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[PATCHv5 12/21] arm64: don't reload GPRs after apply_ssbd

Now that all of the syscall logic works on the saved pt_regs, apply_ssbd
can safely corrupt x0-x3 in the entry paths, and we no longer need to
restore them. So let's remove the logic doing so.

With that logic gone, we can fold the branch target into the macro, so
that callers need not deal with this. GAS provides \@, which provides a
unique value per macro invocation, which we can use to create a unique

Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
 arch/arm64/kernel/entry.S | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index c41b84d06644..22b240da949b 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -130,20 +130,21 @@ alternative_else_nop_endif
 	// This macro corrupts x0-x3. It is the caller's duty
 	// to save/restore them if required.
-	.macro	apply_ssbd, state, targ, tmp1, tmp2
+	.macro	apply_ssbd, state, tmp1, tmp2
 alternative_cb	arm64_enable_wa2_handling
-	b	\targ
+	b	.L__asm_ssbd_skip\@
 	ldr_this_cpu	\tmp2, arm64_ssbd_callback_required, \tmp1
-	cbz	\tmp2, \targ
+	cbz	\tmp2,	.L__asm_ssbd_skip\@
 	ldr	\tmp2, [tsk, #TSK_TI_FLAGS]
-	tbnz	\tmp2, #TIF_SSBD, \targ
+	tbnz	\tmp2, #TIF_SSBD, .L__asm_ssbd_skip\@
 	mov	w1, #\state
 alternative_cb	arm64_update_smccc_conduit
 	nop					// Patched to SMC/HVC #0
@@ -173,13 +174,7 @@ alternative_cb_end
 	ldr	x19, [tsk, #TSK_TI_FLAGS]	// since we can unmask debug
 	disable_step_tsk x19, x20		// exceptions when scheduling.
-	apply_ssbd 1, 1f, x22, x23
-	ldp	x0, x1, [sp, #16 * 0]
-	ldp	x2, x3, [sp, #16 * 1]
+	apply_ssbd 1, x22, x23
 	mov	x29, xzr			// fp pointed to user-space
@@ -321,8 +316,7 @@ alternative_if ARM64_WORKAROUND_845719
-	apply_ssbd 0, 5f, x0, x1
+	apply_ssbd 0, x0, x1
 	msr	elr_el1, x21			// set up the return data