[PATCH v20 2/7] x86/cet/ibt: User-mode Indirect Branch Tracking support - Yu-cheng Yu

From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-mm@kvack.org, linux-arch@vger.kernel.org,
	linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Andy Lutomirski <luto@kernel.org>,
	Balbir Singh <bsingharora@gmail.com>,
	Borislav Petkov <bp@alien8.de>,
	Cyrill Gorcunov <gorcunov@gmail.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Eugene Syromiatnikov <esyr@redhat.com>,
	Florian Weimer <fweimer@redhat.com>,
	"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Kees Cook <keescook@chromium.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Nadav Amit <nadav.amit@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
	Peter Zijlstra <peterz@infradead.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Weijiang Yang <weijiang.yang@intel.com>,
	Pengfei Xu <pengfei.xu@intel.com>, <haitao.huang@intel.com>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: [PATCH v20 2/7] x86/cet/ibt: User-mode Indirect Branch Tracking support
Date: Wed, 10 Feb 2021 10:02:40 -0800	[thread overview]
Message-ID: <20210210180245.13770-3-yu-cheng.yu@intel.com> (raw)
In-Reply-To: <20210210180245.13770-1-yu-cheng.yu@intel.com>

Introduce user-mode Indirect Branch Tracking (IBT) support.  Add routines
for the setup/disable of IBT.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/include/asm/cet.h |  3 +++
 arch/x86/kernel/cet.c      | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h
index 16870e5bc8eb..3a1cba579cb2 100644
--- a/arch/x86/include/asm/cet.h
+++ b/arch/x86/include/asm/cet.h
@@ -15,6 +15,7 @@ struct cet_status {
 	unsigned long	shstk_base;
 	unsigned long	shstk_size;
 	unsigned int	locked:1;
+	unsigned int	ibt_enabled:1;
 };
 
 #ifdef CONFIG_X86_CET
@@ -26,6 +27,8 @@ void cet_free_shstk(struct task_struct *p);
 int cet_verify_rstor_token(bool ia32, unsigned long ssp, unsigned long *new_ssp);
 void cet_restore_signal(struct sc_ext *sc);
 int cet_setup_signal(bool ia32, unsigned long rstor, struct sc_ext *sc);
+int cet_setup_ibt(void);
+void cet_disable_ibt(void);
 #else
 static inline int prctl_cet(int option, u64 arg2) { return -EINVAL; }
 static inline int cet_setup_thread_shstk(struct task_struct *p,
diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
index 114f067eeb90..164139e23fef 100644
--- a/arch/x86/kernel/cet.c
+++ b/arch/x86/kernel/cet.c
@@ -13,6 +13,8 @@
 #include <linux/uaccess.h>
 #include <linux/sched/signal.h>
 #include <linux/compat.h>
+#include <linux/vmalloc.h>
+#include <linux/bitops.h>
 #include <asm/msr.h>
 #include <asm/user.h>
 #include <asm/fpu/internal.h>
@@ -341,3 +343,34 @@ int cet_setup_signal(bool ia32, unsigned long rstor_addr, struct sc_ext *sc_ext)
 
 	return 0;
 }
+
+int cet_setup_ibt(void)
+{
+	u64 msr_val;
+
+	if (!static_cpu_has(X86_FEATURE_IBT))
+		return -EOPNOTSUPP;
+
+	start_update_msrs();
+	rdmsrl(MSR_IA32_U_CET, msr_val);
+	msr_val |= (CET_ENDBR_EN | CET_NO_TRACK_EN);
+	wrmsrl(MSR_IA32_U_CET, msr_val);
+	end_update_msrs();
+	current->thread.cet.ibt_enabled = 1;
+	return 0;
+}
+
+void cet_disable_ibt(void)
+{
+	u64 msr_val;
+
+	if (!static_cpu_has(X86_FEATURE_IBT))
+		return;
+
+	start_update_msrs();
+	rdmsrl(MSR_IA32_U_CET, msr_val);
+	msr_val &= ~CET_ENDBR_EN;
+	wrmsrl(MSR_IA32_U_CET, msr_val);
+	end_update_msrs();
+	current->thread.cet.ibt_enabled = 0;
+}
-- 
2.21.0

