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Linux/arch/x86/kernel/sys_x86_64.c

  1 #include <linux/errno.h>
  2 #include <linux/sched.h>
  3 #include <linux/syscalls.h>
  4 #include <linux/mm.h>
  5 #include <linux/fs.h>
  6 #include <linux/smp.h>
  7 #include <linux/sem.h>
  8 #include <linux/msg.h>
  9 #include <linux/shm.h>
 10 #include <linux/stat.h>
 11 #include <linux/mman.h>
 12 #include <linux/file.h>
 13 #include <linux/utsname.h>
 14 #include <linux/personality.h>
 15 #include <linux/random.h>
 16 #include <linux/uaccess.h>
 17 #include <linux/elf.h>
 18 
 19 #include <asm/ia32.h>
 20 #include <asm/syscalls.h>
 21 
 22 /*
 23  * Align a virtual address to avoid aliasing in the I$ on AMD F15h.
 24  */
 25 static unsigned long get_align_mask(void)
 26 {
 27         /* handle 32- and 64-bit case with a single conditional */
 28         if (va_align.flags < 0 || !(va_align.flags & (2 - mmap_is_ia32())))
 29                 return 0;
 30 
 31         if (!(current->flags & PF_RANDOMIZE))
 32                 return 0;
 33 
 34         return va_align.mask;
 35 }
 36 
 37 /*
 38  * To avoid aliasing in the I$ on AMD F15h, the bits defined by the
 39  * va_align.bits, [12:upper_bit), are set to a random value instead of
 40  * zeroing them. This random value is computed once per boot. This form
 41  * of ASLR is known as "per-boot ASLR".
 42  *
 43  * To achieve this, the random value is added to the info.align_offset
 44  * value before calling vm_unmapped_area() or ORed directly to the
 45  * address.
 46  */
 47 static unsigned long get_align_bits(void)
 48 {
 49         return va_align.bits & get_align_mask();
 50 }
 51 
 52 unsigned long align_vdso_addr(unsigned long addr)
 53 {
 54         unsigned long align_mask = get_align_mask();
 55         addr = (addr + align_mask) & ~align_mask;
 56         return addr | get_align_bits();
 57 }
 58 
 59 static int __init control_va_addr_alignment(char *str)
 60 {
 61         /* guard against enabling this on other CPU families */
 62         if (va_align.flags < 0)
 63                 return 1;
 64 
 65         if (*str == 0)
 66                 return 1;
 67 
 68         if (*str == '=')
 69                 str++;
 70 
 71         if (!strcmp(str, "32"))
 72                 va_align.flags = ALIGN_VA_32;
 73         else if (!strcmp(str, "64"))
 74                 va_align.flags = ALIGN_VA_64;
 75         else if (!strcmp(str, "off"))
 76                 va_align.flags = 0;
 77         else if (!strcmp(str, "on"))
 78                 va_align.flags = ALIGN_VA_32 | ALIGN_VA_64;
 79         else
 80                 return 0;
 81 
 82         return 1;
 83 }
 84 __setup("align_va_addr", control_va_addr_alignment);
 85 
 86 SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
 87                 unsigned long, prot, unsigned long, flags,
 88                 unsigned long, fd, unsigned long, off)
 89 {
 90         long error;
 91         error = -EINVAL;
 92         if (off & ~PAGE_MASK)
 93                 goto out;
 94 
 95         error = sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
 96 out:
 97         return error;
 98 }
 99 
100 static void find_start_end(unsigned long flags, unsigned long *begin,
101                            unsigned long *end)
102 {
103         if (!test_thread_flag(TIF_ADDR32) && (flags & MAP_32BIT)) {
104                 /* This is usually used needed to map code in small
105                    model, so it needs to be in the first 31bit. Limit
106                    it to that.  This means we need to move the
107                    unmapped base down for this case. This can give
108                    conflicts with the heap, but we assume that glibc
109                    malloc knows how to fall back to mmap. Give it 1GB
110                    of playground for now. -AK */
111                 *begin = 0x40000000;
112                 *end = 0x80000000;
113                 if (current->flags & PF_RANDOMIZE) {
114                         *begin = randomize_page(*begin, 0x02000000);
115                 }
116         } else {
117                 *begin = current->mm->mmap_legacy_base;
118                 *end = TASK_SIZE;
119         }
120 }
121 
122 unsigned long
123 arch_get_unmapped_area(struct file *filp, unsigned long addr,
124                 unsigned long len, unsigned long pgoff, unsigned long flags)
125 {
126         struct mm_struct *mm = current->mm;
127         struct vm_area_struct *vma;
128         struct vm_unmapped_area_info info;
129         unsigned long begin, end;
130 
131         if (flags & MAP_FIXED)
132                 return addr;
133 
134         find_start_end(flags, &begin, &end);
135 
136         if (len > end)
137                 return -ENOMEM;
138 
139         if (addr) {
140                 addr = PAGE_ALIGN(addr);
141                 vma = find_vma(mm, addr);
142                 if (end - len >= addr &&
143                     (!vma || addr + len <= vma->vm_start))
144                         return addr;
145         }
146 
147         info.flags = 0;
148         info.length = len;
149         info.low_limit = begin;
150         info.high_limit = end;
151         info.align_mask = 0;
152         info.align_offset = pgoff << PAGE_SHIFT;
153         if (filp) {
154                 info.align_mask = get_align_mask();
155                 info.align_offset += get_align_bits();
156         }
157         return vm_unmapped_area(&info);
158 }
159 
160 unsigned long
161 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
162                           const unsigned long len, const unsigned long pgoff,
163                           const unsigned long flags)
164 {
165         struct vm_area_struct *vma;
166         struct mm_struct *mm = current->mm;
167         unsigned long addr = addr0;
168         struct vm_unmapped_area_info info;
169 
170         /* requested length too big for entire address space */
171         if (len > TASK_SIZE)
172                 return -ENOMEM;
173 
174         if (flags & MAP_FIXED)
175                 return addr;
176 
177         /* for MAP_32BIT mappings we force the legacy mmap base */
178         if (!test_thread_flag(TIF_ADDR32) && (flags & MAP_32BIT))
179                 goto bottomup;
180 
181         /* requesting a specific address */
182         if (addr) {
183                 addr = PAGE_ALIGN(addr);
184                 vma = find_vma(mm, addr);
185                 if (TASK_SIZE - len >= addr &&
186                                 (!vma || addr + len <= vma->vm_start))
187                         return addr;
188         }
189 
190         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
191         info.length = len;
192         info.low_limit = PAGE_SIZE;
193         info.high_limit = mm->mmap_base;
194         info.align_mask = 0;
195         info.align_offset = pgoff << PAGE_SHIFT;
196         if (filp) {
197                 info.align_mask = get_align_mask();
198                 info.align_offset += get_align_bits();
199         }
200         addr = vm_unmapped_area(&info);
201         if (!(addr & ~PAGE_MASK))
202                 return addr;
203         VM_BUG_ON(addr != -ENOMEM);
204 
205 bottomup:
206         /*
207          * A failed mmap() very likely causes application failure,
208          * so fall back to the bottom-up function here. This scenario
209          * can happen with large stack limits and large mmap()
210          * allocations.
211          */
212         return arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
213 }
214 

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