[PATCH 2/7] x86/cet: User-mode indirect branch tracking support
From: Yu-cheng Yu
Date: Thu Jun 07 2018 - 10:42:38 EST
Add user-mode indirect branch tracking enabling/disabling
and supporting routines.
Signed-off-by: H.J. Lu <hjl.tools@xxxxxxxxx>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
---
arch/x86/include/asm/cet.h | 8 ++++
arch/x86/include/asm/disabled-features.h | 8 +++-
arch/x86/kernel/cet.c | 73 ++++++++++++++++++++++++++++++++
arch/x86/kernel/cpu/common.c | 20 ++++++++-
arch/x86/kernel/elf.c | 15 ++++++-
arch/x86/kernel/process.c | 1 +
6 files changed, 122 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h
index a2a53fe4d5e6..d07bdeb27db4 100644
--- a/arch/x86/include/asm/cet.h
+++ b/arch/x86/include/asm/cet.h
@@ -13,7 +13,10 @@ struct cet_stat {
unsigned long shstk_base;
unsigned long shstk_size;
unsigned long exec_shstk_size;
+ unsigned long ibt_bitmap_addr;
+ unsigned long ibt_bitmap_size;
unsigned int shstk_enabled:1;
+ unsigned int ibt_enabled:1;
unsigned int locked:1;
unsigned int exec_shstk:2;
};
@@ -29,6 +32,9 @@ void cet_disable_shstk(void);
void cet_disable_free_shstk(struct task_struct *p);
int cet_restore_signal(unsigned long ssp);
int cet_setup_signal(int ia32, unsigned long addr);
+int cet_setup_ibt(void);
+int cet_setup_ibt_bitmap(void);
+void cet_disable_ibt(void);
#else
static inline int prctl_cet(int option, unsigned long arg2) { return 0; }
static inline unsigned long cet_get_shstk_ptr(void) { return 0; }
@@ -41,6 +47,8 @@ static inline void cet_disable_shstk(void) {}
static inline void cet_disable_free_shstk(struct task_struct *p) {}
static inline int cet_restore_signal(unsigned long ssp) { return 0; }
static inline int cet_setup_signal(int ia32, unsigned long addr) { return 0; }
+static inline int cet_setup_ibt(void) { return 0; }
+static inline void cet_disable_ibt(void) {}
#endif
#endif /* __ASSEMBLY__ */
diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index 3624a11e5ba6..ce5bdaf0f1ff 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -62,6 +62,12 @@
#define DISABLE_SHSTK (1<<(X86_FEATURE_SHSTK & 31))
#endif
+#ifdef CONFIG_X86_INTEL_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
*/
@@ -72,7 +78,7 @@
#define DISABLED_MASK4 (DISABLE_PCID)
#define DISABLED_MASK5 0
#define DISABLED_MASK6 0
-#define DISABLED_MASK7 (DISABLE_PTI)
+#define DISABLED_MASK7 (DISABLE_PTI|DISABLE_IBT)
#define DISABLED_MASK8 0
#define DISABLED_MASK9 (DISABLE_MPX)
#define DISABLED_MASK10 0
diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
index 1b7089dcf1ea..4df4b583311f 100644
--- a/arch/x86/kernel/cet.c
+++ b/arch/x86/kernel/cet.c
@@ -12,6 +12,8 @@
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/sched/signal.h>
+#include <linux/vmalloc.h>
+#include <linux/bitops.h>
#include <asm/msr.h>
#include <asm/user.h>
#include <asm/fpu/xstate.h>
@@ -222,3 +224,74 @@ int cet_setup_signal(int ia32, unsigned long rstor_addr)
return cet_push_shstk(ia32, ssp, rstor_addr);
}
+
+static unsigned long ibt_mmap(unsigned long addr, unsigned long len)
+{
+ struct mm_struct *mm = current->mm;
+ unsigned long populate;
+
+ down_write(&mm->mmap_sem);
+ addr = do_mmap(NULL, addr, len, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE,
+ VM_DONTDUMP, 0, &populate, NULL);
+ up_write(&mm->mmap_sem);
+
+ if (populate)
+ mm_populate(addr, populate);
+
+ return addr;
+}
+
+int cet_setup_ibt(void)
+{
+ u64 r;
+
+ if (!cpu_feature_enabled(X86_FEATURE_IBT))
+ return -EOPNOTSUPP;
+
+ rdmsrl(MSR_IA32_U_CET, r);
