1 files changed, 250 insertions, 0 deletions
diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
new file mode 100644
index 000000000..f9da5b149
--- /dev/null
+++ b/arch/s390/kernel/vdso.c
@@ -0,0 +1,250 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * vdso setup for s390
+ *
+ *  Copyright IBM Corp. 2008
+ *  Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
+ */
+
+#include <linux/init.h>
+#include <linux/errno.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/stddef.h>
+#include <linux/unistd.h>
+#include <linux/slab.h>
+#include <linux/user.h>
+#include <linux/elf.h>
+#include <linux/security.h>
+#include <linux/memblock.h>
+#include <linux/compat.h>
+#include <linux/binfmts.h>
+#include <vdso/datapage.h>
+#include <asm/asm-offsets.h>
+#include <asm/processor.h>
+#include <asm/mmu.h>
+#include <asm/mmu_context.h>
+#include <asm/sections.h>
+#include <asm/vdso.h>
+#include <asm/facility.h>
+
+extern char vdso64_start, vdso64_end;
+static void *vdso64_kbase = &vdso64_start;
+static unsigned int vdso64_pages;
+static struct page **vdso64_pagelist;
+
+/*
+ * Should the kernel map a VDSO page into processes and pass its
+ * address down to glibc upon exec()?
+ */
+unsigned int __read_mostly vdso_enabled = 1;
+
+static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
+		      struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+	struct page **vdso_pagelist;
+	unsigned long vdso_pages;
+
+	vdso_pagelist = vdso64_pagelist;
+	vdso_pages = vdso64_pages;
+
+	if (vmf->pgoff >= vdso_pages)
+		return VM_FAULT_SIGBUS;
+
+	vmf->page = vdso_pagelist[vmf->pgoff];
+	get_page(vmf->page);
+	return 0;
+}
+
+static int vdso_mremap(const struct vm_special_mapping *sm,
+		       struct vm_area_struct *vma)
+{
+	unsigned long vdso_pages;
+
+	vdso_pages = vdso64_pages;
+
+	if ((vdso_pages << PAGE_SHIFT) != vma->vm_end - vma->vm_start)
+		return -EINVAL;
+
+	if (WARN_ON_ONCE(current->mm != vma->vm_mm))
+		return -EFAULT;
+
+	current->mm->context.vdso_base = vma->vm_start;
+	return 0;
+}
+
+static const struct vm_special_mapping vdso_mapping = {
+	.name = "[vdso]",
+	.fault = vdso_fault,
+	.mremap = vdso_mremap,
+};
+
+static int __init vdso_setup(char *str)
+{
+	bool enabled;
+
+	if (!kstrtobool(str, &enabled))
+		vdso_enabled = enabled;
+	return 1;
+}
+__setup("vdso=", vdso_setup);
+
+/*
+ * The vdso data page
+ */
+static union {
+	struct vdso_data	data;
+	u8			page[PAGE_SIZE];
+} vdso_data_store __page_aligned_data;
+struct vdso_data *vdso_data = (struct vdso_data *)&vdso_data_store.data;
+/*
+ * Allocate/free per cpu vdso data.
