1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * vDSO implementation for Hexagon
4 *
5 * Copyright (c) 2011, The Linux Foundation. All rights reserved.
6 */
7
8 #include <linux/err.h>
9 #include <linux/mm.h>
10 #include <linux/vmalloc.h>
11 #include <linux/binfmts.h>
12
13 #include <asm/vdso.h>
14
15 static struct page *vdso_page;
16
17 /* Create a vDSO page holding the signal trampoline.
18 * We want this for a non-executable stack.
19 */
vdso_init(void)20 static int __init vdso_init(void)
21 {
22 struct hexagon_vdso *vdso;
23
24 vdso_page = alloc_page(GFP_KERNEL);
25 if (!vdso_page)
26 panic("Cannot allocate vdso");
27
28 vdso = vmap(&vdso_page, 1, 0, PAGE_KERNEL);
29 if (!vdso)
30 panic("Cannot map vdso");
31 clear_page(vdso);
32
33 /* Install the signal trampoline; currently looks like this:
34 * r6 = #__NR_rt_sigreturn;
35 * trap0(#1);
36 */
37 vdso->rt_signal_trampoline[0] = __rt_sigtramp_template[0];
38 vdso->rt_signal_trampoline[1] = __rt_sigtramp_template[1];
39
40 vunmap(vdso);
41
42 return 0;
43 }
44 arch_initcall(vdso_init);
45
46 /*
47 * Called from binfmt_elf. Create a VMA for the vDSO page.
48 */
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)49 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
50 {
51 int ret;
52 unsigned long vdso_base;
53 struct mm_struct *mm = current->mm;
54
55 if (mmap_write_lock_killable(mm))
56 return -EINTR;
57
58 /* Try to get it loaded right near ld.so/glibc. */
59 vdso_base = STACK_TOP;
60
61 vdso_base = get_unmapped_area(NULL, vdso_base, PAGE_SIZE, 0, 0);
62 if (IS_ERR_VALUE(vdso_base)) {
63 ret = vdso_base;
64 goto up_fail;
65 }
66
67 /* MAYWRITE to allow gdb to COW and set breakpoints. */
68 ret = install_special_mapping(mm, vdso_base, PAGE_SIZE,
69 VM_READ|VM_EXEC|
70 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
71 &vdso_page);
72
73 if (ret)
74 goto up_fail;
75
76 mm->context.vdso = (void *)vdso_base;
77
78 up_fail:
79 mmap_write_unlock(mm);
80 return ret;
81 }
82
arch_vma_name(struct vm_area_struct * vma)83 const char *arch_vma_name(struct vm_area_struct *vma)
84 {
85 if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
86 return "[vdso]";
87 return NULL;
88 }
89