[PATCH -next] riscv/vdso: Add support for time namespaces

From: Tong Tiangen
Date: Tue Aug 31 2021 - 23:11:40 EST

Implement generic vdso time namespace support which also enables time
namespaces for riscv. This is quite similar to what arm64 does.

selftest/timens test result:
1..10
ok 1 Passed for CLOCK_BOOTTIME (syscall)
ok 2 Passed for CLOCK_BOOTTIME (vdso)
ok 3 # SKIP CLOCK_BOOTTIME_ALARM isn't supported
ok 4 # SKIP CLOCK_BOOTTIME_ALARM isn't supported
ok 5 Passed for CLOCK_MONOTONIC (syscall)
ok 6 Passed for CLOCK_MONOTONIC (vdso)
ok 7 Passed for CLOCK_MONOTONIC_COARSE (syscall)
ok 8 Passed for CLOCK_MONOTONIC_COARSE (vdso)
ok 9 Passed for CLOCK_MONOTONIC_RAW (syscall)
ok 10 Passed for CLOCK_MONOTONIC_RAW (vdso)
# Totals: pass:8 fail:0 xfail:0 xpass:0 skip:2 error:0

Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
---
This patch is based on patchset:
https://lore.kernel.org/lkml/20210901024621.2528797-1-tongtiangen@xxxxxxxxxx/

arch/riscv/Kconfig | 1 +
arch/riscv/include/asm/page.h | 2 +
arch/riscv/include/asm/vdso.h | 2 +-
arch/riscv/include/asm/vdso/gettimeofday.h | 7 +
arch/riscv/kernel/vdso.c | 250 ++++++++++++++++-----
arch/riscv/kernel/vdso/vdso.lds.S | 3 +
6 files changed, 211 insertions(+), 54 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index aac669a6c3d8..7b0eff8a7eef 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -61,6 +61,7 @@ config RISCV
select GENERIC_SCHED_CLOCK
select GENERIC_SMP_IDLE_THREAD
select GENERIC_TIME_VSYSCALL if MMU && 64BIT
+ select GENERIC_VDSO_TIME_NS if HAVE_GENERIC_VDSO
select HANDLE_DOMAIN_IRQ
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL
diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
index 109c97e991a6..b3e5ff0125fe 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -157,6 +157,8 @@ extern phys_addr_t __phys_addr_symbol(unsigned long x);
#define page_to_bus(page) (page_to_phys(page))
#define phys_to_page(paddr) (pfn_to_page(phys_to_pfn(paddr)))

+#define sym_to_pfn(x) __phys_to_pfn(__pa_symbol(x))
+
#ifdef CONFIG_FLATMEM
#define pfn_valid(pfn) \
(((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET) < max_mapnr))
diff --git a/arch/riscv/include/asm/vdso.h b/arch/riscv/include/asm/vdso.h
index 34210b22ba91..bee9514104f7 100644
--- a/arch/riscv/include/asm/vdso.h
+++ b/arch/riscv/include/asm/vdso.h
@@ -14,7 +14,7 @@
*/
#ifdef CONFIG_MMU

-#define __VVAR_PAGES 1
+#define __VVAR_PAGES 2

#ifndef __ASSEMBLY__

diff --git a/arch/riscv/include/asm/vdso/gettimeofday.h b/arch/riscv/include/asm/vdso/gettimeofday.h
index f839f16e0d2a..77d9c2f721c4 100644
--- a/arch/riscv/include/asm/vdso/gettimeofday.h
+++ b/arch/riscv/include/asm/vdso/gettimeofday.h
@@ -76,6 +76,13 @@ static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
return _vdso_data;
}

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

#endif /* __ASM_VDSO_GETTIMEOFDAY_H */
diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
index b70956d80408..a9436a65161a 100644
--- a/arch/riscv/kernel/vdso.c
+++ b/arch/riscv/kernel/vdso.c
@@ -13,6 +13,7 @@
#include <linux/err.h>
#include <asm/page.h>
#include <asm/vdso.h>
+#include <linux/time_namespace.h>

