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>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/loongarch/include/asm/page.h b/arch/loongarch/include/asm/page.h
index fb5338b352e6..26e8dccb6619 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))