arch/mips/kernel/vdso.c

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 2009, 2010 Cavium Networks, Inc.
   7  */
   8
   9
  10 #include <linux/kernel.h>
  11 #include <linux/err.h>
  12 #include <linux/sched.h>
  13 #include <linux/mm.h>
  14 #include <linux/init.h>
  15 #include <linux/binfmts.h>
  16 #include <linux/elf.h>
  17 #include <linux/vmalloc.h>
  18 #include <linux/unistd.h>
  19 #include <linux/random.h>
  20
  21 #include <asm/vdso.h>
  22 #include <asm/uasm.h>
  23 #include <asm/processor.h>
  24
  25 /*
  26  * Including <asm/unistd.h> would give use the 64-bit syscall numbers ...
  27  */
  28 #define __NR_O32_sigreturn              4119
  29 #define __NR_O32_rt_sigreturn           4193
  30 #define __NR_N32_rt_sigreturn           6211
  31
  32 static struct page *vdso_page;
  33
  34 static void __init install_trampoline(u32 *tramp, unsigned int sigreturn)
  35 {
  36         uasm_i_addiu(&tramp, 2, 0, sigreturn);  /* li v0, sigreturn */
  37         uasm_i_syscall(&tramp, 0);
  38 }
  39
  40 static int __init init_vdso(void)
  41 {
  42         struct mips_vdso *vdso;
  43
  44         vdso_page = alloc_page(GFP_KERNEL);
  45         if (!vdso_page)
  46                 panic("Cannot allocate vdso");
  47
  48         vdso = vmap(&vdso_page, 1, 0, PAGE_KERNEL);
  49         if (!vdso)
  50                 panic("Cannot map vdso");
  51         clear_page(vdso);
  52
  53         install_trampoline(vdso->rt_signal_trampoline, __NR_rt_sigreturn);
  54 #ifdef CONFIG_32BIT
  55         install_trampoline(vdso->signal_trampoline, __NR_sigreturn);
  56 #else
  57         install_trampoline(vdso->n32_rt_signal_trampoline,
  58                            __NR_N32_rt_sigreturn);
  59         install_trampoline(vdso->o32_signal_trampoline, __NR_O32_sigreturn);
  60         install_trampoline(vdso->o32_rt_signal_trampoline,
  61                            __NR_O32_rt_sigreturn);
  62 #endif
  63
  64         vunmap(vdso);
  65
  66         return 0;
  67 }
  68 subsys_initcall(init_vdso);
  69
  70 static unsigned long vdso_addr(unsigned long start)
  71 {
  72         unsigned long offset = 0UL;
  73
  74         if (current->flags & PF_RANDOMIZE) {
  75                 offset = get_random_int();
  76                 offset <<= PAGE_SHIFT;
  77                 if (TASK_IS_32BIT_ADDR)
  78                         offset &= 0xfffffful;
  79                 else
  80                         offset &= 0xffffffful;
  81         }
  82
  83         return STACK_TOP + offset;
  84 }
  85
  86 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  87 {
  88         int ret;
  89         unsigned long addr;
  90         struct mm_struct *mm = current->mm;
  91
  92         down_write(&mm->mmap_sem);
  93
  94         addr = vdso_addr(mm->start_stack);
  95
  96         addr = get_unmapped_area(NULL, addr, PAGE_SIZE, 0, 0);
  97         if (IS_ERR_VALUE(addr)) {
  98                 ret = addr;
  99                 goto up_fail;
 100         }
 101
 102         ret = install_special_mapping(mm, addr, PAGE_SIZE,
 103                                       VM_READ|VM_EXEC|
 104                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 105                                       &vdso_page);
 106
 107         if (ret)
 108                 goto up_fail;
 109
 110         mm->context.vdso = (void *)addr;
 111
 112 up_fail:
 113         up_write(&mm->mmap_sem);
 114         return ret;
 115 }
 116
 117 const char *arch_vma_name(struct vm_area_struct *vma)
 118 {
 119         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
 120                 return "[vdso]";
 121         return NULL;
 122 }