x86/traps: Move control protection handler to separate file

Today the control protection handler is defined in traps.c and used only for the kernel IBT feature. To reduce ifdeffery, move it to it's own file. In future patches, functionality will be added to make this handler also handle user shadow stack faults. So name the file cet.c. No functional change. Signed-off-by: Rick Edgecombe <[email protected]> Signed-off-by: Dave Hansen <[email protected]> Reviewed-by: Borislav Petkov (AMD) <[email protected]> Reviewed-by: Kees Cook <[email protected]> Acked-by: Mike Rapoport (IBM) <[email protected]> Tested-by: Pengfei Xu <[email protected]> Tested-by: John Allen <[email protected]> Tested-by: Kees Cook <[email protected]> Link: https://lore.kernel.org/all/20230613001108.3040476-8-rick.p.edgecombe%40intel.com
niw · Jul 11, 2023 · 2da5b91 · 2da5b91
1 parent 18e66b6
commit 2da5b91
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Showing 3 changed files with 78 additions and 75 deletions.
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
@@ -145,6 +145,8 @@ obj-$(CONFIG_CFI_CLANG)			+= cfi.o
 
 obj-$(CONFIG_CALL_THUNKS)		+= callthunks.o
 
+obj-$(CONFIG_X86_CET)			+= cet.o
+
 ###
 # 64 bit specific files
 ifeq ($(CONFIG_X86_64),y)

diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/ptrace.h>
+#include <asm/bugs.h>
+#include <asm/traps.h>
+
+static __ro_after_init bool ibt_fatal = true;
+
+extern void ibt_selftest_ip(void); /* code label defined in asm below */
+
+enum cp_error_code {
+	CP_EC        = (1 << 15) - 1,
+
+	CP_RET       = 1,
+	CP_IRET      = 2,
+	CP_ENDBR     = 3,
+	CP_RSTRORSSP = 4,
+	CP_SETSSBSY  = 5,
+
+	CP_ENCL	     = 1 << 15,
+};
+
+DEFINE_IDTENTRY_ERRORCODE(exc_control_protection)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_IBT)) {
+		pr_err("Unexpected #CP\n");
+		BUG();
+	}
+
+	if (WARN_ON_ONCE(user_mode(regs) || (error_code & CP_EC) != CP_ENDBR))
+		return;
+
+	if (unlikely(regs->ip == (unsigned long)&ibt_selftest_ip)) {
+		regs->ax = 0;
+		return;
+	}
+
+	pr_err("Missing ENDBR: %pS\n", (void *)instruction_pointer(regs));
+	if (!ibt_fatal) {
+		printk(KERN_DEFAULT CUT_HERE);
+		__warn(__FILE__, __LINE__, (void *)regs->ip, TAINT_WARN, regs, NULL);
+		return;
+	}
+	BUG();
+}
+
+/* Must be noinline to ensure uniqueness of ibt_selftest_ip. */
+noinline bool ibt_selftest(void)
+{
+	unsigned long ret;
+
+	asm ("	lea ibt_selftest_ip(%%rip), %%rax\n\t"
+	     ANNOTATE_RETPOLINE_SAFE
+	     "	jmp *%%rax\n\t"
+	     "ibt_selftest_ip:\n\t"
+	     UNWIND_HINT_FUNC
+	     ANNOTATE_NOENDBR
+	     "	nop\n\t"
+
+	     : "=a" (ret) : : "memory");
+
+	return !ret;
+}
+
+static int __init ibt_setup(char *str)
+{
+	if (!strcmp(str, "off"))
+		setup_clear_cpu_cap(X86_FEATURE_IBT);
+
+	if (!strcmp(str, "warn"))
+		ibt_fatal = false;
+
+	return 1;
+}
+
+__setup("ibt=", ibt_setup);
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
@@ -213,81 +213,6 @@ DEFINE_IDTENTRY(exc_overflow)
 	do_error_trap(regs, 0, "overflow", X86_TRAP_OF, SIGSEGV, 0, NULL);
 }
 
-#ifdef CONFIG_X86_KERNEL_IBT
-
-static __ro_after_init bool ibt_fatal = true;
-
-extern void ibt_selftest_ip(void); /* code label defined in asm below */
-
-enum cp_error_code {
-	CP_EC        = (1 << 15) - 1,
-
-	CP_RET       = 1,
-	CP_IRET      = 2,
-	CP_ENDBR     = 3,
-	CP_RSTRORSSP = 4,
-	CP_SETSSBSY  = 5,
-
-	CP_ENCL	     = 1 << 15,
-};
-
-DEFINE_IDTENTRY_ERRORCODE(exc_control_protection)
-{
-	if (!cpu_feature_enabled(X86_FEATURE_IBT)) {
-		pr_err("Unexpected #CP\n");
-		BUG();
-	}
-
-	if (WARN_ON_ONCE(user_mode(regs) || (error_code & CP_EC) != CP_ENDBR))
-		return;
-
-	if (unlikely(regs->ip == (unsigned long)&ibt_selftest_ip)) {
-		regs->ax = 0;
-		return;
-	}
-
-	pr_err("Missing ENDBR: %pS\n", (void *)instruction_pointer(regs));
-	if (!ibt_fatal) {
-		printk(KERN_DEFAULT CUT_HERE);
-		__warn(__FILE__, __LINE__, (void *)regs->ip, TAINT_WARN, regs, NULL);
-		return;
-	}
-	BUG();
-}
-
-/* Must be noinline to ensure uniqueness of ibt_selftest_ip. */
-noinline bool ibt_selftest(void)
-{
-	unsigned long ret;
-
-	asm ("	lea ibt_selftest_ip(%%rip), %%rax\n\t"
-	     ANNOTATE_RETPOLINE_SAFE
-	     "	jmp *%%rax\n\t"
-	     "ibt_selftest_ip:\n\t"
-	     UNWIND_HINT_FUNC
-	     ANNOTATE_NOENDBR
-	     "	nop\n\t"
-
-	     : "=a" (ret) : : "memory");
-
-	return !ret;
-}
-
-static int __init ibt_setup(char *str)
-{
-	if (!strcmp(str, "off"))
-		setup_clear_cpu_cap(X86_FEATURE_IBT);
-
-	if (!strcmp(str, "warn"))
-		ibt_fatal = false;
-
-	return 1;
-}
-
-__setup("ibt=", ibt_setup);
-
-#endif /* CONFIG_X86_KERNEL_IBT */
-
 #ifdef CONFIG_X86_F00F_BUG
 void handle_invalid_op(struct pt_regs *regs)
 #else