+ r |= (MSR_IA32_CET_ENDBR_EN | MSR_IA32_CET_NO_TRACK_EN);
+ wrmsrl(MSR_IA32_U_CET, r);
+ current->thread.cet.ibt_enabled = 1;
+ return 0;
+}
+
+int cet_setup_ibt_bitmap(void)
+{
+ u64 r;
+ unsigned long bitmap;
+ unsigned long size;
+
+ if (!cpu_feature_enabled(X86_FEATURE_IBT))
+ return -EOPNOTSUPP;
+
+ size = TASK_SIZE / PAGE_SIZE / BITS_PER_BYTE;
+ bitmap = ibt_mmap(0, size);
+
+ if (bitmap >= TASK_SIZE)
+ return -ENOMEM;
+
+ bitmap &= PAGE_MASK;
+
+ rdmsrl(MSR_IA32_U_CET, r);
+ r |= (MSR_IA32_CET_LEG_IW_EN | bitmap);
+ wrmsrl(MSR_IA32_U_CET, r);
+
+ current->thread.cet.ibt_bitmap_addr = bitmap;
+ current->thread.cet.ibt_bitmap_size = size;
+ return 0;
+}
+
+void cet_disable_ibt(void)
+{
+ u64 r;
+
+ if (!cpu_feature_enabled(X86_FEATURE_IBT))
+ return;
+
+ rdmsrl(MSR_IA32_U_CET, r);
+ r &= ~(MSR_IA32_CET_ENDBR_EN | MSR_IA32_CET_LEG_IW_EN |
+ MSR_IA32_CET_NO_TRACK_EN);
+ wrmsrl(MSR_IA32_U_CET, r);
+ current->thread.cet.ibt_enabled = 0;
+}
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index f54fabdaef60..4041d6b94455 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -403,7 +403,8 @@ __setup("nopku", setup_disable_pku);
static __always_inline void setup_cet(struct cpuinfo_x86 *c)
{
- if (cpu_feature_enabled(X86_FEATURE_SHSTK))
+ if (cpu_feature_enabled(X86_FEATURE_SHSTK) ||
+ cpu_feature_enabled(X86_FEATURE_IBT))
cr4_set_bits(X86_CR4_CET);
}
@@ -424,6 +425,23 @@ static __init int setup_disable_shstk(char *s)
__setup("noshstk", setup_disable_shstk);
#endif
+#ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER
+static __init int setup_disable_ibt(char *s)
+{
+ /* require an exact match without trailing characters */
+ if (strlen(s))
+ return 0;
+
+ if (!boot_cpu_has(X86_FEATURE_IBT))
+ return 1;
+
+ setup_clear_cpu_cap(X86_FEATURE_IBT);
+ pr_info("x86: 'noibt' specified, disabling Branch Tracking\n");
+ return 1;
+}
+__setup("noibt", 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
diff --git a/arch/x86/kernel/elf.c b/arch/x86/kernel/elf.c
index de08d41971f6..a3995c8c2fc2 100644
--- a/arch/x86/kernel/elf.c
+++ b/arch/x86/kernel/elf.c
@@ -18,6 +18,7 @@
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/string.h>
+#include <linux/compat.h>
#define ELF_NOTE_DESC_OFFSET(n, align) \
round_up(sizeof(*n) + n->n_namesz, (align))
@@ -183,7 +184,8 @@ int arch_setup_features(void *ehdr_p, void *phdr_p,
struct elf64_hdr *ehdr64 = ehdr_p;
- if (!cpu_feature_enabled(X86_FEATURE_SHSTK))
+ if (!cpu_feature_enabled(X86_FEATURE_SHSTK) &&
+ !cpu_feature_enabled(X86_FEATURE_IBT))
return 0;
if (ehdr64->e_ident[EI_CLASS] == ELFCLASS64) {
@@ -211,6 +213,9 @@ int arch_setup_features(void *ehdr_p, void *phdr_p,
current->thread.cet.shstk_enabled = 0;
current->thread.cet.shstk_base = 0;
current->thread.cet.shstk_size = 0;
+ current->thread.cet.ibt_enabled = 0;
+ current->thread.cet.ibt_bitmap_addr = 0;
+ current->thread.cet.ibt_bitmap_size = 0;
current->thread.cet.locked = 0;
if (cpu_feature_enabled(X86_FEATURE_SHSTK)) {
int exec = current->thread.cet.exec_shstk;
@@ -224,6 +229,14 @@ 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;
+ }
+ }
+
/*
* Lockout CET features if no interpreter
*/
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 54ad1863c6d2..9bec164e7958 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -139,6 +139,7 @@ void flush_thread(void)
memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
cet_disable_shstk();
+ cet_disable_ibt();
fpu__clear(&tsk->thread.fpu);
}
--
2.15.1