#ifdef CONFIG_GENERIC_TIME_VSYSCALL
#include <vdso/datapage.h>
@@ -25,14 +26,12 @@ extern char vdso_start[], vdso_end[];

enum vvar_pages {
VVAR_DATA_PAGE_OFFSET,
+ VVAR_TIMENS_PAGE_OFFSET,
VVAR_NR_PAGES,
};

#define VVAR_SIZE (VVAR_NR_PAGES << PAGE_SHIFT)

-static unsigned int vdso_pages __ro_after_init;
-static struct page **vdso_pagelist __ro_after_init;
-
/*
* The vDSO data page.
*/
@@ -42,83 +41,228 @@ static union {
} vdso_data_store __page_aligned_data;
struct vdso_data *vdso_data = &vdso_data_store.data;

-static int __init vdso_init(void)
+struct __vdso_info {
+ const char *name;
+ const char *vdso_code_start;
+ const char *vdso_code_end;
+ unsigned long vdso_pages;
+ /* Data Mapping */
+ struct vm_special_mapping *dm;
+ /* Code Mapping */
+ struct vm_special_mapping *cm;
+};
+
+static struct __vdso_info vdso_info __ro_after_init = {
+ .name = "vdso",
+ .vdso_code_start = vdso_start,
+ .vdso_code_end = vdso_end,
+};
+
+static int vdso_mremap(const struct vm_special_mapping *sm,
+ struct vm_area_struct *new_vma)
+{
+ current->mm->context.vdso = (void *)new_vma->vm_start;
+
+ return 0;
+}
+
+static int __init __vdso_init(void)
{
unsigned int i;
+ struct page **vdso_pagelist;
+ unsigned long pfn;

- vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
- vdso_pagelist =
- kcalloc(vdso_pages + VVAR_NR_PAGES, sizeof(struct page *), GFP_KERNEL);
- if (unlikely(vdso_pagelist == NULL)) {
- pr_err("vdso: pagelist allocation failed\n");
- return -ENOMEM;
+ if (memcmp(vdso_info.vdso_code_start, "\177ELF", 4)) {
+ pr_err("vDSO is not a valid ELF object!\n");
+ return -EINVAL;
}

- for (i = 0; i < vdso_pages; i++) {
- struct page *pg;
+ vdso_info.vdso_pages = (
+ vdso_info.vdso_code_end -
+ vdso_info.vdso_code_start) >>
+ PAGE_SHIFT;
+
+ vdso_pagelist = kcalloc(vdso_info.vdso_pages,
+ sizeof(struct page *),
+ GFP_KERNEL);
+ if (vdso_pagelist == NULL)
+ return -ENOMEM;
+
+ /* Grab the vDSO code pages. */
+ pfn = sym_to_pfn(vdso_info.vdso_code_start);
+
+ for (i = 0; i < vdso_info.vdso_pages; i++)
+ vdso_pagelist[i] = pfn_to_page(pfn + i);
+
+ vdso_info.cm->pages = vdso_pagelist;
+
+ return 0;
+}
+
+#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;
+
+ mmap_read_lock(mm);

- pg = virt_to_page(vdso_start + (i << PAGE_SHIFT));
- vdso_pagelist[i] = pg;
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ unsigned long size = vma->vm_end - vma->vm_start;
+
+ if (vma_is_special_mapping(vma, vdso_info.dm))
+ zap_page_range(vma, vma->vm_start, size);
}
- vdso_pagelist[i] = virt_to_page(vdso_data);

+ mmap_read_unlock(mm);
return 0;
}
+
+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;
+}
+#else
+static 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)
+{
+ 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 = 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_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 = sym_to_pfn(vdso_data);
+ break;
+#endif /* CONFIG_TIME_NS */
+ default:
+ return VM_FAULT_SIGBUS;
+ }
+
+ return vmf_insert_pfn(vma, vmf->address, pfn);
+}
+
+enum rv_vdso_map {
+ RV_VDSO_MAP_VVAR,
+ RV_VDSO_MAP_VDSO,
+};
+
+static struct vm_special_mapping rv_vdso_maps[] __ro_after_init = {
+ [RV_VDSO_MAP_VVAR] = {
+ .name = "[vvar]",
+ .fault = vvar_fault,
+ },
+ [RV_VDSO_MAP_VDSO] = {
+ .name = "[vdso]",
+ .mremap = vdso_mremap,
+ },
+};
+
+static int __init vdso_init(void)
+{
+ vdso_info.dm = &rv_vdso_maps[RV_VDSO_MAP_VVAR];
+ vdso_info.cm = &rv_vdso_maps[RV_VDSO_MAP_VDSO];
+
+ return __vdso_init();
+}
arch_initcall(vdso_init);

