arch/x86/kernel/sys_x86_64.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/compat.h>
   3 #include <linux/errno.h>
   4 #include <linux/sched.h>
   5 #include <linux/sched/mm.h>
   6 #include <linux/syscalls.h>
   7 #include <linux/mm.h>
   8 #include <linux/fs.h>
   9 #include <linux/smp.h>
  10 #include <linux/sem.h>
  11 #include <linux/msg.h>
  12 #include <linux/shm.h>
  13 #include <linux/stat.h>
  14 #include <linux/mman.h>
  15 #include <linux/file.h>
  16 #include <linux/utsname.h>
  17 #include <linux/personality.h>
  18 #include <linux/random.h>
  19 #include <linux/uaccess.h>
  20 #include <linux/elf.h>
  21
  22 #include <asm/elf.h>
  23 #include <asm/ia32.h>
  24
  25 /*
  26  * Align a virtual address to avoid aliasing in the I$ on AMD F15h.
  27  */
  28 static unsigned long get_align_mask(void)
  29 {
  30         /* handle 32- and 64-bit case with a single conditional */
  31         if (va_align.flags < 0 || !(va_align.flags & (2 - mmap_is_ia32())))
  32                 return 0;
  33
  34         if (!(current->flags & PF_RANDOMIZE))
  35                 return 0;
  36
  37         return va_align.mask;
  38 }
  39
  40 /*
  41  * To avoid aliasing in the I$ on AMD F15h, the bits defined by the
  42  * va_align.bits, [12:upper_bit), are set to a random value instead of
  43  * zeroing them. This random value is computed once per boot. This form
  44  * of ASLR is known as "per-boot ASLR".
  45  *
  46  * To achieve this, the random value is added to the info.align_offset
  47  * value before calling vm_unmapped_area() or ORed directly to the
  48  * address.
  49  */
  50 static unsigned long get_align_bits(void)
  51 {
  52         return va_align.bits & get_align_mask();
  53 }
  54
  55 unsigned long align_vdso_addr(unsigned long addr)
  56 {
  57         unsigned long align_mask = get_align_mask();
  58         addr = (addr + align_mask) & ~align_mask;
  59         return addr | get_align_bits();
  60 }
  61
  62 static int __init control_va_addr_alignment(char *str)
  63 {
  64         /* guard against enabling this on other CPU families */
  65         if (va_align.flags < 0)
  66                 return 1;
  67
  68         if (*str == 0)
  69                 return 1;
  70
  71         if (*str == '=')
  72                 str++;
  73
  74         if (!strcmp(str, "32"))
  75                 va_align.flags = ALIGN_VA_32;
  76         else if (!strcmp(str, "64"))
  77                 va_align.flags = ALIGN_VA_64;
  78         else if (!strcmp(str, "off"))
  79                 va_align.flags = 0;
  80         else if (!strcmp(str, "on"))
  81                 va_align.flags = ALIGN_VA_32 | ALIGN_VA_64;
  82         else
  83                 return 0;
  84
  85         return 1;
  86 }
  87 __setup("align_va_addr", control_va_addr_alignment);
  88
  89 SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
  90                 unsigned long, prot, unsigned long, flags,
  91                 unsigned long, fd, unsigned long, off)
  92 {
  93         if (off & ~PAGE_MASK)
  94                 return -EINVAL;
  95
  96         return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
  97 }
  98
  99 static void find_start_end(unsigned long addr, unsigned long flags,
 100                 unsigned long *begin, unsigned long *end)
 101 {
 102         if (!in_32bit_syscall() && (flags & MAP_32BIT)) {
 103                 /* This is usually used needed to map code in small
 104                    model, so it needs to be in the first 31bit. Limit
 105                    it to that.  This means we need to move the
 106                    unmapped base down for this case. This can give
 107                    conflicts with the heap, but we assume that glibc
 108                    malloc knows how to fall back to mmap. Give it 1GB
 109                    of playground for now. -AK */
 110                 *begin = 0x40000000;
 111                 *end = 0x80000000;
 112                 if (current->flags & PF_RANDOMIZE) {
 113                         *begin = randomize_page(*begin, 0x02000000);
 114                 }
 115                 return;
 116         }
 117
 118         *begin  = get_mmap_base(1);
