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Subject[PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup function
Date
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@intel.com>
---
arch/x86/include/asm/cet.h | 1 +
arch/x86/kernel/cet.c | 26 ++++++++++++++++++++++++++
2 files changed, 27 insertions(+)

diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h
index 89330e4159a9..9e613a6598c9 100644
--- a/arch/x86/include/asm/cet.h
+++ b/arch/x86/include/asm/cet.h
@@ -31,6 +31,7 @@ void cet_disable_free_shstk(struct task_struct *p);
int cet_restore_signal(bool ia32, struct sc_ext *sc);
int cet_setup_signal(bool ia32, unsigned long rstor, struct sc_ext *sc);
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 14ad25b8ff21..e0ef996d3148 100644
--- a/arch/x86/kernel/cet.c
+++ b/arch/x86/kernel/cet.c
@@ -22,6 +22,7 @@
#include <asm/fpu/types.h>
#include <asm/cet.h>
#include <asm/special_insns.h>
+#include <asm/elf.h>
#include <uapi/asm/sigcontext.h>

static int set_shstk_ptr(unsigned long addr)
@@ -361,3 +362,28 @@ void cet_disable_ibt(void)

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.
+ */
+ modify_fpu_regs_begin();
+ rdmsrl(MSR_IA32_U_CET, r);
+ r |= (MSR_IA32_CET_LEG_IW_EN | bitmap);
+ wrmsrl(MSR_IA32_U_CET, r);
+ modify_fpu_regs_end();
+
+ return 0;
+}
--
2.17.1
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