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 __initdata = -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         pte_t *pte;
  44         pmd_t *pmd;
  45         int err = 0;
  46
  47         spin_lock(&mm->page_table_lock);
  48         pmd = pmd_alloc(mm, pgd_offset(mm, address), address);
  49         if (pmd && (pte = pte_alloc_map(mm, pmd, address)) != NULL) {
  50                 if (pte_none(*pte)) {
  51                         set_pte(pte,
  52                                 mk_pte(virt_to_page(syscall32_page),
  53                                        PAGE_KERNEL_VSYSCALL));
  54                 }
  55                 /* Flush only the local CPU. Other CPUs taking a fault
  56                    will just end up here again */
  57                 __flush_tlb_one(address);
  58         } else
  59                 err = -ENOMEM;
  60         spin_unlock(&mm->page_table_lock);
  61         return err;
  62 }
  63
  64 int map_syscall32(struct mm_struct *mm, unsigned long address)
  65 {
  66         int err;
  67         down_read(&mm->mmap_sem);
  68         err = __map_syscall32(mm, address);
  69         up_read(&mm->mmap_sem);
  70         return err;
  71 }
  72
  73 static int __init init_syscall32(void)
  74 {
  75         syscall32_page = (void *)get_zeroed_page(GFP_KERNEL);
  76         if (!syscall32_page)
  77                 panic("Cannot allocate syscall32 page");
  78         SetPageReserved(virt_to_page(syscall32_page));
  79         if (use_sysenter > 0) {
  80                 memcpy(syscall32_page, syscall32_sysenter,
  81                        syscall32_sysenter_end - syscall32_sysenter);
  82         } else {
  83                 memcpy(syscall32_page, syscall32_syscall,
  84                        syscall32_syscall_end - syscall32_syscall);
  85         }
  86         return 0;
  87 }
  88
  89 __initcall(init_syscall32);
  90
  91 /* May not be __init: called during resume */
  92 void syscall32_cpu_init(void)
  93 {
  94         if (use_sysenter < 0)
  95                 use_sysenter = (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL);
  96
  97         /* Load these always in case some future AMD CPU supports
  98            SYSENTER from compat mode too. */
  99         checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
 100         checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
 101         checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
 102
 103         wrmsrl(MSR_CSTAR, ia32_cstar_target);
 104 }