linux-kernel - [PATCH v3 14/20] x86/bugs: Remove default case for fully switched enums

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Message-ID: <fcf6feefab991b72e411c2aed688b18e65e06aed.1693889988.git.jpoimboe@kernel.org>
Date:   Mon,  4 Sep 2023 22:04:58 -0700
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Babu Moger <babu.moger@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, David.Kaplan@....com,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Nikolay Borisov <nik.borisov@...e.com>,
        gregkh@...uxfoundation.org, Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v3 14/20] x86/bugs: Remove default case for fully switched enums

For enum switch statements which handle all possible cases, remove the
default case so a compiler warning gets printed if one of the enums gets
accidentally omitted from the switch statement.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 arch/x86/kernel/cpu/bugs.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 4f1ad2350f49..941ac94ad0d4 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1019,7 +1019,6 @@ static void __init retbleed_select_mitigation(void)
 
 do_cmd_auto:
 	case RETBLEED_CMD_AUTO:
-	default:
 		if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
 		    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
 			if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY))
@@ -1290,6 +1289,8 @@ spectre_v2_user_select_mitigation(void)
 
 		spectre_v2_user_ibpb = mode;
 		switch (cmd) {
+		case SPECTRE_V2_USER_CMD_NONE:
+			break;
 		case SPECTRE_V2_USER_CMD_FORCE:
 		case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
 		case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
@@ -1301,8 +1302,6 @@ spectre_v2_user_select_mitigation(void)
 		case SPECTRE_V2_USER_CMD_SECCOMP:
 			static_branch_enable(&switch_mm_cond_ibpb);
 			break;
-		default:
-			break;
 		}
 
 		pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
@@ -2160,6 +2159,10 @@ static int l1d_flush_prctl_get(struct task_struct *task)
 static int ssb_prctl_get(struct task_struct *task)
 {
 	switch (ssb_mode) {
+	case SPEC_STORE_BYPASS_NONE:
+		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
+			return PR_SPEC_ENABLE;
+		return PR_SPEC_NOT_AFFECTED;
 	case SPEC_STORE_BYPASS_DISABLE:
 		return PR_SPEC_DISABLE;
 	case SPEC_STORE_BYPASS_SECCOMP:
@@ -2171,11 +2174,8 @@ static int ssb_prctl_get(struct task_struct *task)
 		if (task_spec_ssb_disable(task))
 			return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
 		return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
-	default:
-		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
-			return PR_SPEC_ENABLE;
-		return PR_SPEC_NOT_AFFECTED;
 	}
+	BUG();
 }
 
 static int ib_prctl_get(struct task_struct *task)
@@ -2504,9 +2504,6 @@ static void __init srso_select_mitigation(void)
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
                 }
 		break;
-
-	default:
-		break;
 	}
 
 out:
-- 
2.41.0