[PATCH v3] LoongArch: Add support to clone a time namespace

Tiezhu Yang
2023-05-31T07:57:39Z

When execute the following command to test clone3 on LoongArch:

# cd tools/testing/selftests/clone3 && make && ./clone3

we can see the following error info:

# [5719] Trying clone3() with flags 0x80 (size 0)
# Invalid argument - Failed to create new process
# [5719] clone3() with flags says: -22 expected 0
not ok 18 [5719] Result (-22) is different than expected (0)

This is because if CONFIG_TIME_NS is not set, but the flag
CLONE_NEWTIME (0x80) is used to clone a time namespace, it
will return -EINVAL in copy_time_ns().

Here is the related code in include/linux/time_namespace.h:

#ifdef CONFIG_TIME_NS
...
struct time_namespace *copy_time_ns(unsigned long flags,
struct user_namespace *user_ns,
struct time_namespace *old_ns);
...
#else
...
static inline
struct time_namespace *copy_time_ns(unsigned long flags,
struct user_namespace *user_ns,
struct time_namespace *old_ns)
{
if (flags & CLONE_NEWTIME)
return ERR_PTR(-EINVAL);

return old_ns;
}
...
#endif

Here is the complete call stack:

clone3()
kernel_clone()
copy_process()
copy_namespaces()
create_new_namespaces()
copy_time_ns()
clone_time_ns()

Because CONFIG_TIME_NS depends on GENERIC_VDSO_TIME_NS, select
GENERIC_VDSO_TIME_NS to enable CONFIG_TIME_NS to build the real
implementation of copy_time_ns() in kernel/time/namespace.c.

Additionally, it needs to define some arch dependent functions
such as __arch_get_timens_vdso_data(), arch_get_vdso_data() and
vdso_join_timens(), then the above failed test can be fixed.

At the same time, modify the layout of vvar to use a page size
for generic vdso data, expand a page size for timens vdso data
and assign LOONGARCH_VDSO_DATA_SIZE (maybe over a page size if
expand in the future) for loongarch vdso data, at last add the
callback function vvar_fault().

With this patch, the following failed test can be fixed too:

# cd tools/testing/selftests/timens && make && ./timens

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---

Special thanks Wang Rui and Youling for your suggestions offline.

arch/loongarch/Kconfig | 1 +
arch/loongarch/include/asm/page.h | 1 +
arch/loongarch/include/asm/vdso/gettimeofday.h | 10 ++-
arch/loongarch/include/asm/vdso/vdso.h | 30 ++++++--
arch/loongarch/kernel/vdso.c | 98 +++++++++++++++++++++-----
arch/loongarch/vdso/vgetcpu.c | 3 +-
6 files changed, 120 insertions(+), 23 deletions(-)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index d38b066..93b167f 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -80,6 +80,7 @@ config LOONGARCH
select GENERIC_SCHED_CLOCK
select GENERIC_SMP_IDLE_THREAD
select GENERIC_TIME_VSYSCALL
+ select GENERIC_VDSO_TIME_NS
select GPIOLIB
select HAS_IOPORT
select HAVE_ARCH_AUDITSYSCALL
diff --git a/arch/loongarch/include/asm/page.h b/arch/loongarch/include/asm/page.h
index fb5338b..26e8dcc 100644
--- a/arch/loongarch/include/asm/page.h
+++ b/arch/loongarch/include/asm/page.h
@@ -81,6 +81,7 @@ typedef struct { unsigned long pgprot; } pgprot_t;
#define __va(x) ((void *)((unsigned long)(x) + PAGE_OFFSET - PHYS_OFFSET))

#define pfn_to_kaddr(pfn) __va((pfn) << PAGE_SHIFT)
+#define sym_to_pfn(x) __phys_to_pfn(__pa_symbol(x))

#define virt_to_pfn(kaddr) PFN_DOWN(PHYSADDR(kaddr))
#define virt_to_page(kaddr) pfn_to_page(virt_to_pfn(kaddr))
diff --git a/arch/loongarch/include/asm/vdso/gettimeofday.h b/arch/loongarch/include/asm/vdso/gettimeofday.h
index 7b2cd37..3c3043b 100644
--- a/arch/loongarch/include/asm/vdso/gettimeofday.h
+++ b/arch/loongarch/include/asm/vdso/gettimeofday.h
@@ -91,9 +91,17 @@ static inline bool loongarch_vdso_hres_capable(void)

static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
{
- return get_vdso_data();
+ return (const struct vdso_data *)get_vdso_data();
}

