1 /* 2 * vDSO implementation for Hexagon 3 * 4 * Copyright (c) 2011, The Linux Foundation. All rights reserved. 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 and 8 * only version 2 as published by the Free Software Foundation. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, write to the Free Software 17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 18 * 02110-1301, USA. 19 */ 20 21 #include <linux/err.h> 22 #include <linux/mm.h> 23 #include <linux/vmalloc.h> 24 #include <linux/binfmts.h> 25 26 #include <asm/vdso.h> 27 28 static struct page *vdso_page; 29 30 /* Create a vDSO page holding the signal trampoline. 31 * We want this for a non-executable stack. 32 */ 33 static int __init vdso_init(void) 34 { 35 struct hexagon_vdso *vdso; 36 37 vdso_page = alloc_page(GFP_KERNEL); 38 if (!vdso_page) 39 panic("Cannot allocate vdso"); 40 41 vdso = vmap(&vdso_page, 1, 0, PAGE_KERNEL); 42 if (!vdso) 43 panic("Cannot map vdso"); 44 clear_page(vdso); 45 46 /* Install the signal trampoline; currently looks like this: 47 * r6 = #__NR_rt_sigreturn; 48 * trap0(#1); 49 */ 50 vdso->rt_signal_trampoline[0] = __rt_sigtramp_template[0]; 51 vdso->rt_signal_trampoline[1] = __rt_sigtramp_template[1]; 52 53 vunmap(vdso); 54 55 return 0; 56 } 57 arch_initcall(vdso_init); 58 59 /* 60 * Called from binfmt_elf. Create a VMA for the vDSO page. 61 */ 62 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 63 { 64 int ret; 65 unsigned long vdso_base; 66 struct mm_struct *mm = current->mm; 67 68 down_write(&mm->mmap_sem); 69 70 /* Try to get it loaded right near ld.so/glibc. */ 71 vdso_base = STACK_TOP; 72 73 vdso_base = get_unmapped_area(NULL, vdso_base, PAGE_SIZE, 0, 0); 74 if (IS_ERR_VALUE(vdso_base)) { 75 ret = vdso_base; 76 goto up_fail; 77 } 78 79 /* MAYWRITE to allow gdb to COW and set breakpoints. */ 80 ret = install_special_mapping(mm, vdso_base, PAGE_SIZE, 81 VM_READ|VM_EXEC| 82 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 83 &vdso_page); 84 85 if (ret) 86 goto up_fail; 87 88 mm->context.vdso = (void *)vdso_base; 89 90 up_fail: 91 up_write(&mm->mmap_sem); 92 return ret; 93 } 94 95 const char *arch_vma_name(struct vm_area_struct *vma) 96 { 97 if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso) 98 return "[vdso]"; 99 return NULL; 100 } 101