LXR linux/arch/um/kernel/skas/mmu.c

   1/*
   2 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
   3 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   4 * Licensed under the GPL
   5 */
   6
   7#include <linux/mm.h>
   8#include <linux/sched.h>
   9#include <linux/slab.h>
  10#include <asm/pgalloc.h>
  11#include <asm/pgtable.h>
  12#include <asm/sections.h>
  13#include <as-layout.h>
  14#include <os.h>
  15#include <skas.h>
  16
  17static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
  18                         unsigned long kernel)
  19{
  20        pgd_t *pgd;
  21        pud_t *pud;
  22        pmd_t *pmd;
  23        pte_t *pte;
  24
  25        pgd = pgd_offset(mm, proc);
  26        pud = pud_alloc(mm, pgd, proc);
  27        if (!pud)
  28                goto out;
  29
  30        pmd = pmd_alloc(mm, pud, proc);
  31        if (!pmd)
  32                goto out_pmd;
  33
  34        pte = pte_alloc_map(mm, pmd, proc);
  35        if (!pte)
  36                goto out_pte;
  37
  38        *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
  39        *pte = pte_mkread(*pte);
  40        return 0;
  41
  42 out_pte:
  43        pmd_free(mm, pmd);
  44 out_pmd:
  45        pud_free(mm, pud);
  46 out:
  47        return -ENOMEM;
  48}
  49
  50int init_new_context(struct task_struct *task, struct mm_struct *mm)
  51{
  52        struct mm_context *from_mm = NULL;
  53        struct mm_context *to_mm = &mm->context;
  54        unsigned long stack = 0;
  55        int ret = -ENOMEM;
  56
  57        stack = get_zeroed_page(GFP_KERNEL);
  58        if (stack == 0)
  59                goto out;
  60
  61        to_mm->id.stack = stack;
  62        if (current->mm != NULL && current->mm != &init_mm)
  63                from_mm = &current->mm->context;
  64
  65        block_signals();
  66        if (from_mm)
  67                to_mm->id.u.pid = copy_context_skas0(stack,
  68                                                     from_mm->id.u.pid);
  69        else to_mm->id.u.pid = start_userspace(stack);
  70        unblock_signals();
  71
  72        if (to_mm->id.u.pid < 0) {
  73                ret = to_mm->id.u.pid;
  74                goto out_free;
  75        }
  76
  77        ret = init_new_ldt(to_mm, from_mm);
  78        if (ret < 0) {
  79                printk(KERN_ERR "init_new_context_skas - init_ldt"
  80                       " failed, errno = %d\n", ret);
  81                goto out_free;
  82        }
  83
  84        return 0;
  85
  86 out_free:
  87        if (to_mm->id.stack != 0)
  88                free_page(to_mm->id.stack);
  89 out:
  90        return ret;
  91}
  92
  93void uml_setup_stubs(struct mm_struct *mm)
  94{
  95        int err, ret;
  96
  97        ret = init_stub_pte(mm, STUB_CODE,
  98                            (unsigned long) __syscall_stub_start);
  99        if (ret)
 100                goto out;
 101
 102        ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
 103        if (ret)
 104                goto out;
 105
 106        mm->context.stub_pages[0] = virt_to_page(__syscall_stub_start);
 107        mm->context.stub_pages[1] = virt_to_page(mm->context.id.stack);
 108
 109        /* dup_mmap already holds mmap_sem */
 110        err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
 111                                      VM_READ | VM_MAYREAD | VM_EXEC |
 112                                      VM_MAYEXEC | VM_DONTCOPY | VM_PFNMAP,
 113                                      mm->context.stub_pages);
 114        if (err) {
 115                printk(KERN_ERR "install_special_mapping returned %d\n", err);
 116                goto out;
 117        }
 118        return;
 119
 120out:
 121        force_sigsegv(SIGSEGV, current);
 122}
 123
 124void arch_exit_mmap(struct mm_struct *mm)
 125{
 126        pte_t *pte;
 127
 128        pte = virt_to_pte(mm, STUB_CODE);
 129        if (pte != NULL)
 130                pte_clear(mm, STUB_CODE, pte);
 131
 132        pte = virt_to_pte(mm, STUB_DATA);
 133        if (pte == NULL)
 134                return;
 135
 136        pte_clear(mm, STUB_DATA, pte);
 137}
 138
 139void destroy_context(struct mm_struct *mm)
 140{
 141        struct mm_context *mmu = &mm->context;
 142
 143        /*
 144         * If init_new_context wasn't called, this will be
 145         * zero, resulting in a kill(0), which will result in the
 146         * whole UML suddenly dying.  Also, cover negative and
 147         * 1 cases, since they shouldn't happen either.
 148         */
 149        if (mmu->id.u.pid < 2) {
 150                printk(KERN_ERR "corrupt mm_context - pid = %d\n",
 151                       mmu->id.u.pid);
 152                return;
 153        }
 154        os_kill_ptraced_process(mmu->id.u.pid, 1);
 155
 156        free_page(mmu->id.stack);
 157        free_ldt(mmu);
 158}
 159