Indirect Branch Tracking (IBT) provides an optional legacy code bitmap
that allows execution of legacy, non-IBT compatible library by an
IBT-enabled application. When set, each bit in the bitmap indicates
one page of legacy code.
The bitmap is allocated and setup from the application.
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
---
arch/x86/include/asm/cet.h | 1 +
arch/x86/kernel/cet.c | 23 +++++++++++++++++++++++
2 files changed, 24 insertions(+)
diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h
index 810d3e386fdb..db40fc54a905 100644
--- a/arch/x86/include/asm/cet.h
+++ b/arch/x86/include/asm/cet.h
@@ -29,6 +29,7 @@ void cet_disable_free_shstk(struct task_struct *p);
int cet_restore_signal(unsigned long ssp);
int cet_setup_signal(bool ia32, unsigned long rstor, unsigned long *new_ssp);
int cet_setup_ibt(void);
+int cet_setup_ibt_bitmap(unsigned long bitmap, unsigned long size);
void cet_disable_ibt(void);
#else
static inline int prctl_cet(int option, unsigned long arg2) { return -EINVAL; }
diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
index fd157a6208c3..18a92a92c50f 100644
--- a/arch/x86/kernel/cet.c
+++ b/arch/x86/kernel/cet.c
@@ -21,6 +21,7 @@
#include <asm/fpu/types.h>
#include <asm/cet.h>
#include <asm/special_insns.h>
+#include <asm/elf.h>
static int set_shstk_ptr(unsigned long addr)
{
@@ -333,3 +334,25 @@ void cet_disable_ibt(void)
wrmsrl(MSR_IA32_U_CET, r);
current->thread.cet.ibt_enabled = 0;
}
+
+int cet_setup_ibt_bitmap(unsigned long bitmap, unsigned long size)
+{
+ u64 r;
+
+ if (!current->thread.cet.ibt_enabled)
+ return -EINVAL;
+
+ if (!PAGE_ALIGNED(bitmap) || (size > TASK_SIZE_MAX))
+ return -EINVAL;
+
+ current->thread.cet.ibt_bitmap_addr = bitmap;
+ current->thread.cet.ibt_bitmap_size = size;
+
+ /*
+ * Turn on IBT legacy bitmap.
+ */
+ rdmsrl(MSR_IA32_U_CET, r);
+ r |= (MSR_IA32_CET_LEG_IW_EN | bitmap);
+ wrmsrl(MSR_IA32_U_CET, r);
+ return 0;
+}
--
2.17.1
