fc5243d98a
arch_setup_additional_pages currently gets two arguments, the binary format descripton and an indication if the process uses an executable stack or not. The second argument is not used by anybody, it could be removed without replacement. What actually does make sense is to pass an indication if the process uses the elf interpreter or not. The glibc code will not use anything from the vdso if the process does not use the dynamic linker, so for statically linked binaries the architecture backend can choose not to map the vdso. Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
138 lines
3.1 KiB
C
138 lines
3.1 KiB
C
/*
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* Set up the VMAs to tell the VM about the vDSO.
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* Copyright 2007 Andi Kleen, SUSE Labs.
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* Subject to the GPL, v.2
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*/
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#include <linux/mm.h>
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#include <linux/err.h>
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#include <linux/sched.h>
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#include <linux/init.h>
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#include <linux/random.h>
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#include <asm/vsyscall.h>
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#include <asm/vgtod.h>
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#include <asm/proto.h>
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#include <asm/vdso.h>
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#include "vextern.h" /* Just for VMAGIC. */
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#undef VEXTERN
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unsigned int __read_mostly vdso_enabled = 1;
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extern char vdso_start[], vdso_end[];
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extern unsigned short vdso_sync_cpuid;
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static struct page **vdso_pages;
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static unsigned vdso_size;
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static inline void *var_ref(void *p, char *name)
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{
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if (*(void **)p != (void *)VMAGIC) {
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printk("VDSO: variable %s broken\n", name);
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vdso_enabled = 0;
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}
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return p;
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}
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static int __init init_vdso_vars(void)
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{
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int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE;
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int i;
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char *vbase;
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vdso_size = npages << PAGE_SHIFT;
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vdso_pages = kmalloc(sizeof(struct page *) * npages, GFP_KERNEL);
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if (!vdso_pages)
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goto oom;
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for (i = 0; i < npages; i++) {
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struct page *p;
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p = alloc_page(GFP_KERNEL);
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if (!p)
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goto oom;
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vdso_pages[i] = p;
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copy_page(page_address(p), vdso_start + i*PAGE_SIZE);
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}
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vbase = vmap(vdso_pages, npages, 0, PAGE_KERNEL);
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if (!vbase)
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goto oom;
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if (memcmp(vbase, "\177ELF", 4)) {
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printk("VDSO: I'm broken; not ELF\n");
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vdso_enabled = 0;
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}
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#define VEXTERN(x) \
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*(typeof(__ ## x) **) var_ref(VDSO64_SYMBOL(vbase, x), #x) = &__ ## x;
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#include "vextern.h"
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#undef VEXTERN
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return 0;
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oom:
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printk("Cannot allocate vdso\n");
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vdso_enabled = 0;
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return -ENOMEM;
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}
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__initcall(init_vdso_vars);
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struct linux_binprm;
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/* Put the vdso above the (randomized) stack with another randomized offset.
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This way there is no hole in the middle of address space.
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To save memory make sure it is still in the same PTE as the stack top.
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This doesn't give that many random bits */
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static unsigned long vdso_addr(unsigned long start, unsigned len)
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{
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unsigned long addr, end;
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unsigned offset;
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end = (start + PMD_SIZE - 1) & PMD_MASK;
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if (end >= TASK_SIZE64)
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end = TASK_SIZE64;
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end -= len;
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/* This loses some more bits than a modulo, but is cheaper */
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offset = get_random_int() & (PTRS_PER_PTE - 1);
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addr = start + (offset << PAGE_SHIFT);
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if (addr >= end)
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addr = end;
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return addr;
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}
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/* Setup a VMA at program startup for the vsyscall page.
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Not called for compat tasks */
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int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
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{
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struct mm_struct *mm = current->mm;
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unsigned long addr;
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int ret;
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if (!vdso_enabled)
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return 0;
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down_write(&mm->mmap_sem);
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addr = vdso_addr(mm->start_stack, vdso_size);
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addr = get_unmapped_area(NULL, addr, vdso_size, 0, 0);
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if (IS_ERR_VALUE(addr)) {
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ret = addr;
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goto up_fail;
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}
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ret = install_special_mapping(mm, addr, vdso_size,
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VM_READ|VM_EXEC|
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VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
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VM_ALWAYSDUMP,
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vdso_pages);
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if (ret)
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goto up_fail;
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current->mm->context.vdso = (void *)addr;
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up_fail:
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up_write(&mm->mmap_sem);
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return ret;
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}
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static __init int vdso_setup(char *s)
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{
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vdso_enabled = simple_strtoul(s, NULL, 0);
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return 0;
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}
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__setup("vdso=", vdso_setup);
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