	mov	x1, #BAD_SYNC
@@ -836,7 +832,7 @@ el0_svc:
 	mov	wsc_nr, #__NR_syscalls
 el0_svc_naked:					// compat entry point
 	stp	x0, xscno, [sp, #S_ORIG_X0]	// save the original x0 and syscall number
-	enable_dbg_and_irq
+	enable_daif
 	ct_user_exit 1
 
 	ldr	x16, [tsk, #TSK_TI_FLAGS]	// check for syscall hooks