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/signal.h>
   9#include <linux/slab.h>
  10
  11#include <asm/pgalloc.h>
  12#include <asm/pgtable.h>
  13#include <asm/sections.h>
  14#include <as-layout.h>
  15#include <os.h>
  16#include <skas.h>
  17
  18static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
  19                         unsigned long kernel)
  20{
  21        pgd_t *pgd;
  22        pud_t *pud;
  23        pmd_t *pmd;
  24        pte_t *pte;
  25
  26        pgd = pgd_offset(mm, proc);
  27        pud = pud_alloc(mm, pgd, proc);
  28        if (!pud)
  29                goto out;
  30
  31        pmd = pmd_alloc(mm, pud, proc);
  32        if (!pmd)
  33                goto out_pmd;
  34
  35        pte = pte_alloc_map(mm, pmd, proc);
  36        if (!pte)
  37                goto out_pte;
  38
  39        *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
  40        *pte = pte_mkread(*pte);
  41        return 0;
  42
  43 out_pte:
  44        pmd_free(mm, pmd);
  45 out_pmd:
  46        pud_free(mm, pud);
  47 out:
  48        return -ENOMEM;
  49}
  50
  51int init_new_context(struct task_struct *task, struct mm_struct *mm)
  52{
  53        struct mm_context *from_mm = NULL;
  54        struct mm_context *to_mm = &mm->context;
  55        unsigned long stack = 0;
  56        int ret = -ENOMEM;
  57
  58        stack = get_zeroed_page(GFP_KERNEL);
  59        if (stack == 0)
  60                goto out;
  61
  62        to_mm->id.stack = stack;
  63        if (current->mm != NULL && current->mm != &init_mm)
  64                from_mm = &current->mm->context;
  65
  66        block_signals();
  67        if (from_mm)
  68                to_mm->id.u.pid = copy_context_skas0(stack,
  69                                                     from_mm->id.u.pid);
  70        else to_mm->id.u.pid = start_userspace(stack);
  71        unblock_signals();
  72
  73        if (to_mm->id.u.pid < 0) {
  74                ret = to_mm->id.u.pid;
  75                goto out_free;
  76        }
  77
  78        ret = init_new_ldt(to_mm, from_mm);
  79        if (ret < 0) {
  80                printk(KERN_ERR "init_new_context_skas - init_ldt"
  81                       " failed, errno = %d\n", ret);
  82                goto out_free;
  83        }
  84
  85        return 0;
  86
  87 out_free:
  88        if (to_mm->id.stack != 0)
  89                free_page(to_mm->id.stack);
  90 out:
  91        return ret;
  92}
  93
  94void uml_setup_stubs(struct mm_struct *mm)
  95{
  96        int err, ret;
  97
  98        ret = init_stub_pte(mm, STUB_CODE,
  99                            (unsigned long) __syscall_stub_start);
 100        if (ret)
 101                goto out;
 102
 103        ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
 104        if (ret)
 105                goto out;
 106
 107        mm->context.stub_pages[0] = virt_to_page(__syscall_stub_start);
 108        mm->context.stub_pages[1] = virt_to_page(mm->context.id.stack);
 109
 110        /* dup_mmap already holds mmap_sem */
 111        err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
 112                                      VM_READ | VM_MAYREAD | VM_EXEC |
 113                                      VM_MAYEXEC | VM_DONTCOPY | VM_PFNMAP,
 114                                      mm->context.stub_pages);
 115        if (err) {
 116                printk(KERN_ERR "install_special_mapping returned %d\n", err);
 117                goto out;
 118        }
 119        return;
 120
 121out:
 122        force_sigsegv(SIGSEGV);
 123}
 124
 125void arch_exit_mmap(struct mm_struct *mm)
 126{
 127        pte_t *pte;
 128
 129        pte = virt_to_pte(mm, STUB_CODE);
 130        if (pte != NULL)
 131                pte_clear(mm, STUB_CODE, pte);
 132
 133        pte = virt_to_pte(mm, STUB_DATA);
 134        if (pte == NULL)
 135                return;
 136
 137        pte_clear(mm, STUB_DATA, pte);
 138}
 139
 140void destroy_context(struct mm_struct *mm)
 141{
 142        struct mm_context *mmu = &mm->context;
 143
 144        /*
 145         * If init_new_context wasn't called, this will be
 146         * zero, resulting in a kill(0), which will result in the
 147         * whole UML suddenly dying.  Also, cover negative and
 148         * 1 cases, since they shouldn't happen either.
 149         */
 150        if (mmu->id.u.pid < 2) {
 151                printk(KERN_ERR "corrupt mm_context - pid = %d\n",
 152                       mmu->id.u.pid);
 153                return;
 154        }
 155        os_kill_ptraced_process(mmu->id.u.pid, 1);
 156
 157        free_page(mmu->id.stack);
 158        free_ldt(mmu);
 159}
 160