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
  20 #include <asm/vdso.h>
  21 #include <asm/uasm.h>
  22
  23 /*
  24  * Including <asm/unistd.h> would give use the 64-bit syscall numbers ...
  25  */
  26 #define __NR_O32_sigreturn              4119
  27 #define __NR_O32_rt_sigreturn           4193
  28 #define __NR_N32_rt_sigreturn           6211
  29
  30 static struct page *vdso_page;
  31
  32 static void __init install_trampoline(u32 *tramp, unsigned int sigreturn)
  33 {
  34         uasm_i_addiu(&tramp, 2, 0, sigreturn);  /* li v0, sigreturn */
  35         uasm_i_syscall(&tramp, 0);
  36 }
  37
  38 static int __init init_vdso(void)
  39 {
  40         struct mips_vdso *vdso;
  41
  42         vdso_page = alloc_page(GFP_KERNEL);
  43         if (!vdso_page)
  44                 panic("Cannot allocate vdso");
  45
  46         vdso = vmap(&vdso_page, 1, 0, PAGE_KERNEL);
  47         if (!vdso)
  48                 panic("Cannot map vdso");
  49         clear_page(vdso);
  50
  51         install_trampoline(vdso->rt_signal_trampoline, __NR_rt_sigreturn);
  52 #ifdef CONFIG_32BIT
  53         install_trampoline(vdso->signal_trampoline, __NR_sigreturn);
  54 #else
  55         install_trampoline(vdso->n32_rt_signal_trampoline,
  56                            __NR_N32_rt_sigreturn);
  57         install_trampoline(vdso->o32_signal_trampoline, __NR_O32_sigreturn);
  58         install_trampoline(vdso->o32_rt_signal_trampoline,
  59                            __NR_O32_rt_sigreturn);
  60 #endif
  61
  62         vunmap(vdso);
  63
  64         return 0;
  65 }
  66 subsys_initcall(init_vdso);
  67
  68 static unsigned long vdso_addr(unsigned long start)
  69 {
  70         return STACK_TOP;
  71 }
  72
  73 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  74 {
  75         int ret;
  76         unsigned long addr;
  77         struct mm_struct *mm = current->mm;
  78
  79         down_write(&mm->mmap_sem);
  80
  81         addr = vdso_addr(mm->start_stack);
  82
  83         addr = get_unmapped_area(NULL, addr, PAGE_SIZE, 0, 0);
  84         if (IS_ERR_VALUE(addr)) {
  85                 ret = addr;
  86                 goto up_fail;
  87         }
  88
  89         ret = install_special_mapping(mm, addr, PAGE_SIZE,
  90                                       VM_READ|VM_EXEC|
  91                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
  92                                       VM_ALWAYSDUMP,
  93                                       &vdso_page);
  94
  95         if (ret)
  96                 goto up_fail;
  97
  98         mm->context.vdso = (void *)addr;
  99
 100 up_fail:
 101         up_write(&mm->mmap_sem);
 102         return ret;
 103 }
 104
 105 const char *arch_vma_name(struct vm_area_struct *vma)
 106 {
 107         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
 108                 return "[vdso]";
 109         return NULL;
 110 }