1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de) 4 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) 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/sections.h> 13 #include <as-layout.h> 14 #include <os.h> 15 #include <skas.h> 16 17 static int init_stub_pte(struct mm_struct *mm, unsigned long proc, 18 unsigned long kernel) 19 { 20 pgd_t *pgd; 21 p4d_t *p4d; 22 pud_t *pud; 23 pmd_t *pmd; 24 pte_t *pte; 25 26 pgd = pgd_offset(mm, proc); 27 28 p4d = p4d_alloc(mm, pgd, proc); 29 if (!p4d) 30 goto out; 31 32 pud = pud_alloc(mm, p4d, proc); 33 if (!pud) 34 goto out_pud; 35 36 pmd = pmd_alloc(mm, pud, proc); 37 if (!pmd) 38 goto out_pmd; 39 40 pte = pte_alloc_map(mm, pmd, proc); 41 if (!pte) 42 goto out_pte; 43 44 *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT)); 45 *pte = pte_mkread(*pte); 46 return 0; 47 48 out_pte: 49 pmd_free(mm, pmd); 50 out_pmd: 51 pud_free(mm, pud); 52 out_pud: 53 p4d_free(mm, p4d); 54 out: 55 return -ENOMEM; 56 } 57 58 int init_new_context(struct task_struct *task, struct mm_struct *mm) 59 { 60 struct mm_context *from_mm = NULL; 61 struct mm_context *to_mm = &mm->context; 62 unsigned long stack = 0; 63 int ret = -ENOMEM; 64 65 stack = get_zeroed_page(GFP_KERNEL); 66 if (stack == 0) 67 goto out; 68 69 to_mm->id.stack = stack; 70 if (current->mm != NULL && current->mm != &init_mm) 71 from_mm = ¤t->mm->context; 72 73 block_signals_trace(); 74 if (from_mm) 75 to_mm->id.u.pid = copy_context_skas0(stack, 76 from_mm->id.u.pid); 77 else to_mm->id.u.pid = start_userspace(stack); 78 unblock_signals_trace(); 79 80 if (to_mm->id.u.pid < 0) { 81 ret = to_mm->id.u.pid; 82 goto out_free; 83 } 84 85 ret = init_new_ldt(to_mm, from_mm); 86 if (ret < 0) { 87 printk(KERN_ERR "init_new_context_skas - init_ldt" 88 " failed, errno = %d\n", ret); 89 goto out_free; 90 } 91 92 return 0; 93 94 out_free: 95 if (to_mm->id.stack != 0) 96 free_page(to_mm->id.stack); 97 out: 98 return ret; 99 } 100 101 void uml_setup_stubs(struct mm_struct *mm) 102 { 103 int err, ret; 104 105 ret = init_stub_pte(mm, STUB_CODE, 106 (unsigned long) __syscall_stub_start); 107 if (ret) 108 goto out; 109 110 ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack); 111 if (ret) 112 goto out; 113 114 mm->context.stub_pages[0] = virt_to_page(__syscall_stub_start); 115 mm->context.stub_pages[1] = virt_to_page(mm->context.id.stack); 116 117 /* dup_mmap already holds mmap_lock */ 118 err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START, 119 VM_READ | VM_MAYREAD | VM_EXEC | 120 VM_MAYEXEC | VM_DONTCOPY | VM_PFNMAP, 121 mm->context.stub_pages); 122 if (err) { 123 printk(KERN_ERR "install_special_mapping returned %d\n", err); 124 goto out; 125 } 126 return; 127 128 out: 129 force_sigsegv(SIGSEGV); 130 } 131 132 void arch_exit_mmap(struct mm_struct *mm) 133 { 134 pte_t *pte; 135 136 pte = virt_to_pte(mm, STUB_CODE); 137 if (pte != NULL) 138 pte_clear(mm, STUB_CODE, pte); 139 140 pte = virt_to_pte(mm, STUB_DATA); 141 if (pte == NULL) 142 return; 143 144 pte_clear(mm, STUB_DATA, pte); 145 } 146 147 void destroy_context(struct mm_struct *mm) 148 { 149 struct mm_context *mmu = &mm->context; 150 151 /* 152 * If init_new_context wasn't called, this will be 153 * zero, resulting in a kill(0), which will result in the 154 * whole UML suddenly dying. Also, cover negative and 155 * 1 cases, since they shouldn't happen either. 156 */ 157 if (mmu->id.u.pid < 2) { 158 printk(KERN_ERR "corrupt mm_context - pid = %d\n", 159 mmu->id.u.pid); 160 return; 161 } 162 os_kill_ptraced_process(mmu->id.u.pid, 1); 163 164 free_page(mmu->id.stack); 165 free_ldt(mmu); 166 } 167