linux-kernel - [PATCH] MIPS: Sanitise Cavium switch cases in TLB handler synthesizers

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Message-ID: <alpine.DEB.2.21.2203042044580.47558@angie.orcam.me.uk>
Date:   Fri, 4 Mar 2022 21:13:11 +0000 (GMT)
From:   "Maciej W. Rozycki" <macro@...am.me.uk>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] MIPS: Sanitise Cavium switch cases in TLB handler
 synthesizers

It makes no sense to fall through to `break'.  Therefore reorder the 
switch statements so as to have the Cavium cases first, followed by the 
default case, which improves readability and pacifies code analysis 
tools.  No change in semantics, assembly produced is exactly the same.

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Maciej W. Rozycki <macro@...am.me.uk>
Fixes: bc431d2153cc ("MIPS: Fix fall-through warnings for Clang")
---
 arch/mips/mm/tlbex.c |   23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

linux-mips-tlbex-cavium-odd-switch.diff
Index: linux-macro/arch/mips/mm/tlbex.c
===================================================================
--- linux-macro.orig/arch/mips/mm/tlbex.c
+++ linux-macro/arch/mips/mm/tlbex.c
@@ -2160,16 +2160,14 @@ static void build_r4000_tlb_load_handler
 		uasm_i_tlbr(&p);

 		switch (current_cpu_type()) {
-		default:
-			if (cpu_has_mips_r2_exec_hazard) {
-				uasm_i_ehb(&p);
-			fallthrough;
-
 		case CPU_CAVIUM_OCTEON:
 		case CPU_CAVIUM_OCTEON_PLUS:
 		case CPU_CAVIUM_OCTEON2:
-				break;
-			}
+			break;
+		default:
+			if (cpu_has_mips_r2_exec_hazard)
+				uasm_i_ehb(&p);
+			break;
 		}

 		/* Examine  entrylo 0 or 1 based on ptr. */
@@ -2236,15 +2234,14 @@ static void build_r4000_tlb_load_handler
 		uasm_i_tlbr(&p);

 		switch (current_cpu_type()) {
-		default:
-			if (cpu_has_mips_r2_exec_hazard) {
-				uasm_i_ehb(&p);
-
 		case CPU_CAVIUM_OCTEON:
 		case CPU_CAVIUM_OCTEON_PLUS:
 		case CPU_CAVIUM_OCTEON2:
-				break;
-			}
+			break;
+		default:
+			if (cpu_has_mips_r2_exec_hazard)
+				uasm_i_ehb(&p);
+			break;
 		}

 		/* Examine  entrylo 0 or 1 based on ptr. */