[PATCH v5 06/11] x86/cet/ibt: Add arch_prctl functions for IBT

[Yu-cheng Yu]

Update ARCH_X86_CET_STATUS and ARCH_X86_CET_DISABLE to include
Indirect Branch Tracking features.

Introduce:

arch_prctl(ARCH_X86_CET_GET_LEGACY_BITMAP, unsigned long *addr)
    Enable the Indirect Branch Tracking legacy code bitmap.
    Allocate the bitmap if the task does not have one.

    The parameter 'addr' is a pointer to a user buffer.
    On returning to the caller, the kernel fills the following:

    *addr = IBT bitmap base address
    *(addr + 1) = IBT bitmap size

Signed-off-by: H.J. Lu <hjl.to...@gmail.com>
Signed-off-by: Yu-cheng Yu <yu-cheng...@intel.com>
---
 arch/x86/include/uapi/asm/prctl.h |  1 +
 arch/x86/kernel/cet_prctl.c       | 35 +++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/arch/x86/include/uapi/asm/prctl.h 
b/arch/x86/include/uapi/asm/prctl.h
index d962f0ec9ccf..fd4eae92c733 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h
@@ -18,5 +18,6 @@
 #define ARCH_X86_CET_DISABLE           0x3002
 #define ARCH_X86_CET_LOCK              0x3003
 #define ARCH_X86_CET_ALLOC_SHSTK       0x3004
+#define ARCH_X86_CET_GET_LEGACY_BITMAP 0x3005
 
 #endif /* _ASM_X86_PRCTL_H */
diff --git a/arch/x86/kernel/cet_prctl.c b/arch/x86/kernel/cet_prctl.c
index 320dbb620d61..dc7e9785f5e7 100644
--- a/arch/x86/kernel/cet_prctl.c
+++ b/arch/x86/kernel/cet_prctl.c
@@ -21,6 +21,8 @@ static int handle_get_status(unsigned long arg2)
 
        if (current->thread.cet.shstk_enabled)
                features |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
+       if (current->thread.cet.ibt_enabled)
+               features |= GNU_PROPERTY_X86_FEATURE_1_IBT;
 
        shstk_base = current->thread.cet.shstk_base;
        shstk_size = current->thread.cet.shstk_size;
@@ -56,6 +58,31 @@ static int handle_alloc_shstk(unsigned long arg2)
        return 0;
 }
 
+static int handle_bitmap(unsigned long arg2)
+{
+       unsigned long addr, size;
+
+       if (current->thread.cet.ibt_enabled) {
+               int err;
+
+               err  = cet_setup_ibt_bitmap();
+               if (err)
+                       return err;
+
+               addr = current->thread.cet.ibt_bitmap_addr;
+               size = current->thread.cet.ibt_bitmap_size;
+       } else {
+               addr = 0;
+               size = 0;
+       }
+
+       if (put_user(addr, (unsigned long __user *)arg2) ||
+           put_user(size, (unsigned long __user *)arg2 + 1))
+               return -EFAULT;
+
+       return 0;
+}
+
 int prctl_cet(int option, unsigned long arg2)
 {
        if (!cpu_x86_cet_enabled())
@@ -70,6 +97,8 @@ int prctl_cet(int option, unsigned long arg2)
                        return -EPERM;
                if (arg2 & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
                        cet_disable_free_shstk(current);
+               if (arg2 & GNU_PROPERTY_X86_FEATURE_1_IBT)
+                       cet_disable_ibt();
 
                return 0;
 
@@ -80,6 +109,12 @@ int prctl_cet(int option, unsigned long arg2)
        case ARCH_X86_CET_ALLOC_SHSTK:
                return handle_alloc_shstk(arg2);
 
+       /*
+        * Allocate legacy bitmap and return address & size to user.
+        */
+       case ARCH_X86_CET_GET_LEGACY_BITMAP:
+               return handle_bitmap(arg2);
+
        default:
                return -EINVAL;
        }
-- 
2.17.1