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Diffstat (limited to 'arch/um/kernel/skas/mmu.c')
-rw-r--r--arch/um/kernel/skas/mmu.c104
1 files changed, 59 insertions, 45 deletions
diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index 6da9ab4f5a1..e8dc8540d44 100644
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -34,25 +34,6 @@ static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
if (!pte)
goto out_pte;
- /*
- * There's an interaction between the skas0 stub pages, stack
- * randomization, and the BUG at the end of exit_mmap. exit_mmap
- * checks that the number of page tables freed is the same as had
- * been allocated. If the stack is on the last page table page,
- * then the stack pte page will be freed, and if not, it won't. To
- * avoid having to know where the stack is, or if the process mapped
- * something at the top of its address space for some other reason,
- * we set TASK_SIZE to end at the start of the last page table.
- * This keeps exit_mmap off the last page, but introduces a leak
- * of that page. So, we hang onto it here and free it in
- * destroy_context_skas.
- */
-
- mm->context.last_page_table = pmd_page_vaddr(*pmd);
-#ifdef CONFIG_3_LEVEL_PGTABLES
- mm->context.last_pmd = (unsigned long) __va(pud_val(*pud));
-#endif
-
*pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
*pte = pte_mkread(*pte);
return 0;
@@ -76,24 +57,6 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
stack = get_zeroed_page(GFP_KERNEL);
if (stack == 0)
goto out;
-
- /*
- * This zeros the entry that pgd_alloc didn't, needed since
- * we are about to reinitialize it, and want mm.nr_ptes to
- * be accurate.
- */
- mm->pgd[USER_PTRS_PER_PGD] = __pgd(0);
-
- ret = init_stub_pte(mm, STUB_CODE,
- (unsigned long) &__syscall_stub_start);
- if (ret)
- goto out_free;
-
- ret = init_stub_pte(mm, STUB_DATA, stack);
- if (ret)
- goto out_free;
-
- mm->nr_ptes--;
}
to_mm->id.stack = stack;
@@ -137,6 +100,64 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
return ret;
}
+void arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
+{
+ struct page **pages;
+ int err, ret;
+
+ if (!skas_needs_stub)
+ return;
+
+ ret = init_stub_pte(mm, STUB_CODE,
+ (unsigned long) &__syscall_stub_start);
+ if (ret)
+ goto out;
+
+ ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
+ if (ret)
+ goto out;
+
+ pages = kmalloc(2 * sizeof(struct page *), GFP_KERNEL);
+ if (pages == NULL) {
+ printk(KERN_ERR "arch_dup_mmap failed to allocate 2 page "
+ "pointers\n");
+ goto out;
+ }
+
+ pages[0] = virt_to_page(&__syscall_stub_start);
+ pages[1] = virt_to_page(mm->context.id.stack);
+
+ /* dup_mmap already holds mmap_sem */
+ err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
+ VM_READ | VM_MAYREAD | VM_EXEC |
+ VM_MAYEXEC | VM_DONTCOPY, pages);
+ if (err) {
+ printk(KERN_ERR "install_special_mapping returned %d\n", err);
+ goto out_free;
+ }
+ return;
+
+out_free:
+ kfree(pages);
+out:
+ force_sigsegv(SIGSEGV, current);
+}
+
+void arch_exit_mmap(struct mm_struct *mm)
+{
+ pte_t *pte;
+
+ pte = virt_to_pte(mm, STUB_CODE);
+ if (pte != NULL)
+ pte_clear(mm, STUB_CODE, pte);
+
+ pte = virt_to_pte(mm, STUB_DATA);
+ if (pte == NULL)
+ return;
+
+ pte_clear(mm, STUB_DATA, pte);
+}
+
void destroy_context(struct mm_struct *mm)
{
struct mm_context *mmu = &mm->context;
@@ -146,15 +167,8 @@ void destroy_context(struct mm_struct *mm)
else
os_kill_ptraced_process(mmu->id.u.pid, 1);
- if (!proc_mm || !ptrace_faultinfo) {
+ if (skas_needs_stub)
free_page(mmu->id.stack);
- pte_lock_deinit(virt_to_page(mmu->last_page_table));
- pte_free_kernel(mm, (pte_t *) mmu->last_page_table);
- dec_zone_page_state(virt_to_page(mmu->last_page_table), NR_PAGETABLE);
-#ifdef CONFIG_3_LEVEL_PGTABLES
- pmd_free(mm, (pmd_t *) mmu->last_pmd);
-#endif
- }
free_ldt(mmu);
}