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Message-ID: <CAAhV-H76kp+hoNUpN7znf9K6bmawShNkCVu2r=mFtAcq2xcVnQ@mail.gmail.com>
Date: Wed, 7 Jun 2023 17:18:35 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc: Christian Brauner <brauner@...nel.org>,
Andy Lutomirski <luto@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Vincenzo Frascino <vincenzo.frascino@....com>,
loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH v4 2/2] LoongArch: Add support to clone a time namespace
Queued for loongarch-next, thanks.
Huacai
On Mon, Jun 5, 2023 at 8:33 PM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>
> 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
>
> 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
> 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 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() 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@...ngson.cn>
> ---
> 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 | 32 +++++++--
> arch/loongarch/kernel/process.c | 2 +-
> arch/loongarch/kernel/vdso.c | 98 +++++++++++++++++++++-----
> arch/loongarch/vdso/vgetcpu.c | 3 +-
> 7 files changed, 123 insertions(+), 24 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..7e9bceb 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 |
> + * +---------------------+--------------------------+
> + * | 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)
> +
> +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__ */
> diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
> index b71e17c..9535a06 100644
> --- a/arch/loongarch/kernel/process.c
> +++ b/arch/loongarch/kernel/process.c
> @@ -285,7 +285,7 @@ unsigned long stack_top(void)
>
> /* Space for the VDSO & data page */
> top -= PAGE_ALIGN(current->thread.vdso->size);
> - top -= PAGE_SIZE;
> + top -= VVAR_SIZE;
>
> /* Space to randomize the VDSO base */
> if (current->flags & PF_RANDOMIZE)
> 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
>
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