1 files changed, 280 insertions, 0 deletions
diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
new file mode 100644
index 000000000..3105ca5bd
--- /dev/null
+++ b/arch/s390/kernel/vdso.c
@@ -0,0 +1,280 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * vdso setup for s390
+ *
+ *  Copyright IBM Corp. 2008
+ *  Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
+ */
+
+#include <linux/binfmts.h>
+#include <linux/compat.h>
+#include <linux/elf.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/smp.h>
+#include <linux/time_namespace.h>
+#include <linux/random.h>
+#include <vdso/datapage.h>
+#include <asm/vdso.h>
+
+extern char vdso64_start[], vdso64_end[];
+extern char vdso32_start[], vdso32_end[];
+
+static struct vm_special_mapping vvar_mapping;
+
+static union {
+	struct vdso_data	data[CS_BASES];
+	u8			page[PAGE_SIZE];
+} vdso_data_store __page_aligned_data;
+
+struct vdso_data *vdso_data = vdso_data_store.data;
+
+enum vvar_pages {
+	VVAR_DATA_PAGE_OFFSET,
+	VVAR_TIMENS_PAGE_OFFSET,
+	VVAR_NR_PAGES,
+};
+
+#ifdef CONFIG_TIME_NS
+struct vdso_data *arch_get_vdso_data(void *vvar_page)
+{
+	return (struct vdso_data *)(vvar_page);
+}
+
+static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
+{
+	if (likely(vma->vm_mm == current->mm))
+		return current->nsproxy->time_ns->vvar_page;
+	/*
+	 * VM_PFNMAP | VM_IO protect .fault() handler from being called
+	 * through interfaces like /proc/$pid/mem or
+	 * process_vm_{readv,writev}() as long as there's no .access()
+	 * in special_mapping_vmops().
+	 * For more details check_vma_flags() and __access_remote_vm()
+	 */
+	WARN(1, "vvar_page accessed remotely");
+	return NULL;
+}
+
+/*
+ * The VVAR page layout depends on whether a task belongs to the root or
+ * non-root time namespace. Whenever a task changes its namespace, the VVAR
+ * page tables are cleared and then they will be re-faulted with a
+ * corresponding layout.
+ * See also the comment near timens_setup_vdso_data() for details.
+ */
+int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
+{
+	struct mm_struct *mm = task->mm;
+	VMA_ITERATOR(vmi, mm, 0);
+	struct vm_area_struct *vma;
+
+	mmap_read_lock(mm);
+	for_each_vma(vmi, vma) {
+		unsigned long size = vma->vm_end - vma->vm_start;
+
+		if (!vma_is_special_mapping(vma, &vvar_mapping))
+			continue;
+		zap_page_range(vma, vma->vm_start, size);
+		break;
+	}
+	mmap_read_unlock(mm);
+	return 0;
+}
+#else
+static inline struct page *find_timens_vvar_page(struct vm_area_struct *vma)
+{
+	return NULL;
+}
+#endif
+
+static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
+			     struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+	struct page *timens_page = find_timens_vvar_page(vma);
+	unsigned long addr, pfn;
+	vm_fault_t err;
+
+	switch (vmf->pgoff) {
+	case VVAR_DATA_PAGE_OFFSET:
+		pfn = virt_to_pfn(vdso_data);
+		if (timens_page) {
+			/*
+			 * Fault in VVAR page too, since it will be accessed
+			 * to get clock data anyway.
+			 */
+			addr = vmf->address + VVAR_TIMENS_PAGE_OFFSET * PAGE_SIZE;
+			err = vmf_insert_pfn(vma, addr, pfn);
+			if (unlikely(err & VM_FAULT_ERROR))
+				return err;
+			pfn = page_to_pfn(timens_page);
+		}
+		break;
+#ifdef CONFIG_TIME_NS
+	case VVAR_TIMENS_PAGE_OFFSET:
+		/*
+		 * If a task belongs to a time namespace then a namespace
+		 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
+		 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
+		 * offset.
+		 * See also the comment near timens_setup_vdso_data().
