Qiaowei Ren | 57319d8 | 2014-11-14 07:18:27 -0800 | [diff] [blame^] | 1 | /* |
| 2 | * mpx.c - Memory Protection eXtensions |
| 3 | * |
| 4 | * Copyright (c) 2014, Intel Corporation. |
| 5 | * Qiaowei Ren <qiaowei.ren@intel.com> |
| 6 | * Dave Hansen <dave.hansen@intel.com> |
| 7 | */ |
| 8 | #include <linux/kernel.h> |
| 9 | #include <linux/syscalls.h> |
| 10 | #include <linux/sched/sysctl.h> |
| 11 | |
| 12 | #include <asm/mman.h> |
| 13 | #include <asm/mpx.h> |
| 14 | |
| 15 | static const char *mpx_mapping_name(struct vm_area_struct *vma) |
| 16 | { |
| 17 | return "[mpx]"; |
| 18 | } |
| 19 | |
| 20 | static struct vm_operations_struct mpx_vma_ops = { |
| 21 | .name = mpx_mapping_name, |
| 22 | }; |
| 23 | |
| 24 | /* |
| 25 | * This is really a simplified "vm_mmap". it only handles MPX |
| 26 | * bounds tables (the bounds directory is user-allocated). |
| 27 | * |
| 28 | * Later on, we use the vma->vm_ops to uniquely identify these |
| 29 | * VMAs. |
| 30 | */ |
| 31 | static unsigned long mpx_mmap(unsigned long len) |
| 32 | { |
| 33 | unsigned long ret; |
| 34 | unsigned long addr, pgoff; |
| 35 | struct mm_struct *mm = current->mm; |
| 36 | vm_flags_t vm_flags; |
| 37 | struct vm_area_struct *vma; |
| 38 | |
| 39 | /* Only bounds table and bounds directory can be allocated here */ |
| 40 | if (len != MPX_BD_SIZE_BYTES && len != MPX_BT_SIZE_BYTES) |
| 41 | return -EINVAL; |
| 42 | |
| 43 | down_write(&mm->mmap_sem); |
| 44 | |
| 45 | /* Too many mappings? */ |
| 46 | if (mm->map_count > sysctl_max_map_count) { |
| 47 | ret = -ENOMEM; |
| 48 | goto out; |
| 49 | } |
| 50 | |
| 51 | /* Obtain the address to map to. we verify (or select) it and ensure |
| 52 | * that it represents a valid section of the address space. |
| 53 | */ |
| 54 | addr = get_unmapped_area(NULL, 0, len, 0, MAP_ANONYMOUS | MAP_PRIVATE); |
| 55 | if (addr & ~PAGE_MASK) { |
| 56 | ret = addr; |
| 57 | goto out; |
| 58 | } |
| 59 | |
| 60 | vm_flags = VM_READ | VM_WRITE | VM_MPX | |
| 61 | mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC; |
| 62 | |
| 63 | /* Set pgoff according to addr for anon_vma */ |
| 64 | pgoff = addr >> PAGE_SHIFT; |
| 65 | |
| 66 | ret = mmap_region(NULL, addr, len, vm_flags, pgoff); |
| 67 | if (IS_ERR_VALUE(ret)) |
| 68 | goto out; |
| 69 | |
| 70 | vma = find_vma(mm, ret); |
| 71 | if (!vma) { |
| 72 | ret = -ENOMEM; |
| 73 | goto out; |
| 74 | } |
| 75 | vma->vm_ops = &mpx_vma_ops; |
| 76 | |
| 77 | if (vm_flags & VM_LOCKED) { |
| 78 | up_write(&mm->mmap_sem); |
| 79 | mm_populate(ret, len); |
| 80 | return ret; |
| 81 | } |
| 82 | |
| 83 | out: |
| 84 | up_write(&mm->mmap_sem); |
| 85 | return ret; |
| 86 | } |