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Subject[PATCH v2 3/4] x86, mpx: add prctl commands PR_MPX_INIT, PR_MPX_RELEASE
Date
This patch adds the PR_MPX_INIT and PR_MPX_RELEASE prctl()
commands on the x86 platform. These commands can be used to
init and release MPX related resource.

A MMU notifier will be registered during PR_MPX_INIT
command execution. So the bound tables can be automatically
deallocated when one memory area is unmapped.

Signed-off-by: Qiaowei Ren <qiaowei.ren@intel.com>
---
arch/x86/Kconfig | 4 ++
arch/x86/include/asm/mpx.h | 9 ++++
arch/x86/include/asm/processor.h | 16 +++++++
arch/x86/kernel/mpx.c | 84 ++++++++++++++++++++++++++++++++++++++
include/uapi/linux/prctl.h | 6 +++
kernel/sys.c | 12 +++++
6 files changed, 131 insertions(+), 0 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ee2fb9d..695101a 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -233,6 +233,10 @@ config HAVE_INTEL_TXT
def_bool y
depends on INTEL_IOMMU && ACPI

+config HAVE_INTEL_MPX
+ def_bool y
+ select MMU_NOTIFIER
+
config X86_32_SMP
def_bool y
depends on X86_32 && SMP
diff --git a/arch/x86/include/asm/mpx.h b/arch/x86/include/asm/mpx.h
index d074153..9652e9e 100644
--- a/arch/x86/include/asm/mpx.h
+++ b/arch/x86/include/asm/mpx.h
@@ -30,6 +30,15 @@

#endif

+typedef union {
+ struct {
+ unsigned long ignored:MPX_IGN_BITS;
+ unsigned long l2index:MPX_L2_BITS;
+ unsigned long l1index:MPX_L1_BITS;
+ };
+ unsigned long addr;
+} mpx_addr;
+
void do_mpx_bt_fault(struct xsave_struct *xsave_buf);

#endif /* _ASM_X86_MPX_H */
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 43be6f6..ea4e72d 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -963,6 +963,22 @@ extern void start_thread(struct pt_regs *regs, unsigned long new_ip,
extern int get_tsc_mode(unsigned long adr);
extern int set_tsc_mode(unsigned int val);

+#ifdef CONFIG_HAVE_INTEL_MPX
+
+/* Init/release a process' MPX related resource */
+#define MPX_INIT(tsk) mpx_init((tsk))
+#define MPX_RELEASE(tsk) mpx_release((tsk))
+
+extern int mpx_init(struct task_struct *tsk);
+extern int mpx_release(struct task_struct *tsk);
+
+#else /* CONFIG_HAVE_INTEL_MPX */
+
+#define MPX_INIT(tsk) (-EINVAL)
+#define MPX_RELEASE(tsk) (-EINVAL)
+
+#endif /* CONFIG_HAVE_INTEL_MPX */
+
extern u16 amd_get_nb_id(int cpu);

static inline uint32_t hypervisor_cpuid_base(const char *sig, uint32_t leaves)
diff --git a/arch/x86/kernel/mpx.c b/arch/x86/kernel/mpx.c
index 767b3bf..ffe5aee 100644
--- a/arch/x86/kernel/mpx.c
+++ b/arch/x86/kernel/mpx.c
@@ -1,5 +1,7 @@
#include <linux/kernel.h>
#include <linux/syscalls.h>
+#include <linux/prctl.h>
+#include <linux/mmu_notifier.h>
#include <asm/processor.h>
#include <asm/mpx.h>
#include <asm/mman.h>
@@ -7,6 +9,88 @@
#include <asm/fpu-internal.h>
#include <asm/alternative.h>