+		 */
+		if (!timens_page)
+			return VM_FAULT_SIGBUS;
+		pfn = virt_to_pfn(vdso_data);
+		break;
+#endif /* CONFIG_TIME_NS */
+	default:
+		return VM_FAULT_SIGBUS;
+	}
+	return vmf_insert_pfn(vma, vmf->address, pfn);
+}
+
+static int vdso_mremap(const struct vm_special_mapping *sm,
+		       struct vm_area_struct *vma)
+{
+	current->mm->context.vdso_base = vma->vm_start;
+	return 0;
+}
+
+static struct vm_special_mapping vvar_mapping = {
+	.name = "[vvar]",
+	.fault = vvar_fault,
+};
+
+static struct vm_special_mapping vdso64_mapping = {
+	.name = "[vdso]",
+	.mremap = vdso_mremap,
+};
+
+static struct vm_special_mapping vdso32_mapping = {
+	.name = "[vdso]",
+	.mremap = vdso_mremap,
+};
+
+int vdso_getcpu_init(void)
+{
+	set_tod_programmable_field(smp_processor_id());
+	return 0;
+}
+early_initcall(vdso_getcpu_init); /* Must be called before SMP init */
+
+static int map_vdso(unsigned long addr, unsigned long vdso_mapping_len)
+{
+	unsigned long vvar_start, vdso_text_start, vdso_text_len;
+	struct vm_special_mapping *vdso_mapping;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	int rc;
+
+	BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
+	if (mmap_write_lock_killable(mm))
+		return -EINTR;
+
+	if (is_compat_task()) {
+		vdso_text_len = vdso32_end - vdso32_start;
+		vdso_mapping = &vdso32_mapping;
+	} else {
+		vdso_text_len = vdso64_end - vdso64_start;
+		vdso_mapping = &vdso64_mapping;
+	}
+	vvar_start = get_unmapped_area(NULL, addr, vdso_mapping_len, 0, 0);
+	rc = vvar_start;
+	if (IS_ERR_VALUE(vvar_start))
+		goto out;
+	vma = _install_special_mapping(mm, vvar_start, VVAR_NR_PAGES*PAGE_SIZE,
+				       VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
+				       VM_PFNMAP,
+				       &vvar_mapping);
+	rc = PTR_ERR(vma);
+	if (IS_ERR(vma))
+		goto out;
+	vdso_text_start = vvar_start + VVAR_NR_PAGES * PAGE_SIZE;
+	/* VM_MAYWRITE for COW so gdb can set breakpoints */
+	vma = _install_special_mapping(mm, vdso_text_start, vdso_text_len,
+				       VM_READ|VM_EXEC|
+				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
+				       vdso_mapping);
+	if (IS_ERR(vma)) {
+		do_munmap(mm, vvar_start, PAGE_SIZE, NULL);
+		rc = PTR_ERR(vma);
+	} else {
+		current->mm->context.vdso_base = vdso_text_start;
+		rc = 0;
+	}
+out:
+	mmap_write_unlock(mm);
+	return rc;
+}
+
+static unsigned long vdso_addr(unsigned long start, unsigned long len)
+{
+	unsigned long addr, end, offset;
+
+	/*
+	 * Round up the start address. It can start out unaligned as a result
+	 * of stack start randomization.
+	 */
+	start = PAGE_ALIGN(start);
+
+	/* Round the lowest possible end address up to a PMD boundary. */
+	end = (start + len + PMD_SIZE - 1) & PMD_MASK;
+	if (end >= VDSO_BASE)
+		end = VDSO_BASE;
+	end -= len;
+
+	if (end > start) {
+		offset = prandom_u32_max(((end - start) >> PAGE_SHIFT) + 1);
+		addr = start + (offset << PAGE_SHIFT);
+	} else {
+		addr = start;
+	}
+	return addr;
+}
+
+unsigned long vdso_size(void)
+{
+	unsigned long size = VVAR_NR_PAGES * PAGE_SIZE;
+
+	if (is_compat_task())
+		size += vdso32_end - vdso32_start;
+	else
+		size += vdso64_end - vdso64_start;
+	return PAGE_ALIGN(size);
+}
+
+int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+{
+	unsigned long addr = VDSO_BASE;
+	unsigned long size = vdso_size();
+
+	if (current->flags & PF_RANDOMIZE)
+		addr = vdso_addr(current->mm->start_stack + PAGE_SIZE, size);
+	return map_vdso(addr, size);
+}
+
+static struct page ** __init vdso_setup_pages(void *start, void *end)
+{
+	int pages = (end - start) >> PAGE_SHIFT;
+	struct page **pagelist;
+	int i;
+
+	pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL);
+	if (!pagelist)
+		panic("%s: Cannot allocate page list for VDSO", __func__);
+	for (i = 0; i < pages; i++)
+		pagelist[i] = virt_to_page(start + i * PAGE_SIZE);
+	return pagelist;
+}
+
+static int __init vdso_init(void)
+{
+	vdso64_mapping.pages = vdso_setup_pages(vdso64_start, vdso64_end);
+	if (IS_ENABLED(CONFIG_COMPAT))
+		vdso32_mapping.pages = vdso_setup_pages(vdso32_start, vdso32_end);
+	return 0;
+}
+arch_initcall(vdso_init);