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authorHeiko Carstens2021-02-05 16:19:32 +0100
committerVasily Gorbik2021-02-09 15:57:05 +0100
commiteeab78b05d202f15e58ab10675a4f736a1c9bd29 (patch)
tree579c345b9cd6c3e6d0206e50086d8f2609a9e57f /arch/s390/kernel
parent1ba2d6c0fd4e4ff5cc2372a4a5c41d65cb18f09a (diff)
s390/vdso: implement generic vdso time namespace support
Implement generic vdso time namespace support which also enables time namespaces for s390. This is quite similar to what arm64 has. Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Diffstat (limited to 'arch/s390/kernel')
-rw-r--r--arch/s390/kernel/vdso.c102
-rw-r--r--arch/s390/kernel/vdso64/vdso64.lds.S5
2 files changed, 99 insertions, 8 deletions
diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
index 31920b76ae6d..dd967af29d2b 100644
--- a/arch/s390/kernel/vdso.c
+++ b/arch/s390/kernel/vdso.c
@@ -15,12 +15,15 @@
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/smp.h>
+#include <linux/time_namespace.h>
#include <vdso/datapage.h>
#include <asm/vdso.h>
extern char vdso64_start[], vdso64_end[];
static unsigned int vdso_pages;
+static struct vm_special_mapping vvar_mapping;
+
static union {
struct vdso_data data[CS_BASES];
u8 page[PAGE_SIZE];
@@ -28,6 +31,12 @@ static union {
struct vdso_data *vdso_data = vdso_data_store.data;
+enum vvar_pages {
+ VVAR_DATA_PAGE_OFFSET,
+ VVAR_TIMENS_PAGE_OFFSET,
+ VVAR_NR_PAGES,
+};
+
unsigned int __read_mostly vdso_enabled = 1;
static int __init vdso_setup(char *str)
@@ -40,12 +49,89 @@ static int __init vdso_setup(char *str)
}
__setup("vdso=", vdso_setup);
+#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;
+ struct vm_area_struct *vma;
+
+ mmap_read_lock(mm);
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ 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)
{
- if (vmf->pgoff == 0)
- return vmf_insert_pfn(vma, vmf->address, virt_to_pfn(vdso_data));
- return VM_FAULT_SIGBUS;
+ struct page *timens_page = find_timens_vvar_page(vma);
+ unsigned long pfn;
+
+ switch (vmf->pgoff) {
+ case VVAR_DATA_PAGE_OFFSET:
+ if (timens_page)
+ pfn = page_to_pfn(timens_page);
+ else
+ pfn = virt_to_pfn(vdso_data);
+ 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,
@@ -80,23 +166,25 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
struct vm_area_struct *vma;
int rc;
+ BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
if (!vdso_enabled || is_compat_task())
return 0;
if (mmap_write_lock_killable(mm))
return -EINTR;
vdso_text_len = vdso_pages << PAGE_SHIFT;
- vdso_mapping_len = vdso_text_len + PAGE_SIZE;
+ vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
vvar_start = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
rc = vvar_start;
if (IS_ERR_VALUE(vvar_start))
goto out;
- vma = _install_special_mapping(mm, vvar_start, PAGE_SIZE,
- VM_READ|VM_MAYREAD|VM_PFNMAP,
+ 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 + PAGE_SIZE;
+ 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|
diff --git a/arch/s390/kernel/vdso64/vdso64.lds.S b/arch/s390/kernel/vdso64/vdso64.lds.S
index 99063b4c6e27..518f1ea405f4 100644
--- a/arch/s390/kernel/vdso64/vdso64.lds.S
+++ b/arch/s390/kernel/vdso64/vdso64.lds.S
@@ -13,7 +13,10 @@ ENTRY(_start)
SECTIONS
{
- PROVIDE(_vdso_data = . - PAGE_SIZE);
+ PROVIDE(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE);
+#ifdef CONFIG_TIME_NS
+ PROVIDE(_timens_data = _vdso_data + PAGE_SIZE);
+#endif
. = VDSO64_LBASE + SIZEOF_HEADERS;
.hash : { *(.hash) } :text