linux-kernel - [PATCH] LoongArch: Add support to clone a time namespace

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Date:   Wed, 17 May 2023 11:03:00 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Christian Brauner <brauner@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vincenzo Frascino <vincenzo.frascino@....com>
Cc:     loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
        loongson-kernel@...ts.loongnix.cn
Subject: [PATCH] LoongArch: Add support to clone a time namespace

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 failed test can be fixed.

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

This is based on 6.4-rc2

 arch/loongarch/Kconfig                         |  1 +
 arch/loongarch/include/asm/vdso/gettimeofday.h |  7 ++++++
 arch/loongarch/kernel/vdso.c                   | 32 ++++++++++++++++++++++++++
 3 files changed, 40 insertions(+)

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/vdso/gettimeofday.h b/arch/loongarch/include/asm/vdso/gettimeofday.h
index 7b2cd37..1af88ac 100644
--- a/arch/loongarch/include/asm/vdso/gettimeofday.h
+++ b/arch/loongarch/include/asm/vdso/gettimeofday.h
@@ -94,6 +94,13 @@ static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
 	return 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 get_vdso_data() + PAGE_SIZE;
+}
+#endif
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_VDSO_GETTIMEOFDAY_H */
diff --git a/arch/loongarch/kernel/vdso.c b/arch/loongarch/kernel/vdso.c
index eaebd2e..cf62103 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>
@@ -73,6 +74,37 @@ 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;
-- 
2.1.0