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 <asm/proto.h>
  13 #include <asm/tlbflush.h>
  14 #include <asm/ia32_unistd.h>
  15
  16 /* 32bit VDSOs mapped into user space. */
  17 asm(".section \".init.data\",\"aw\"\n"
  18     "syscall32_syscall:\n"
  19     ".incbin \"arch/x86_64/ia32/vsyscall-syscall.so\"\n"
  20     "syscall32_syscall_end:\n"
  21     "syscall32_sysenter:\n"
  22     ".incbin \"arch/x86_64/ia32/vsyscall-sysenter.so\"\n"
  23     "syscall32_sysenter_end:\n"
  24     ".previous");
  25
  26 extern unsigned char syscall32_syscall[], syscall32_syscall_end[];
  27 extern unsigned char syscall32_sysenter[], syscall32_sysenter_end[];
  28 extern int sysctl_vsyscall32;
  29
  30 char *syscall32_page;
  31 static int use_sysenter = -1;
  32
  33 /*
  34  * Map the 32bit vsyscall page on demand.
  35  *
  36  * RED-PEN: This knows too much about high level VM.
  37  *
  38  * Alternative would be to generate a vma with appropriate backing options
  39  * and let it be handled by generic VM.
  40  */
  41 int __map_syscall32(struct mm_struct *mm, unsigned long address)
  42 {
  43         pgd_t *pgd;
  44         pud_t *pud;
  45         pte_t *pte;
  46         pmd_t *pmd;
  47         int err = -ENOMEM;
  48
  49         spin_lock(&mm->page_table_lock);
  50         pgd = pgd_offset(mm, address);
  51         pud = pud_alloc(mm, pgd, address);
  52         if (pud) {
  53                 pmd = pmd_alloc(mm, pud, address);
  54                 if (pmd && (pte = pte_alloc_map(mm, pmd, address)) != NULL) {
  55                         if (pte_none(*pte)) {
  56                                 set_pte(pte,
  57                                         mk_pte(virt_to_page(syscall32_page),
  58                                                PAGE_KERNEL_VSYSCALL32));
  59                         }
  60                         /* Flush only the local CPU. Other CPUs taking a fault
  61                            will just end up here again
  62                            This probably not needed and just paranoia. */
  63                         __flush_tlb_one(address);
  64                         err = 0;
  65                 }
  66         }
  67         spin_unlock(&mm->page_table_lock);
  68         return err;
  69 }
  70
  71 int map_syscall32(struct mm_struct *mm, unsigned long address)
  72 {
  73         int err;
  74         down_read(&mm->mmap_sem);
  75         err = __map_syscall32(mm, address);
  76         up_read(&mm->mmap_sem);
  77         return err;
  78 }
  79
  80 static int __init init_syscall32(void)
  81 {
  82         syscall32_page = (void *)get_zeroed_page(GFP_KERNEL);
  83         if (!syscall32_page)
  84                 panic("Cannot allocate syscall32 page");
  85         SetPageReserved(virt_to_page(syscall32_page));
  86         if (use_sysenter > 0) {
  87                 memcpy(syscall32_page, syscall32_sysenter,
  88                        syscall32_sysenter_end - syscall32_sysenter);
  89         } else {
  90                 memcpy(syscall32_page, syscall32_syscall,
  91                        syscall32_syscall_end - syscall32_syscall);
  92         }
  93         return 0;
  94 }
  95
  96 __initcall(init_syscall32);
  97
  98 /* May not be __init: called during resume */
  99 void syscall32_cpu_init(void)
 100 {
 101         if (use_sysenter < 0)
 102                 use_sysenter = (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL);
 103
 104         /* Load these always in case some future AMD CPU supports
 105            SYSENTER from compat mode too. */
 106         checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
 107         checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
 108         checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
 109
 110         wrmsrl(MSR_CSTAR, ia32_cstar_target);
 111 }