 119         if (in_32bit_syscall())
 120                 *end = task_size_32bit();
 121         else
 122                 *end = task_size_64bit(addr > DEFAULT_MAP_WINDOW);
 123 }
 124
 125 unsigned long
 126 arch_get_unmapped_area(struct file *filp, unsigned long addr,
 127                 unsigned long len, unsigned long pgoff, unsigned long flags)
 128 {
 129         struct mm_struct *mm = current->mm;
 130         struct vm_area_struct *vma;
 131         struct vm_unmapped_area_info info;
 132         unsigned long begin, end;
 133
 134         if (flags & MAP_FIXED)
 135                 return addr;
 136
 137         find_start_end(addr, flags, &begin, &end);
 138
 139         if (len > end)
 140                 return -ENOMEM;
 141
 142         if (addr) {
 143                 addr = PAGE_ALIGN(addr);
 144                 vma = find_vma(mm, addr);
 145                 if (end - len >= addr &&
 146                     (!vma || addr + len <= vm_start_gap(vma)))
 147                         return addr;
 148         }
 149
 150         info.flags = 0;
 151         info.length = len;
 152         info.low_limit = begin;
 153         info.high_limit = end;
 154         info.align_mask = 0;
 155         info.align_offset = pgoff << PAGE_SHIFT;
 156         if (filp) {
 157                 info.align_mask = get_align_mask();
 158                 info.align_offset += get_align_bits();
 159         }
 160         return vm_unmapped_area(&info);
 161 }
 162
 163 unsigned long
 164 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 165                           const unsigned long len, const unsigned long pgoff,
 166                           const unsigned long flags)
 167 {
 168         struct vm_area_struct *vma;
 169         struct mm_struct *mm = current->mm;
 170         unsigned long addr = addr0;
 171         struct vm_unmapped_area_info info;
 172
 173         /* requested length too big for entire address space */
 174         if (len > TASK_SIZE)
 175                 return -ENOMEM;
 176
 177         /* No address checking. See comment at mmap_address_hint_valid() */
 178         if (flags & MAP_FIXED)
 179                 return addr;
 180
 181         /* for MAP_32BIT mappings we force the legacy mmap base */
 182         if (!in_32bit_syscall() && (flags & MAP_32BIT))
 183                 goto bottomup;
 184
 185         /* requesting a specific address */
 186         if (addr) {
 187                 addr &= PAGE_MASK;
 188                 if (!mmap_address_hint_valid(addr, len))
 189                         goto get_unmapped_area;
 190
 191                 vma = find_vma(mm, addr);
 192                 if (!vma || addr + len <= vm_start_gap(vma))
 193                         return addr;
 194         }
 195 get_unmapped_area:
 196
 197         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 198         info.length = len;
 199         info.low_limit = PAGE_SIZE;
 200         info.high_limit = get_mmap_base(0);
 201
 202         /*
 203          * If hint address is above DEFAULT_MAP_WINDOW, look for unmapped area
 204          * in the full address space.
 205          *
 206          * !in_32bit_syscall() check to avoid high addresses for x32
 207          * (and make it no op on native i386).
 208          */
 209         if (addr > DEFAULT_MAP_WINDOW && !in_32bit_syscall())
 210                 info.high_limit += TASK_SIZE_MAX - DEFAULT_MAP_WINDOW;
 211
 212         info.align_mask = 0;
 213         info.align_offset = pgoff << PAGE_SHIFT;
 214         if (filp) {
 215                 info.align_mask = get_align_mask();
 216                 info.align_offset += get_align_bits();
 217         }
 218         addr = vm_unmapped_area(&info);
 219         if (!(addr & ~PAGE_MASK))
 220                 return addr;
 221         VM_BUG_ON(addr != -ENOMEM);
 222
 223 bottomup:
 224         /*
 225          * A failed mmap() very likely causes application failure,
 226          * so fall back to the bottom-up function here. This scenario
 227          * can happen with large stack limits and large mmap()
 228          * allocations.
 229          */
 230         return arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
 231 }