Introduce user-mode Indirect Branch Tracking (IBT) support. Update setup
routines to include IBT.
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
---
arch/x86/include/asm/cet.h | 3 +++
arch/x86/include/asm/disabled-features.h | 8 +++++-
arch/x86/kernel/cet.c | 33 ++++++++++++++++++++++++
arch/x86/kernel/cpu/common.c | 17 ++++++++++++
4 files changed, 60 insertions(+), 1 deletion(-)
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/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index 6a9fb7f9bc01..e634a03fee14 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -68,6 +68,12 @@
#define DISABLE_SHSTK (1 << (X86_FEATURE_SHSTK & 31))
#endif
+#ifdef CONFIG_X86_BRANCH_TRACKING_USER
+#define DISABLE_IBT 0
+#else
+#define DISABLE_IBT (1<<(X86_FEATURE_IBT & 31))
+#endif
+
/*
* Make sure to add features to the correct mask
*/
@@ -90,7 +96,7 @@
#define DISABLED_MASK16 (DISABLE_PKU|DISABLE_OSPKE|DISABLE_LA57|DISABLE_UMIP| \
DISABLE_ENQCMD|DISABLE_SHSTK)
#define DISABLED_MASK17 0
-#define DISABLED_MASK18 0
+#define DISABLED_MASK18 (DISABLE_IBT)
#define DISABLED_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != 19)
#endif /* _ASM_X86_DISABLED_FEATURES_H */
diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
index d57f3a433af9..1dcd16aa4f90 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_SHSTK_EN;
+ wrmsrl(MSR_IA32_U_CET, msr_val);
+ end_update_msrs();
+ current->thread.cet.ibt_enabled = 0;
+}
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 3d38ae02d9d3..496d25e1c0a1 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -537,6 +537,23 @@ static __init int setup_disable_shstk(char *s)
__setup("no_user_shstk", setup_disable_shstk);
#endif
+#ifdef CONFIG_X86_BRANCH_TRACKING_USER
+static __init int setup_disable_ibt(char *s)
+{
+ /* require an exact match without trailing characters */
+ if (s[0] != '\0')
+ return 0;
+
+ if (!boot_cpu_has(X86_FEATURE_IBT))
+ return 1;
+
+ setup_clear_cpu_cap(X86_FEATURE_IBT);
+ pr_info("x86: 'no_user_ibt' specified, disabling user Branch Tracking\n");
+ return 1;
+}
+__setup("no_user_ibt", setup_disable_ibt);
+#endif
+
/*
* Some CPU features depend on higher CPUID levels, which may not always
* be available due to CPUID level capping or broken virtualization
--
2.21.0
