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 #include <linux/hugetlb.h>
  22
  23 #include <asm/elf.h>
  24 #include <asm/ia32.h>
  25
  26 /*
  27  * Align a virtual address to avoid aliasing in the I$ on AMD F15h.
  28  */
  29 static unsigned long get_align_mask(struct file *filp)
  30 {
  31         if (filp && is_file_hugepages(filp))
  32                 return huge_page_mask_align(filp);
  33         /* handle 32- and 64-bit case with a single conditional */
  34         if (va_align.flags < 0 || !(va_align.flags & (2 - mmap_is_ia32())))
  35                 return 0;
  36
  37         if (!(current->flags & PF_RANDOMIZE))
  38                 return 0;
  39
  40         return va_align.mask;
  41 }
  42
  43 /*
  44  * To avoid aliasing in the I$ on AMD F15h, the bits defined by the
  45  * va_align.bits, [12:upper_bit), are set to a random value instead of
  46  * zeroing them. This random value is computed once per boot. This form
  47  * of ASLR is known as "per-boot ASLR".
  48  *
  49  * To achieve this, the random value is added to the info.align_offset
  50  * value before calling vm_unmapped_area() or ORed directly to the
  51  * address.
  52  */
  53 static unsigned long get_align_bits(void)
  54 {
  55         return va_align.bits & get_align_mask(NULL);
  56 }
  57
  58 static int __init control_va_addr_alignment(char *str)
  59 {
  60         /* guard against enabling this on other CPU families */
  61         if (va_align.flags < 0)
  62                 return 1;
  63
  64         if (*str == 0)
  65                 return 1;
  66
  67         if (!strcmp(str, "32"))
  68                 va_align.flags = ALIGN_VA_32;
  69         else if (!strcmp(str, "64"))
  70                 va_align.flags = ALIGN_VA_64;
  71         else if (!strcmp(str, "off"))
  72                 va_align.flags = 0;
  73         else if (!strcmp(str, "on"))
  74                 va_align.flags = ALIGN_VA_32 | ALIGN_VA_64;
  75         else
  76                 pr_warn("invalid option value: 'align_va_addr=%s'\n", str);
  77
  78         return 1;
  79 }
  80 __setup("align_va_addr=", control_va_addr_alignment);
  81
  82 SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
  83                 unsigned long, prot, unsigned long, flags,
  84                 unsigned long, fd, unsigned long, off)
  85 {
  86         if (off & ~PAGE_MASK)
  87                 return -EINVAL;
  88
  89         return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
  90 }
  91
  92 static void find_start_end(unsigned long addr, unsigned long flags,
  93                 unsigned long *begin, unsigned long *end)
  94 {
  95         if (!in_32bit_syscall() && (flags & MAP_32BIT)) {
  96                 /* This is usually used needed to map code in small
  97                    model, so it needs to be in the first 31bit. Limit
  98                    it to that.  This means we need to move the
  99                    unmapped base down for this case. This can give
 100                    conflicts with the heap, but we assume that glibc
 101                    malloc knows how to fall back to mmap. Give it 1GB
 102                    of playground for now. -AK */
 103                 *begin = 0x40000000;
 104                 *end = 0x80000000;
 105                 if (current->flags & PF_RANDOMIZE) {
 106                         *begin = randomize_page(*begin, 0x02000000);
 107                 }
 108                 return;
 109         }
 110
 111         *begin  = get_mmap_base(1);
 112         if (in_32bit_syscall())
 113                 *end = task_size_32bit();
 114         else
 115                 *end = task_size_64bit(addr > DEFAULT_MAP_WINDOW);
 116 }
 117
 118 static inline unsigned long stack_guard_placement(vm_flags_t vm_flags)
 119 {
 120         if (vm_flags & VM_SHADOW_STACK)
 121                 return PAGE_SIZE;
 122
 123         return 0;
 124 }
 125
 126 unsigned long
 127 arch_get_unmapped_area(struct file *filp, unsigned long addr, unsigned long len,
 128                        unsigned long pgoff, unsigned long flags, vm_flags_t vm_flags)
 129 {
 130         struct mm_struct *mm = current->mm;
