LoongArch: Add support to clone a time namespace

We can see that "Time namespaces are not supported" on LoongArch:

(1) clone3 test
  # cd tools/testing/selftests/clone3 && make && ./clone3
  ...
  # Time namespaces are not supported
  ok 18 # SKIP Skipping clone3() with CLONE_NEWTIME
  # Totals: pass:17 fail:0 xfail:0 xpass:0 skip:1 error:0

(2) timens test
  # cd tools/testing/selftests/timens && make && ./timens
  ...
  1..0 # SKIP Time namespaces are not supported

On LoongArch the current kernel does not support CONFIG_TIME_NS which
depends on GENERIC_VDSO_TIME_NS, select GENERIC_VDSO_TIME_NS to enable
CONFIG_TIME_NS to build kernel/time/namespace.c.

Additionally, it needs to define some arch-dependent functions for the
timens, such as __arch_get_timens_vdso_data(), arch_get_vdso_data() and
vdso_join_timens().

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

With this patch under CONFIG_TIME_NS:

(1) clone3 test
  # cd tools/testing/selftests/clone3 && make && ./clone3
  ...
  ok 18 [739] Result (0) matches expectation (0)
  # Totals: pass:18 fail:0 xfail:0 xpass:0 skip:0 error:0

(2) timens test
  # cd tools/testing/selftests/timens && make && ./timens
  ...
  # Totals: pass:10 fail:0 xfail:0 xpass:0 skip:0 error:0

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

2 files changed, 35 insertions, 6 deletions

diff --git a/arch/loongarch/include/asm/vdso/gettimeofday.h b/arch/loongarch/include/asm/vdso/gettimeofday.h
index 7b2cd37641e2..89e6b222c2f2 100644
--- a/arch/loongarch/include/asm/vdso/gettimeofday.h
+++ b/arch/loongarch/include/asm/vdso/gettimeofday.h
@@ -91,9 +91,16 @@ 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 3b55d32a0619..5a12309d9fb5 100644
--- a/arch/loongarch/include/asm/vdso/vdso.h
+++ b/arch/loongarch/include/asm/vdso/vdso.h
@@ -16,10 +16,33 @@ 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 |
+ * +---------------------+--------------------------+
+ * |  time-ns 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)
+
+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,
+	VVAR_NR_PAGES,
+};
+
+#define VVAR_SIZE (VVAR_NR_PAGES << PAGE_SHIFT)
 
 static inline unsigned long get_vdso_base(void)
 {
@@ -34,10 +57,9 @@ 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__ */