arch/x86_64/ia32/syscall32.c

   1 /* Copyright 2002,2003 Andi Kleen, SuSE Labs */
   2
   3 /* vsyscall handling for 32bit processes. Map a stub page into it
   4    on demand because 32bit cannot reach the kernel's fixmaps */
   5
   6 #include <linux/mm.h>
   7 #include <linux/string.h>
   8 #include <linux/kernel.h>
   9 #include <linux/gfp.h>
  10 #include <linux/init.h>
  11 #include <linux/stringify.h>
  12 #include <linux/security.h>
  13 #include <asm/proto.h>
  14 #include <asm/tlbflush.h>
  15 #include <asm/ia32_unistd.h>
  16 #include <asm/vsyscall32.h>
  17
  18 extern unsigned char syscall32_syscall[], syscall32_syscall_end[];
  19 extern unsigned char syscall32_sysenter[], syscall32_sysenter_end[];
  20 extern int sysctl_vsyscall32;
  21
  22 static struct page *syscall32_pages[1];
  23 static int use_sysenter = -1;
  24
  25 struct linux_binprm;
  26
  27 /* Setup a VMA at program startup for the vsyscall page */
  28 int syscall32_setup_pages(struct linux_binprm *bprm, int exstack)
  29 {
  30         struct mm_struct *mm = current->mm;
  31         int ret;
  32
  33         down_write(&mm->mmap_sem);
  34         /*
  35          * MAYWRITE to allow gdb to COW and set breakpoints
  36          *
  37          * Make sure the vDSO gets into every core dump.
  38          * Dumping its contents makes post-mortem fully interpretable later
  39          * without matching up the same kernel and hardware config to see
  40          * what PC values meant.
  41          */
  42         /* Could randomize here */
  43         ret = install_special_mapping(mm, VSYSCALL32_BASE, PAGE_SIZE,
  44                                       VM_READ|VM_EXEC|
  45                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
  46                                       VM_ALWAYSDUMP,
  47                                       syscall32_pages);
  48         up_write(&mm->mmap_sem);
  49         return ret;
  50 }
  51
  52 static int __init init_syscall32(void)
  53 {
  54         char *syscall32_page = (void *)get_zeroed_page(GFP_KERNEL);
  55         if (!syscall32_page)
  56                 panic("Cannot allocate syscall32 page");
  57         syscall32_pages[0] = virt_to_page(syscall32_page);
  58         if (use_sysenter > 0) {
  59                 memcpy(syscall32_page, syscall32_sysenter,
  60                        syscall32_sysenter_end - syscall32_sysenter);
  61         } else {
  62                 memcpy(syscall32_page, syscall32_syscall,
  63                        syscall32_syscall_end - syscall32_syscall);
  64         }
  65         return 0;
  66 }
  67
  68 __initcall(init_syscall32);
  69
  70 /* May not be __init: called during resume */
  71 void syscall32_cpu_init(void)
  72 {
  73         if (use_sysenter < 0)
  74                 use_sysenter = (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL);
  75
  76         /* Load these always in case some future AMD CPU supports
  77            SYSENTER from compat mode too. */
  78         checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
  79         checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
  80         checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
  81
  82         wrmsrl(MSR_CSTAR, ia32_cstar_target);
  83 }