[PATCH v6 02/10] x86, mpx: add MPX specific mmap interface

[Qiaowei Ren]

This patch adds one MPX specific mmap interface, which only handles
mpx related maps, including bounds table and bounds directory.

In order to track MPX specific memory usage, this interface is added
to stick new vm_flag VM_MPX in the vma_area_struct when create a
bounds table or bounds directory.

Signed-off-by: Qiaowei Ren <qiaowei.ren@xxxxxxxxx>
---
 arch/x86/Kconfig           |    4 +++
 arch/x86/include/asm/mpx.h |   38 ++++++++++++++++++++++++++++
 arch/x86/mm/Makefile       |    2 +
 arch/x86/mm/mpx.c          |   58 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 102 insertions(+), 0 deletions(-)
 create mode 100644 arch/x86/include/asm/mpx.h
 create mode 100644 arch/x86/mm/mpx.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 25d2c6f..0194790 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -237,6 +237,10 @@ config HAVE_INTEL_TXT
 	def_bool y
 	depends on INTEL_IOMMU && ACPI
 
+config X86_INTEL_MPX
+	def_bool y
+	depends on CPU_SUP_INTEL
+
 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
new file mode 100644
index 0000000..5725ac4
--- /dev/null
+++ b/arch/x86/include/asm/mpx.h
@@ -0,0 +1,38 @@
+#ifndef _ASM_X86_MPX_H
+#define _ASM_X86_MPX_H
+
+#include <linux/types.h>
+#include <asm/ptrace.h>
+
+#ifdef CONFIG_X86_64
+
+/* upper 28 bits [47:20] of the virtual address in 64-bit used to
+ * index into bounds directory (BD).
+ */
+#define MPX_BD_ENTRY_OFFSET	28
+#define MPX_BD_ENTRY_SHIFT	3
+/* bits [19:3] of the virtual address in 64-bit used to index into
+ * bounds table (BT).
+ */
+#define MPX_BT_ENTRY_OFFSET	17
+#define MPX_BT_ENTRY_SHIFT	5
+#define MPX_IGN_BITS		3
+
+#else
+
+#define MPX_BD_ENTRY_OFFSET	20
+#define MPX_BD_ENTRY_SHIFT	2
+#define MPX_BT_ENTRY_OFFSET	10
+#define MPX_BT_ENTRY_SHIFT	4
+#define MPX_IGN_BITS		2
+
+#endif
+
+#define MPX_BD_SIZE_BYTES (1UL<<(MPX_BD_ENTRY_OFFSET+MPX_BD_ENTRY_SHIFT))
+#define MPX_BT_SIZE_BYTES (1UL<<(MPX_BT_ENTRY_OFFSET+MPX_BT_ENTRY_SHIFT))
+
+#define MPX_BNDSTA_ERROR_CODE	0x3
+
+unsigned long mpx_mmap(unsigned long len);
+
+#endif /* _ASM_X86_MPX_H */
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 6a19ad9..ecfdc46 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -30,3 +30,5 @@ obj-$(CONFIG_ACPI_NUMA)		+= srat.o
 obj-$(CONFIG_NUMA_EMU)		+= numa_emulation.o
 
 obj-$(CONFIG_MEMTEST)		+= memtest.o
+
+obj-$(CONFIG_X86_INTEL_MPX)	+= mpx.o
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
new file mode 100644
index 0000000..546c5d1
--- /dev/null
+++ b/arch/x86/mm/mpx.c
@@ -0,0 +1,58 @@
+#include <linux/kernel.h>
+#include <linux/syscalls.h>
+#include <asm/mpx.h>
+#include <asm/mman.h>
+#include <linux/sched/sysctl.h>
+
+/*
+ * this is really a simplified "vm_mmap". it only handles mpx
+ * related maps, including bounds table and bounds directory.
+ *
+ * here we can stick new vm_flag VM_MPX in the vma_area_struct
+ * when create a bounds table or bounds directory, in order to
+ * track MPX specific memory.
+ */
+unsigned long mpx_mmap(unsigned long len)
+{
+	unsigned long ret;
+	unsigned long addr, pgoff;
+	struct mm_struct *mm = current->mm;
+	vm_flags_t vm_flags;
+
+	/* Only bounds table and bounds directory can be allocated here */
+	if (len != MPX_BD_SIZE_BYTES && len != MPX_BT_SIZE_BYTES)
+		return -EINVAL;
+
+	down_write(&mm->mmap_sem);
+
+	/* Too many mappings? */
+	if (mm->map_count > sysctl_max_map_count) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/* Obtain the address to map to. we verify (or select) it and ensure
+	 * that it represents a valid section of the address space.
+	 */
+	addr = get_unmapped_area(NULL, 0, len, 0, MAP_ANONYMOUS | MAP_PRIVATE);
+	if (addr & ~PAGE_MASK) {
+		ret = addr;
+		goto out;
+	}
+
+	vm_flags = VM_READ | VM_WRITE | VM_MPX |
+			mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
+
+	/* Make bounds tables and bouds directory unlocked. */
+	if (vm_flags & VM_LOCKED)
+		vm_flags &= ~VM_LOCKED;
+
+	/* Set pgoff according to addr for anon_vma */
+	pgoff = addr >> PAGE_SHIFT;
+
+	ret = mmap_region(NULL, addr, len, vm_flags, pgoff);
+
+out:
+	up_write(&mm->mmap_sem);
+	return ret;
+}
-- 
1.7.1

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