+static struct mmu_notifier mpx_mn;
+
+static void mpx_invl_range_end(struct mmu_notifier *mn,
+ struct mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+ struct xsave_struct *xsave_buf;
+ unsigned long bt_size = 1UL << (MPX_L2_BITS+MPX_L2_SHIFT);
+ unsigned long bt_addr;
+ unsigned long bd_base;
+ unsigned long bd_entry, bde_start, bde_end;
+ mpx_addr lap;
+
+ pgd_t *pgd;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ /* ignore swap notifications */
+ pgd = pgd_offset(mm, start);
+ pud = pud_offset(pgd, start);
+ pmd = pmd_offset(pud, start);
+ pte = pte_offset_kernel(pmd, start);
+ if (!pte_present(*pte) && !pte_none(*pte) && !pte_file(*pte))
+ return;
+
+ /* get bound directory base address */
+ fpu_xsave(&current->thread.fpu);
+ xsave_buf = &(current->thread.fpu.state->xsave);
+ bd_base = xsave_buf->bndcsr.cfg_reg_u & MPX_BNDCFG_ADDR_MASK;
+
+ /* get related bde range */
+ lap.addr = start;
+ bde_start = bd_base + (lap.l1index << MPX_L1_SHIFT);
+
+ lap.addr = end;
+ if (lap.ignored || lap.l2index)
+ bde_end = bd_base + (lap.l1index<<MPX_L1_SHIFT) + sizeof(long);
+ else
+ bde_end = bd_base + (lap.l1index<<MPX_L1_SHIFT);
+
+ for (bd_entry = bde_start; bd_entry < bde_end;
+ bd_entry += sizeof(unsigned long)) {
+
+ if (get_user(bt_addr, (long __user *)bd_entry))
+ return;
+
+ if (bt_addr & 0x1) {
+ user_atomic_cmpxchg_inatomic(&bt_addr,
+ (long __user *)bd_entry, bt_addr, 0);
+ do_munmap(mm, bt_addr & MPX_L2_NODE_ADDR_MASK, bt_size);
+ }
+ }
+}
+
+static struct mmu_notifier_ops mpx_mmuops = {
+ .invalidate_range_end = mpx_invl_range_end,
+};
+
+int mpx_init(struct task_struct *tsk)
+{
+ if (!boot_cpu_has(X86_FEATURE_MPX))
+ return -EINVAL;
+
+ /* register mmu_notifier to delallocate the bound tables */
+ mpx_mn.ops = &mpx_mmuops;
+ mmu_notifier_register(&mpx_mn, current->mm);
+
+ return 0;
+}
+
+int mpx_release(struct task_struct *tsk)
+{
+ if (!boot_cpu_has(X86_FEATURE_MPX))
+ return -EINVAL;
+
+ /* unregister mmu_notifier */
+ mmu_notifier_unregister(&mpx_mn, current->mm);
+
+ return 0;
+}
+
static bool allocate_bt(unsigned long bd_entry)
{
unsigned long bt_size = 1UL << (MPX_L2_BITS+MPX_L2_SHIFT);
diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 289760f..19ab881 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -149,4 +149,10 @@

#define PR_GET_TID_ADDRESS 40

+/*
+ * Init/release MPX related resource.
+ */
+#define PR_MPX_INIT 41
+#define PR_MPX_RELEASE 42
+
#endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index c18ecca..bbaf573 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -92,6 +92,12 @@
#ifndef SET_TSC_CTL
# define SET_TSC_CTL(a) (-EINVAL)
#endif
+#ifndef MPX_INIT
+# define MPX_INIT(a) (-EINVAL)
+#endif
+#ifndef MPX_RELEASE
+# define MPX_RELEASE(a) (-EINVAL)
+#endif

/*
* this is where the system-wide overflow UID and GID are defined, for
@@ -1999,6 +2005,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
if (arg2 || arg3 || arg4 || arg5)
return -EINVAL;
return current->no_new_privs ? 1 : 0;
+ case PR_MPX_INIT:
+ error = MPX_INIT(me);
+ break;
+ case PR_MPX_RELEASE:
+ error = MPX_RELEASE(me);
+ break;
default:
error = -EINVAL;
break;
--
1.7.1


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