+ */
+#define SEGMENT_ORDER	2
+
+int vdso_alloc_per_cpu(struct lowcore *lowcore)
+{
+	unsigned long segment_table, page_table, page_frame;
+	struct vdso_per_cpu_data *vd;
+
+	segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
+	page_table = get_zeroed_page(GFP_KERNEL);
+	page_frame = get_zeroed_page(GFP_KERNEL);
+	if (!segment_table || !page_table || !page_frame)
+		goto out;
+	arch_set_page_dat(virt_to_page(segment_table), SEGMENT_ORDER);
+	arch_set_page_dat(virt_to_page(page_table), 0);
+
+	/* Initialize per-cpu vdso data page */
+	vd = (struct vdso_per_cpu_data *) page_frame;
+	vd->cpu_nr = lowcore->cpu_nr;
+	vd->node_id = cpu_to_node(vd->cpu_nr);
+
+	/* Set up page table for the vdso address space */
+	memset64((u64 *)segment_table, _SEGMENT_ENTRY_EMPTY, _CRST_ENTRIES);
+	memset64((u64 *)page_table, _PAGE_INVALID, PTRS_PER_PTE);
+
+	*(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
+	*(unsigned long *) page_table = _PAGE_PROTECT + page_frame;
+
+	lowcore->vdso_asce = segment_table +
+		_ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
+	lowcore->vdso_per_cpu_data = page_frame;
+
+	return 0;
+
+out:
+	free_page(page_frame);
+	free_page(page_table);
+	free_pages(segment_table, SEGMENT_ORDER);
+	return -ENOMEM;
+}
+
+void vdso_free_per_cpu(struct lowcore *lowcore)
+{
+	unsigned long segment_table, page_table, page_frame;
+
+	segment_table = lowcore->vdso_asce & PAGE_MASK;
+	page_table = *(unsigned long *) segment_table;
+	page_frame = *(unsigned long *) page_table;
+
+	free_page(page_frame);
+	free_page(page_table);
+	free_pages(segment_table, SEGMENT_ORDER);
+}
+
+/*
+ * This is called from binfmt_elf, we create the special vma for the
+ * vDSO and insert it into the mm struct tree
+ */
+int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	unsigned long vdso_pages;
+	unsigned long vdso_base;
+	int rc;
+
+	if (!vdso_enabled)
+		return 0;
+
+	if (is_compat_task())
+		return 0;
+
+	vdso_pages = vdso64_pages;
+	/*
+	 * vDSO has a problem and was disabled, just don't "enable" it for
+	 * the process
+	 */
+	if (vdso_pages == 0)
+		return 0;
+
+	/*
+	 * pick a base address for the vDSO in process space. We try to put
+	 * it at vdso_base which is the "natural" base for it, but we might
+	 * fail and end up putting it elsewhere.
+	 */
+	if (mmap_write_lock_killable(mm))
+		return -EINTR;
+	vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
+	if (IS_ERR_VALUE(vdso_base)) {
+		rc = vdso_base;
+		goto out_up;
+	}
+
+	/*
+	 * our vma flags don't have VM_WRITE so by default, the process
+	 * isn't allowed to write those pages.
+	 * gdb can break that with ptrace interface, and thus trigger COW
+	 * on those pages but it's then your responsibility to never do that
+	 * on the "data" page of the vDSO or you'll stop getting kernel
+	 * updates and your nice userland gettimeofday will be totally dead.
+	 * It's fine to use that for setting breakpoints in the vDSO code
+	 * pages though.
+	 */
+	vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
+				       VM_READ|VM_EXEC|
+				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
+				       &vdso_mapping);
+	if (IS_ERR(vma)) {
+		rc = PTR_ERR(vma);
+		goto out_up;
+	}
+
+	current->mm->context.vdso_base = vdso_base;
+	rc = 0;
+
+out_up:
+	mmap_write_unlock(mm);
+	return rc;
+}
+
+static int __init vdso_init(void)
+{
+	int i;
+
+	/* Calculate the size of the 64 bit vDSO */
+	vdso64_pages = ((&vdso64_end - &vdso64_start
+			 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
+
+	/* Make sure pages are in the correct state */
+	vdso64_pagelist = kcalloc(vdso64_pages + 1, sizeof(struct page *),
+				  GFP_KERNEL);
+	BUG_ON(vdso64_pagelist == NULL);
+	for (i = 0; i < vdso64_pages - 1; i++) {
+		struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
+		get_page(pg);
+		vdso64_pagelist[i] = pg;
+	}
+	vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
+	vdso64_pagelist[vdso64_pages] = NULL;
+	if (vdso_alloc_per_cpu(&S390_lowcore))
+		BUG();
+
+	get_page(virt_to_page(vdso_data));
+
+	return 0;
+}
+early_initcall(vdso_init);