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 */ 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 */ 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 (down_write_killable(&mm->mmap_sem)) 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 up_write(&mm->mmap_sem); 80 return ret; 81 } 82 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