-int arch_setup_additional_pages(struct linux_binprm *bprm,
- int uses_interp)
+static int __setup_additional_pages(struct mm_struct *mm,
+ struct linux_binprm *bprm,
+ int uses_interp)
{
- struct mm_struct *mm = current->mm;
- unsigned long vdso_base, vdso_len;
- int ret;
+ unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
+ void *ret;

BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);

- vdso_len = (vdso_pages + VVAR_NR_PAGES) << PAGE_SHIFT;
+ vdso_text_len = vdso_info.vdso_pages << PAGE_SHIFT;
+ /* Be sure to map the data page */
+ vdso_mapping_len = vdso_text_len + VVAR_SIZE;

- if (mmap_write_lock_killable(mm))
- return -EINTR;
-
- vdso_base = get_unmapped_area(NULL, 0, vdso_len, 0, 0);
+ vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
if (IS_ERR_VALUE(vdso_base)) {
- ret = vdso_base;
- goto end;
+ ret = ERR_PTR(vdso_base);
+ goto up_fail;
}

- mm->context.vdso = NULL;
- ret = install_special_mapping(mm, vdso_base, VVAR_SIZE,
- (VM_READ | VM_MAYREAD), &vdso_pagelist[vdso_pages]);
- if (unlikely(ret))
- goto end;
+ ret = _install_special_mapping(mm, vdso_base, VVAR_SIZE,
+ (VM_READ | VM_MAYREAD | VM_PFNMAP), vdso_info.dm);
+ if (IS_ERR(ret))
+ goto up_fail;

+ vdso_base += VVAR_SIZE;
+ mm->context.vdso = (void *)vdso_base;
ret =
- install_special_mapping(mm, vdso_base + VVAR_SIZE,
- vdso_pages << PAGE_SHIFT,
+ _install_special_mapping(mm, vdso_base, vdso_text_len,
(VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
- vdso_pagelist);
+ vdso_info.cm);

- if (unlikely(ret))
- goto end;
+ if (IS_ERR(ret))
+ goto up_fail;

- /*
- * Put vDSO base into mm struct. We need to do this before calling
- * install_special_mapping or the perf counter mmap tracking code
- * will fail to recognise it as a vDSO (since arch_vma_name fails).
- */
- mm->context.vdso = (void *)vdso_base + VVAR_SIZE;
+ return 0;

-end:
- mmap_write_unlock(mm);
- return ret;
+up_fail:
+ mm->context.vdso = NULL;
+ return PTR_ERR(ret);
}

-const char *arch_vma_name(struct vm_area_struct *vma)
+int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
- if (vma->vm_mm && (vma->vm_start == (long)vma->vm_mm->context.vdso))
- return "[vdso]";
- if (vma->vm_mm && (vma->vm_start ==
- (long)vma->vm_mm->context.vdso - VVAR_SIZE))
- return "[vdso_data]";
- return NULL;
+ struct mm_struct *mm = current->mm;
+ int ret;
+
+ if (mmap_write_lock_killable(mm))
+ return -EINTR;
+
+ ret = __setup_additional_pages(mm, bprm, uses_interp);
+ mmap_write_unlock(mm);
+
+ return ret;
}
diff --git a/arch/riscv/kernel/vdso/vdso.lds.S b/arch/riscv/kernel/vdso/vdso.lds.S
index e9111f700af0..01d94aae5bf5 100644
--- a/arch/riscv/kernel/vdso/vdso.lds.S
+++ b/arch/riscv/kernel/vdso/vdso.lds.S
@@ -10,6 +10,9 @@ OUTPUT_ARCH(riscv)
SECTIONS
{
PROVIDE(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE);
+#ifdef CONFIG_TIME_NS
+ PROVIDE(_timens_data = _vdso_data + PAGE_SIZE);
+#endif
. = SIZEOF_HEADERS;

.hash : { *(.hash) } :text
--
2.18.0.huawei.25