 131         struct vm_area_struct *vma;
 132         struct vm_unmapped_area_info info = {};
 133         unsigned long begin, end;
 134
 135         if (flags & MAP_FIXED)
 136                 return addr;
 137
 138         find_start_end(addr, flags, &begin, &end);
 139
 140         if (len > end)
 141                 return -ENOMEM;
 142
 143         if (addr) {
 144                 addr = PAGE_ALIGN(addr);
 145                 vma = find_vma(mm, addr);
 146                 if (end - len >= addr &&
 147                     (!vma || addr + len <= vm_start_gap(vma)))
 148                         return addr;
 149         }
 150
 151         info.length = len;
 152         info.low_limit = begin;
 153         info.high_limit = end;
 154         if (!(filp && is_file_hugepages(filp))) {
 155                 info.align_offset = pgoff << PAGE_SHIFT;
 156                 info.start_gap = stack_guard_placement(vm_flags);
 157         }
 158         if (filp) {
 159                 info.align_mask = get_align_mask(filp);
 160                 info.align_offset += get_align_bits();
 161         }
 162
 163         return vm_unmapped_area(&info);
 164 }
 165
 166 unsigned long
 167 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr0,
 168                           unsigned long len, unsigned long pgoff,
 169                           unsigned long flags, vm_flags_t vm_flags)
 170 {
 171         struct vm_area_struct *vma;
 172         struct mm_struct *mm = current->mm;
 173         unsigned long addr = addr0;
 174         struct vm_unmapped_area_info info = {};
 175
 176         /* requested length too big for entire address space */
 177         if (len > TASK_SIZE)
 178                 return -ENOMEM;
 179
 180         /* No address checking. See comment at mmap_address_hint_valid() */
 181         if (flags & MAP_FIXED)
 182                 return addr;
 183
 184         /* for MAP_32BIT mappings we force the legacy mmap base */
 185         if (!in_32bit_syscall() && (flags & MAP_32BIT))
 186                 goto bottomup;
 187
 188         /* requesting a specific address */
 189         if (addr) {
 190                 addr &= PAGE_MASK;
 191                 if (!mmap_address_hint_valid(addr, len))
 192                         goto get_unmapped_area;
 193
 194                 vma = find_vma(mm, addr);
 195                 if (!vma || addr + len <= vm_start_gap(vma))
 196                         return addr;
 197         }
 198 get_unmapped_area:
 199
 200         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 201         info.length = len;
 202         if (!in_32bit_syscall() && (flags & MAP_ABOVE4G))
 203                 info.low_limit = SZ_4G;
 204         else
 205                 info.low_limit = PAGE_SIZE;
 206
 207         info.high_limit = get_mmap_base(0);
 208         if (!(filp && is_file_hugepages(filp))) {
 209                 info.start_gap = stack_guard_placement(vm_flags);
 210                 info.align_offset = pgoff << PAGE_SHIFT;
 211         }
 212
 213         /*
 214          * If hint address is above DEFAULT_MAP_WINDOW, look for unmapped area
 215          * in the full address space.
 216          *
 217          * !in_32bit_syscall() check to avoid high addresses for x32
 218          * (and make it no op on native i386).
 219          */
 220         if (addr > DEFAULT_MAP_WINDOW && !in_32bit_syscall())
 221                 info.high_limit += TASK_SIZE_MAX - DEFAULT_MAP_WINDOW;
 222
 223         if (filp) {
 224                 info.align_mask = get_align_mask(filp);
 225                 info.align_offset += get_align_bits();
 226         }
 227         addr = vm_unmapped_area(&info);
 228         if (!(addr & ~PAGE_MASK))
 229                 return addr;
 230         VM_BUG_ON(addr != -ENOMEM);
 231
 232 bottomup:
 233         /*
 234          * A failed mmap() very likely causes application failure,
 235          * so fall back to the bottom-up function here. This scenario
 236          * can happen with large stack limits and large mmap()
 237          * allocations.
 238          */
 239         return arch_get_unmapped_area(filp, addr0, len, pgoff, flags, 0);
 240 }