+#ifdef CONFIG_TIME_NS
+static __always_inline
+const struct vdso_data *__arch_get_timens_vdso_data(const struct vdso_data *vd)
+{
+ return (const struct vdso_data *)(get_vdso_data() +
+ VVAR_TIMENS_PAGE_OFFSET * PAGE_SIZE);
+}
+#endif
#endif /* !__ASSEMBLY__ */

#endif /* __ASM_VDSO_GETTIMEOFDAY_H */
diff --git a/arch/loongarch/include/asm/vdso/vdso.h b/arch/loongarch/include/asm/vdso/vdso.h
index 3b55d32..fa6049e 100644
--- a/arch/loongarch/include/asm/vdso/vdso.h
+++ b/arch/loongarch/include/asm/vdso/vdso.h
@@ -16,10 +16,31 @@ struct vdso_pcpu_data {

struct loongarch_vdso_data {
struct vdso_pcpu_data pdata[NR_CPUS];
- struct vdso_data data[CS_BASES]; /* Arch-independent data */
};

-#define VDSO_DATA_SIZE PAGE_ALIGN(sizeof(struct loongarch_vdso_data))
+/*
+ * The layout of vvar:
+ *
+ * high
+ * +---------------------+--------------------------+
+ * | loongarch vdso data | LOONGARCH_VDSO_DATA_SIZE |
+ * +---------------------+--------------------------+
+ * | timens vdso data | PAGE_SIZE |
+ * +---------------------+--------------------------+
+ * | generic vdso data | PAGE_SIZE |
+ * +---------------------+--------------------------+
+ * low
+ */
+#define LOONGARCH_VDSO_DATA_SIZE PAGE_ALIGN(sizeof(struct loongarch_vdso_data))
+#define LOONGARCH_VDSO_DATA_PAGES (LOONGARCH_VDSO_DATA_SIZE >> PAGE_SHIFT)
+#define VVAR_SIZE (VVAR_LOONGARCH_PAGES_START * PAGE_SIZE + LOONGARCH_VDSO_DATA_SIZE)
+
+enum vvar_pages {
+ VVAR_GENERIC_PAGE_OFFSET,
+ VVAR_TIMENS_PAGE_OFFSET,
+ VVAR_LOONGARCH_PAGES_START,
+ VVAR_LOONGARCH_PAGES_END = VVAR_LOONGARCH_PAGES_START + LOONGARCH_VDSO_DATA_PAGES - 1,
+};

static inline unsigned long get_vdso_base(void)
{
@@ -34,10 +55,9 @@ static inline unsigned long get_vdso_base(void)
return addr;
}

-static inline const struct vdso_data *get_vdso_data(void)
+static inline unsigned long get_vdso_data(void)
{
- return (const struct vdso_data *)(get_vdso_base()
- - VDSO_DATA_SIZE + SMP_CACHE_BYTES * NR_CPUS);
+ return get_vdso_base() - VVAR_SIZE;
}

#endif /* __ASSEMBLY__ */
diff --git a/arch/loongarch/kernel/vdso.c b/arch/loongarch/kernel/vdso.c
index eaebd2e..cb75863 100644
--- a/arch/loongarch/kernel/vdso.c
+++ b/arch/loongarch/kernel/vdso.c
@@ -14,6 +14,7 @@
#include <linux/random.h>
#include <linux/sched.h>
#include <linux/slab.h>
+#include <linux/time_namespace.h>
#include <linux/timekeeper_internal.h>

#include <asm/page.h>
@@ -26,12 +27,17 @@ extern char vdso_start[], vdso_end[];

/* Kernel-provided data used by the VDSO. */
static union {
- u8 page[VDSO_DATA_SIZE];
+ u8 page[PAGE_SIZE];
+ struct vdso_data data[CS_BASES];
+} generic_vdso_data __page_aligned_data;
+
+static union {
+ u8 page[LOONGARCH_VDSO_DATA_SIZE];
struct loongarch_vdso_data vdata;
} loongarch_vdso_data __page_aligned_data;

static struct page *vdso_pages[] = { NULL };
-struct vdso_data *vdso_data = loongarch_vdso_data.vdata.data;
+struct vdso_data *vdso_data = generic_vdso_data.data;
struct vdso_pcpu_data *vdso_pdata = loongarch_vdso_data.vdata.pdata;

static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
@@ -41,6 +47,43 @@ static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struc
return 0;
}

