1 files changed, 116 insertions, 0 deletions
diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c
new file mode 100644
index 00000000..7abd2be0
--- /dev/null
+++ b/arch/x86/vdso/vma.c
@@ -0,0 +1,116 @@
+/*
+ * Set up the VMAs to tell the VM about the vDSO.
+ * Copyright 2007 Andi Kleen, SUSE Labs.
+ * Subject to the GPL, v.2
+ */
+#include <linux/mm.h>
+#include <linux/err.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/random.h>
+#include <linux/elf.h>
+#include <asm/vsyscall.h>
+#include <asm/vgtod.h>
+#include <asm/proto.h>
+#include <asm/vdso.h>
+
+unsigned int __read_mostly vdso_enabled = 1;
+
+extern char vdso_start[], vdso_end[];
+extern unsigned short vdso_sync_cpuid;
+
+static struct page **vdso_pages;
+static unsigned vdso_size;
+
+static int __init init_vdso_vars(void)
+{
+	int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE;
+	int i;
+
+	vdso_size = npages << PAGE_SHIFT;
+	vdso_pages = kmalloc(sizeof(struct page *) * npages, GFP_KERNEL);
+	if (!vdso_pages)
+		goto oom;
+	for (i = 0; i < npages; i++) {
+		struct page *p;
+		p = alloc_page(GFP_KERNEL);
+		if (!p)
+			goto oom;
+		vdso_pages[i] = p;
+		copy_page(page_address(p), vdso_start + i*PAGE_SIZE);
+	}
+
+	return 0;
+
+ oom:
+	printk("Cannot allocate vdso\n");
+	vdso_enabled = 0;
+	return -ENOMEM;
+}
+subsys_initcall(init_vdso_vars);
+
+struct linux_binprm;
+
+/* Put the vdso above the (randomized) stack with another randomized offset.
+   This way there is no hole in the middle of address space.
+   To save memory make sure it is still in the same PTE as the stack top.
+   This doesn't give that many random bits */
+static unsigned long vdso_addr(unsigned long start, unsigned len)
+{
+	unsigned long addr, end;
+	unsigned offset;
+	end = (start + PMD_SIZE - 1) & PMD_MASK;
+	if (end >= TASK_SIZE_MAX)
+		end = TASK_SIZE_MAX;
+	end -= len;
+	/* This loses some more bits than a modulo, but is cheaper */
+	offset = get_random_int() & (PTRS_PER_PTE - 1);
+	addr = start + (offset << PAGE_SHIFT);
+	if (addr >= end)
+		addr = end;
+	return addr;
+}
+
+/* Setup a VMA at program startup for the vsyscall page.
+   Not called for compat tasks */
+int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+{
+	struct mm_struct *mm = current->mm;
+	unsigned long addr;
+	int ret;
+
+	if (!vdso_enabled)
+		return 0;
+
+	down_write(&mm->mmap_sem);
+	addr = vdso_addr(mm->start_stack, vdso_size);
+	addr = get_unmapped_area(NULL, addr, vdso_size, 0, 0);
+	if (IS_ERR_VALUE(addr)) {
+		ret = addr;
+		goto up_fail;
+	}
+
+	current->mm->context.vdso = (void *)addr;
+
+	ret = install_special_mapping(mm, addr, vdso_size,
+				      VM_READ|VM_EXEC|
+				      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
+				      VM_ALWAYSDUMP,
+				      vdso_pages);
+	if (ret) {
+		current->mm->context.vdso = NULL;
+		goto up_fail;
+	}
+
+up_fail:
+	up_write(&mm->mmap_sem);
+	return ret;
+}
+
+static __init int vdso_setup(char *s)
+{
+	vdso_enabled = simple_strtoul(s, NULL, 0);
+	return 0;
+}
+__setup("vdso=", vdso_setup);