[PATCH v23 2/9] x86/cet/ibt: User-mode Indirect Branch Tracking support
From: Yu-cheng Yu <hidden>
Date: 2021-03-16 15:18:23
Also in:
linux-api, linux-doc, linux-mm, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Introduce user-mode Indirect Branch Tracking (IBT) support. Add routines for the setup/disable of IBT. Signed-off-by: Yu-cheng Yu <redacted> Reviewed-by: Kees Cook <redacted> --- 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 c2437378f339..c20c2f671145 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
@@ -27,6 +28,8 @@ 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 12738cdfb5f2..3361706ba950 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>
@@ -346,3 +348,34 @@ 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