+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 pfn;
+
+ switch (vmf->pgoff) {
+ case VVAR_GENERIC_PAGE_OFFSET:
+ if (timens_page)
+ pfn = page_to_pfn(timens_page);
+ else
+ pfn = sym_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_GENERIC_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 = sym_to_pfn(vdso_data);
+ break;
+#endif /* CONFIG_TIME_NS */
+ case VVAR_LOONGARCH_PAGES_START ... VVAR_LOONGARCH_PAGES_END:
+ pfn = sym_to_pfn(&loongarch_vdso_data) +
+ vmf->pgoff - VVAR_LOONGARCH_PAGES_START;
+ break;
+ default:
+ return VM_FAULT_SIGBUS;
+ }
+
+ return vmf_insert_pfn(vma, vmf->address, pfn);
+}
+
struct loongarch_vdso_info vdso_info = {
.vdso = vdso_start,
.size = PAGE_SIZE,
@@ -51,6 +94,7 @@ struct loongarch_vdso_info vdso_info = {
},
.data_mapping = {
.name = "[vvar]",
+ .fault = vvar_fault,
},
.offset_sigreturn = vdso_offset_sigreturn,
};
@@ -73,6 +117,37 @@ static int __init init_vdso(void)
}
subsys_initcall(init_vdso);

+#ifdef CONFIG_TIME_NS
+struct vdso_data *arch_get_vdso_data(void *vvar_page)
+{
+ return (struct vdso_data *)(vvar_page);
+}
+
+/*
+ * The vvar mapping contains data for a specific time namespace, so when a
+ * task changes namespace we must unmap its vvar data for the old namespace.
+ * Subsequent faults will map in data for the new namespace.
+ *
+ * For more details see timens_setup_vdso_data().
+ */
+int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
+{
+ struct mm_struct *mm = task->mm;
+ struct vm_area_struct *vma;
+
+ VMA_ITERATOR(vmi, mm, 0);
+
+ mmap_read_lock(mm);
+ for_each_vma(vmi, vma) {
+ if (vma_is_special_mapping(vma, &vdso_info.data_mapping))
+ zap_vma_pages(vma);
+ }
+ mmap_read_unlock(mm);
+
+ return 0;
+}
+#endif
+
static unsigned long vdso_base(void)
{
unsigned long base = STACK_TOP;
@@ -88,7 +163,7 @@ static unsigned long vdso_base(void)
int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
int ret;
- unsigned long vvar_size, size, data_addr, vdso_addr;
+ unsigned long size, data_addr, vdso_addr;
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
struct loongarch_vdso_info *info = current->thread.vdso;
@@ -100,32 +175,23 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
* Determine total area size. This includes the VDSO data itself
* and the data pages.
*/
- vvar_size = VDSO_DATA_SIZE;
- size = vvar_size + info->size;
+ size = VVAR_SIZE + info->size;

data_addr = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
if (IS_ERR_VALUE(data_addr)) {
ret = data_addr;
goto out;
}
- vdso_addr = data_addr + VDSO_DATA_SIZE;

- vma = _install_special_mapping(mm, data_addr, vvar_size,
- VM_READ | VM_MAYREAD,
+ vma = _install_special_mapping(mm, data_addr, VVAR_SIZE,
+ VM_READ | VM_MAYREAD | VM_PFNMAP,
&info->data_mapping);
if (IS_ERR(vma)) {
ret = PTR_ERR(vma);
goto out;
}

- /* Map VDSO data page. */
- ret = remap_pfn_range(vma, data_addr,
- virt_to_phys(&loongarch_vdso_data) >> PAGE_SHIFT,
- vvar_size, PAGE_READONLY);
- if (ret)
- goto out;
-
- /* Map VDSO code page. */
+ vdso_addr = data_addr + VVAR_SIZE;
vma = _install_special_mapping(mm, vdso_addr, info->size,
VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
&info->code_mapping);
diff --git a/arch/loongarch/vdso/vgetcpu.c b/arch/loongarch/vdso/vgetcpu.c
index e02e775..e7884f88 100644
--- a/arch/loongarch/vdso/vgetcpu.c
+++ b/arch/loongarch/vdso/vgetcpu.c
@@ -21,7 +21,8 @@ static __always_inline int read_cpu_id(void)

static __always_inline const struct vdso_pcpu_data *get_pcpu_data(void)
{
- return (struct vdso_pcpu_data *)(get_vdso_base() - VDSO_DATA_SIZE);
+ return (struct vdso_pcpu_data *)(get_vdso_data() +
+ VVAR_LOONGARCH_PAGES_START * PAGE_SIZE);
}

extern
--
2.1.0