1 #include <linux/errno.h>
2 #include <linux/sched.h>
3 #include <linux/sched/mm.h>
4 #include <linux/syscalls.h>
10 #include <linux/shm.h>
11 #include <linux/stat.h>
12 #include <linux/mman.h>
13 #include <linux/file.h>
14 #include <linux/utsname.h>
15 #include <linux/personality.h>
16 #include <linux/random.h>
17 #include <linux/uaccess.h>
18 #include <linux/elf.h>
21 #include <asm/syscalls.h>
24 * Align a virtual address to avoid aliasing in the I$ on AMD F15h.
26 static unsigned long get_align_mask(void)
28 /* handle 32- and 64-bit case with a single conditional */
29 if (va_align.flags < 0 || !(va_align.flags & (2 - mmap_is_ia32())))
32 if (!(current->flags & PF_RANDOMIZE))
39 * To avoid aliasing in the I$ on AMD F15h, the bits defined by the
40 * va_align.bits, [12:upper_bit), are set to a random value instead of
41 * zeroing them. This random value is computed once per boot. This form
42 * of ASLR is known as "per-boot ASLR".
44 * To achieve this, the random value is added to the info.align_offset
45 * value before calling vm_unmapped_area() or ORed directly to the
48 static unsigned long get_align_bits(void)
50 return va_align.bits & get_align_mask();
53 unsigned long align_vdso_addr(unsigned long addr)
55 unsigned long align_mask = get_align_mask();
56 addr = (addr + align_mask) & ~align_mask;
57 return addr | get_align_bits();
60 static int __init control_va_addr_alignment(char *str)
62 /* guard against enabling this on other CPU families */
63 if (va_align.flags < 0)
72 if (!strcmp(str, "32"))
73 va_align.flags = ALIGN_VA_32;
74 else if (!strcmp(str, "64"))
75 va_align.flags = ALIGN_VA_64;
76 else if (!strcmp(str, "off"))
78 else if (!strcmp(str, "on"))
79 va_align.flags = ALIGN_VA_32 | ALIGN_VA_64;
85 __setup("align_va_addr", control_va_addr_alignment);
87 SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
88 unsigned long, prot, unsigned long, flags,
89 unsigned long, fd, unsigned long, off)
96 error = sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
101 static void find_start_end(unsigned long flags, unsigned long *begin,
104 if (!test_thread_flag(TIF_ADDR32) && (flags & MAP_32BIT)) {
105 /* This is usually used needed to map code in small
106 model, so it needs to be in the first 31bit. Limit
107 it to that. This means we need to move the
108 unmapped base down for this case. This can give
109 conflicts with the heap, but we assume that glibc
110 malloc knows how to fall back to mmap. Give it 1GB
111 of playground for now. -AK */
114 if (current->flags & PF_RANDOMIZE) {
115 *begin = randomize_page(*begin, 0x02000000);
118 *begin = current->mm->mmap_legacy_base;
124 arch_get_unmapped_area(struct file *filp, unsigned long addr,
125 unsigned long len, unsigned long pgoff, unsigned long flags)
127 struct mm_struct *mm = current->mm;
128 struct vm_area_struct *vma;
129 struct vm_unmapped_area_info info;
130 unsigned long begin, end;
132 if (flags & MAP_FIXED)
135 find_start_end(flags, &begin, &end);
141 addr = PAGE_ALIGN(addr);
142 vma = find_vma(mm, addr);
143 if (end - len >= addr &&
144 (!vma || addr + len <= vma->vm_start))
150 info.low_limit = begin;
151 info.high_limit = end;
153 info.align_offset = pgoff << PAGE_SHIFT;
155 info.align_mask = get_align_mask();
156 info.align_offset += get_align_bits();
158 return vm_unmapped_area(&info);
162 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
163 const unsigned long len, const unsigned long pgoff,
164 const unsigned long flags)
166 struct vm_area_struct *vma;
167 struct mm_struct *mm = current->mm;
168 unsigned long addr = addr0;
169 struct vm_unmapped_area_info info;
171 /* requested length too big for entire address space */
175 if (flags & MAP_FIXED)
178 /* for MAP_32BIT mappings we force the legacy mmap base */
179 if (!test_thread_flag(TIF_ADDR32) && (flags & MAP_32BIT))
182 /* requesting a specific address */
184 addr = PAGE_ALIGN(addr);
185 vma = find_vma(mm, addr);
186 if (TASK_SIZE - len >= addr &&
187 (!vma || addr + len <= vma->vm_start))
191 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
193 info.low_limit = PAGE_SIZE;
194 info.high_limit = mm->mmap_base;
196 info.align_offset = pgoff << PAGE_SHIFT;
198 info.align_mask = get_align_mask();
199 info.align_offset += get_align_bits();
201 addr = vm_unmapped_area(&info);
202 if (!(addr & ~PAGE_MASK))
204 VM_BUG_ON(addr != -ENOMEM);
208 * A failed mmap() very likely causes application failure,
209 * so fall back to the bottom-up function here. This scenario
210 * can happen with large stack limits and large mmap()
213 return arch_get_unmapped_area(filp, addr0, len, pgoff, flags);