Re: [RFC PATCH v2 27/27] x86/cet: Add arch_prctl functions for CET

diff --git a/arch/x86/kernel/cet_prctl.c b/arch/x86/kernel/cet_prctl.c
new file mode 100644
index 000000000000..86bb78ae656d
--- /dev/null
+++ b/arch/x86/kernel/cet_prctl.c

@@ -0,0 +1,141 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/errno.h>
+#include <linux/uaccess.h>
+#include <linux/prctl.h>
+#include <linux/compat.h>
+#include <asm/processor.h>
+#include <asm/prctl.h>
+#include <asm/elf.h>
+#include <asm/elf_property.h>
+#include <asm/cet.h>
+
+/* See Documentation/x86/intel_cet.txt. */
+
+static int handle_get_status(unsigned long arg2)
+{
+       unsigned int features = 0;
+       unsigned long shstk_base, shstk_size;
+
+       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;
+
+       if (in_ia32_syscall()) {
+               unsigned int buf[3];
+
+               buf[0] = features;
+               buf[1] = (unsigned int)shstk_base;
+               buf[2] = (unsigned int)shstk_size;
+               return copy_to_user((unsigned int __user *)arg2, buf,
+                                   sizeof(buf));
+       } else {
+               unsigned long buf[3];
+
+               buf[0] = (unsigned long)features;
+               buf[1] = shstk_base;
+               buf[2] = shstk_size;
+               return copy_to_user((unsigned long __user *)arg2, buf,
+                                   sizeof(buf));
+       }

+}
+
+static int handle_alloc_shstk(unsigned long arg2)
+{
+       int err = 0;
+       unsigned long shstk_size = 0;
+
+       if (in_ia32_syscall()) {
+               unsigned int size;
+
+               err = get_user(size, (unsigned int __user *)arg2);
+               if (!err)
+                       shstk_size = size;
+       } else {
+               err = get_user(shstk_size, (unsigned long __user *)arg2);
+       }

+       if (err)
+               return -EFAULT;
+
+       err = cet_alloc_shstk(&shstk_size);
+       if (err)
+               return -err;
+
+       if (in_ia32_syscall()) {
+               if (put_user(shstk_size, (unsigned int __user *)arg2))
+                       return -EFAULT;
+       } else {
+               if (put_user(shstk_size, (unsigned long __user *)arg2))
+                       return -EFAULT;
+       }
+       return 0;
+}
+
+static int handle_bitmap(unsigned long arg2)
+{
+       unsigned long addr, size;
+
+       if (current->thread.cet.ibt_enabled) {
+               if (!current->thread.cet.ibt_bitmap_addr)
+                       cet_setup_ibt_bitmap();
+               addr = current->thread.cet.ibt_bitmap_addr;
+               size = current->thread.cet.ibt_bitmap_size;
+       } else {
+               addr = 0;
+               size = 0;
+       }
+
+       if (in_compat_syscall()) {
+               if (put_user(addr, (unsigned int __user *)arg2) ||
+                   put_user(size, (unsigned int __user *)arg2 + 1))
+                       return -EFAULT;
+       } else {
+               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_feature_enabled(X86_FEATURE_SHSTK) &&
+           !cpu_feature_enabled(X86_FEATURE_IBT))
+               return -EINVAL;
+
+       switch (option) {
+       case ARCH_CET_STATUS:
+               return handle_get_status(arg2);
+
+       case ARCH_CET_DISABLE:
+               if (current->thread.cet.locked)
+                       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;
+
+       case ARCH_CET_LOCK:
+               current->thread.cet.locked = 1;
+               return 0;
+
+       case ARCH_CET_ALLOC_SHSTK:
+               return handle_alloc_shstk(arg2);
+
+       /*
+        * Allocate legacy bitmap and return address & size to user.
+        */
+       case ARCH_CET_LEGACY_BITMAP:
+               return handle_bitmap(arg2);
+
+       default:
+               return -EINVAL;
+       }
+}

diff --git a/arch/x86/kernel/elf.c b/arch/x86/kernel/elf.c
index 42e08d3b573e..3d4934fdac7f 100644
--- a/arch/x86/kernel/elf.c
+++ b/arch/x86/kernel/elf.c

@@ -8,7 +8,10 @@

 #include <asm/cet.h>
 #include <asm/elf_property.h>
+#include <asm/prctl.h>
+#include <asm/processor.h>
 #include <uapi/linux/elf-em.h>
+#include <uapi/linux/prctl.h>
 #include <linux/binfmts.h>
 #include <linux/elf.h>
 #include <linux/slab.h>

@@ -255,6 +258,7 @@ int arch_setup_features(void *ehdr_p, void *phdr_p,
        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)) {
                if (shstk) {
                        err = cet_setup_shstk();

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 43a57d284a22..259b92664981 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c

@@ -795,6 +795,12 @@ long do_arch_prctl_common(struct task_struct *task, int option,
                return get_cpuid_mode();
        case ARCH_SET_CPUID:
                return set_cpuid_mode(task, cpuid_enabled);
+       case ARCH_CET_STATUS:
+       case ARCH_CET_DISABLE:
+       case ARCH_CET_LOCK:
+       case ARCH_CET_ALLOC_SHSTK:
+       case ARCH_CET_LEGACY_BITMAP:
+               return prctl_cet(option, cpuid_enabled);
        }

        return -EINVAL;
--

2.17.1