x86/spectre: Simplify spectre_v2 command line parsing

commit 9005c6834c0ffdfe46afa76656bd9276cca864f6 upstream.

[dwmw2: Use ARRAY_SIZE]

Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Cc: bp@alien8.de
Link: https://lkml.kernel.org/r/1517484441-1420-3-git-send-email-dwmw@amazon.co.uk
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 7757fa5..991e053 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -261,13 +261,13 @@ static inline const char *spectre_v2_module_string(void) { return ""; }
 static void __init spec2_print_if_insecure(const char *reason)
 {
        if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
-               pr_info("%s\n", reason);
+               pr_info("%s selected on command line.\n", reason);
 }
 
 static void __init spec2_print_if_secure(const char *reason)
 {
        if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
-               pr_info("%s\n", reason);
+               pr_info("%s selected on command line.\n", reason);
 }
 
 static inline bool retp_compiler(void)
@@ -282,42 +282,68 @@ static inline bool match_option(const char *arg, int arglen, const char *opt)
        return len == arglen && !strncmp(arg, opt, len);
 }
 
+static const struct {
+       const char *option;
+       enum spectre_v2_mitigation_cmd cmd;
+       bool secure;
+} mitigation_options[] = {
+       { "off",               SPECTRE_V2_CMD_NONE,              false },
+       { "on",                SPECTRE_V2_CMD_FORCE,             true },
+       { "retpoline",         SPECTRE_V2_CMD_RETPOLINE,         false },
+       { "retpoline,amd",     SPECTRE_V2_CMD_RETPOLINE_AMD,     false },
+       { "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
+       { "auto",              SPECTRE_V2_CMD_AUTO,              false },
+};
+
 static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 {
        char arg[20];
-       int ret;
-
-       ret = cmdline_find_option(boot_command_line, "spectre_v2", arg,
-                                 sizeof(arg));
-       if (ret > 0)  {
-               if (match_option(arg, ret, "off")) {
-                       goto disable;
-               } else if (match_option(arg, ret, "on")) {
-                       spec2_print_if_secure("force enabled on command line.");
-                       return SPECTRE_V2_CMD_FORCE;
-               } else if (match_option(arg, ret, "retpoline")) {
-                       spec2_print_if_insecure("retpoline selected on command line.");
-                       return SPECTRE_V2_CMD_RETPOLINE;
-               } else if (match_option(arg, ret, "retpoline,amd")) {
-                       if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD) {
-                               pr_err("retpoline,amd selected but CPU is not AMD. Switching to AUTO select\n");
-                               return SPECTRE_V2_CMD_AUTO;
-                       }
-                       spec2_print_if_insecure("AMD retpoline selected on command line.");
-                       return SPECTRE_V2_CMD_RETPOLINE_AMD;
-               } else if (match_option(arg, ret, "retpoline,generic")) {
-                       spec2_print_if_insecure("generic retpoline selected on command line.");
-                       return SPECTRE_V2_CMD_RETPOLINE_GENERIC;
-               } else if (match_option(arg, ret, "auto")) {
+       int ret, i;
+       enum spectre_v2_mitigation_cmd cmd = SPECTRE_V2_CMD_AUTO;
+
+       if (cmdline_find_option_bool(boot_command_line, "nospectre_v2"))
+               return SPECTRE_V2_CMD_NONE;
+       else {
+               ret = cmdline_find_option(boot_command_line, "spectre_v2", arg,
+                                         sizeof(arg));
+               if (ret < 0)
+                       return SPECTRE_V2_CMD_AUTO;
+
+               for (i = 0; i < ARRAY_SIZE(mitigation_options); i++) {
+                       if (!match_option(arg, ret, mitigation_options[i].option))
+                               continue;
+                       cmd = mitigation_options[i].cmd;
+                       break;
+               }
+
+               if (i >= ARRAY_SIZE(mitigation_options)) {
+                       pr_err("unknown option (%s). Switching to AUTO select\n",
+                              mitigation_options[i].option);
                        return SPECTRE_V2_CMD_AUTO;
                }
        }
 
-       if (!cmdline_find_option_bool(boot_command_line, "nospectre_v2"))
+       if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||
+            cmd == SPECTRE_V2_CMD_RETPOLINE_AMD ||
+            cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC) &&
+           !IS_ENABLED(CONFIG_RETPOLINE)) {
+               pr_err("%s selected but not compiled in. Switching to AUTO select\n",
+                      mitigation_options[i].option);
                return SPECTRE_V2_CMD_AUTO;
-disable:
-       spec2_print_if_insecure("disabled on command line.");
-       return SPECTRE_V2_CMD_NONE;
+       }
+
+       if (cmd == SPECTRE_V2_CMD_RETPOLINE_AMD &&
+           boot_cpu_data.x86_vendor != X86_VENDOR_AMD) {
+               pr_err("retpoline,amd selected but CPU is not AMD. Switching to AUTO select\n");
+               return SPECTRE_V2_CMD_AUTO;
+       }
+
+       if (mitigation_options[i].secure)
+               spec2_print_if_secure(mitigation_options[i].option);
+       else
+               spec2_print_if_insecure(mitigation_options[i].option);
+
+       return cmd;
 }
 
 /* Check for Skylake-like CPUs (for RSB handling) */