1 /* 2 * vDSO implementation for Hexagon 3 * 4 * Copyright (c) 2011, Code Aurora Forum. 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 25 #include <asm/vdso.h> 26 27 static struct page *vdso_page; 28 29 /* Create a vDSO page holding the signal trampoline. 30 * We want this for a non-executable stack. 31 */ 32 static int __init vdso_init(void) 33 { 34 struct hexagon_vdso *vdso; 35 36 vdso_page = alloc_page(GFP_KERNEL); 37 if (!vdso_page) 38 panic("Cannot allocate vdso"); 39 40 vdso = vmap(&vdso_page, 1, 0, PAGE_KERNEL); 41 if (!vdso) 42 panic("Cannot map vdso"); 43 clear_page(vdso); 44 45 /* Install the signal trampoline; currently looks like this: 46 * r6 = #__NR_rt_sigreturn; 47 * trap0(#1); 48 */ 49 vdso->rt_signal_trampoline[0] = __rt_sigtramp_template[0]; 50 vdso->rt_signal_trampoline[1] = __rt_sigtramp_template[1]; 51 52 vunmap(vdso); 53 54 return 0; 55 } 56 arch_initcall(vdso_init); 57 58 /* 59 * Called from binfmt_elf. Create a VMA for the vDSO page. 60 */ 61 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 62 { 63 int ret; 64 unsigned long vdso_base; 65 struct mm_struct *mm = current->mm; 66 67 down_write(&mm->mmap_sem); 68 69 /* Try to get it loaded right near ld.so/glibc. */ 70 vdso_base = STACK_TOP; 71 72 vdso_base = get_unmapped_area(NULL, vdso_base, PAGE_SIZE, 0, 0); 73 if (IS_ERR_VALUE(vdso_base)) { 74 ret = vdso_base; 75 goto up_fail; 76 } 77 78 /* MAYWRITE to allow gdb to COW and set breakpoints. */ 79 ret = install_special_mapping(mm, vdso_base, PAGE_SIZE, 80 VM_READ|VM_EXEC| 81 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| 82 VM_ALWAYSDUMP, 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