[PATCH 4/7] x86/cet: add arcp_prctl functions for indirect branch tracking

[Yu-cheng Yu <yu-cheng.yu@intel.com>]

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
 arch/x86/include/asm/cet.h        |  1 +
 arch/x86/include/uapi/asm/prctl.h |  1 +
 arch/x86/kernel/cet_prctl.c       | 54 ++++++++++++++++++++++++++++++++++++---
 arch/x86/kernel/elf.c             | 12 ++++++---
 arch/x86/kernel/process.c         |  1 +
 5 files changed, 62 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h
index d07bdeb27db4..5b71a2b44eb1 100644
--- a/arch/x86/include/asm/cet.h
+++ b/arch/x86/include/asm/cet.h
@@ -19,6 +19,7 @@ struct cet_stat {
 	unsigned int	ibt_enabled:1;
 	unsigned int	locked:1;
 	unsigned int	exec_shstk:2;
+	unsigned int	exec_ibt:2;
 };
 
 #ifdef CONFIG_X86_INTEL_CET
diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h
index f9965403b655..fef476d2d2f6 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h
@@ -20,6 +20,7 @@
 #define ARCH_CET_EXEC		0x3004
 #define ARCH_CET_ALLOC_SHSTK	0x3005
 #define ARCH_CET_PUSH_SHSTK	0x3006
+#define ARCH_CET_LEGACY_BITMAP	0x3007
 
 /*
  * Settings for ARCH_CET_EXEC
diff --git a/arch/x86/kernel/cet_prctl.c b/arch/x86/kernel/cet_prctl.c
index 326996e2ea80..948f7ba98dc2 100644
--- a/arch/x86/kernel/cet_prctl.c
+++ b/arch/x86/kernel/cet_prctl.c
@@ -19,6 +19,7 @@
  * ARCH_CET_EXEC: set default features for exec()
  * ARCH_CET_ALLOC_SHSTK: allocate shadow stack
  * ARCH_CET_PUSH_SHSTK: put a return address on shadow stack
+ * ARCH_CET_LEGACY_BITMAP: allocate legacy bitmap
  */
 
 static int handle_get_status(unsigned long arg2)
@@ -28,8 +29,12 @@ static int handle_get_status(unsigned long arg2)
 
 	if (current->thread.cet.shstk_enabled)
 		features |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
+	if (current->thread.cet.ibt_enabled)
+		features |= GNU_PROPERTY_X86_FEATURE_1_IBT;
 	if (current->thread.cet.exec_shstk == CET_EXEC_ALWAYS_ON)
 		cet_exec |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
+	if (current->thread.cet.exec_ibt == CET_EXEC_ALWAYS_ON)
+		cet_exec |= GNU_PROPERTY_X86_FEATURE_1_IBT;
 	shstk_size = current->thread.cet.exec_shstk_size;
 
 	if (in_compat_syscall()) {
@@ -94,9 +99,18 @@ static int handle_set_exec(unsigned long arg2)
 			return -EPERM;
 	}
 
+	if (features & GNU_PROPERTY_X86_FEATURE_1_IBT) {
+		if (!cpu_feature_enabled(X86_FEATURE_IBT))
+			return -EINVAL;
+		if ((current->thread.cet.exec_ibt == CET_EXEC_ALWAYS_ON) &&
+		    (cet_exec != CET_EXEC_ALWAYS_ON))
+			return -EPERM;
+	}
+
 	if (features & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
 		current->thread.cet.exec_shstk = cet_exec;
-
+	if (features & GNU_PROPERTY_X86_FEATURE_1_IBT)
+		current->thread.cet.exec_ibt = cet_exec;
 	current->thread.cet.exec_shstk_size = shstk_size;
 	return 0;
 }
@@ -167,9 +181,36 @@ static int handle_alloc_shstk(unsigned long arg2)
 	return 0;
 }
 
+static int handle_bitmap(unsigned long arg2)
+{
+	unsigned long addr, size;
+
+	if (current->thread.cet.ibt_enabled) {
+		if (!current->thread.cet.ibt_bitmap_addr)
+			cet_setup_ibt_bitmap();
+		addr = current->thread.cet.ibt_bitmap_addr;
+		size = current->thread.cet.ibt_bitmap_size;
+	} else {
+		addr = 0;
+		size = 0;
+	}
+
+	if (in_compat_syscall()) {
+		if (put_user(addr, (unsigned int __user *)arg2) ||
+		    put_user(size, (unsigned int __user *)arg2 + 1))
+			return -EFAULT;
+	} else {
+		if (put_user(addr, (unsigned long __user *)arg2) ||
+		    put_user(size, (unsigned long __user *)arg2 + 1))
+		return -EFAULT;
+	}
+	return 0;
+}
+
 int prctl_cet(int option, unsigned long arg2)
 {
-	if (!cpu_feature_enabled(X86_FEATURE_SHSTK))
+	if (!cpu_feature_enabled(X86_FEATURE_SHSTK) &&
+	    !cpu_feature_enabled(X86_FEATURE_IBT))
 		return -EINVAL;
 
 	switch (option) {
@@ -181,7 +222,8 @@ int prctl_cet(int option, unsigned long arg2)
 			return -EPERM;
 		if (arg2 & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
 			cet_disable_free_shstk(current);
-
+		if (arg2 & GNU_PROPERTY_X86_FEATURE_1_IBT)
+			cet_disable_ibt();
 		return 0;
 
 	case ARCH_CET_LOCK:
@@ -197,6 +239,12 @@ int prctl_cet(int option, unsigned long arg2)
 	case ARCH_CET_PUSH_SHSTK:
 		return handle_push_shstk(arg2);
 
+	/*
+	 * Allocate legacy bitmap and return address & size to user.
+	 */
+	case ARCH_CET_LEGACY_BITMAP:
+		return handle_bitmap(arg2);
+
 	default:
 		return -EINVAL;
 	}
diff --git a/arch/x86/kernel/elf.c b/arch/x86/kernel/elf.c
index a3995c8c2fc2..c2a89f3c7186 100644
--- a/arch/x86/kernel/elf.c
+++ b/arch/x86/kernel/elf.c
@@ -230,10 +230,14 @@ int arch_setup_features(void *ehdr_p, void *phdr_p,
 	}
 
 	if (cpu_feature_enabled(X86_FEATURE_IBT)) {
-		if (ibt) {
-			err = cet_setup_ibt();
-			if (err < 0)
-				goto out;
+		int exec = current->thread.cet.exec_ibt;
+
+		if (exec != CET_EXEC_ALWAYS_OFF) {
+			if (ibt || (exec == CET_EXEC_ALWAYS_ON)) {
+				err = cet_setup_ibt();
+				if (err < 0)
+					goto out;
+			}
 		}
 	}
 
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 9bec164e7958..c69576b4abd1 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -801,6 +801,7 @@ long do_arch_prctl_common(struct task_struct *task, int option,
 	case ARCH_CET_EXEC:
 	case ARCH_CET_ALLOC_SHSTK:
 	case ARCH_CET_PUSH_SHSTK:
+	case ARCH_CET_LEGACY_BITMAP:
 		return prctl_cet(option, cpuid_enabled);
 	}
 
-- 
2.15.1