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    Subject[PATCH 5.14 124/151] riscv/vdso: Move vdso data page up front
    Date
    From: Tong Tiangen <tongtiangen@huawei.com>

    [ Upstream commit 78a743cd82a35ca0724179fc22834f06a2151fc2 ]

    As commit 601255ae3c98 ("arm64: vdso: move data page before code pages"), the
    same issue exists on riscv, testcase is shown below, make sure that vdso.so is
    bigger than page size,

    struct timespec tp;
    clock_gettime(5, &tp);
    printf("tv_sec: %ld, tv_nsec: %ld\n", tp.tv_sec, tp.tv_nsec);

    without this patch, test result : tv_sec: 0, tv_nsec: 0
    with this patch, test result : tv_sec: 1629271537, tv_nsec: 748000000

    Move the vdso data page in front of the VDSO area to fix the issue.

    Fixes: ad5d1122b82fb ("riscv: use vDSO common flow to reduce the latency of the time-related functions")
    Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
    Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
    Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/riscv/include/asm/vdso.h | 2 ++
    arch/riscv/kernel/vdso.c | 44 ++++++++++++++++++-------------
    arch/riscv/kernel/vdso/vdso.lds.S | 3 ++-
    3 files changed, 30 insertions(+), 19 deletions(-)

    diff --git a/arch/riscv/include/asm/vdso.h b/arch/riscv/include/asm/vdso.h
    index a4a979c89ea0..208e31bc5d1c 100644
    --- a/arch/riscv/include/asm/vdso.h
    +++ b/arch/riscv/include/asm/vdso.h
    @@ -22,6 +22,8 @@
    */
    #ifdef CONFIG_MMU

    +#define __VVAR_PAGES 1
    +
    #ifndef __ASSEMBLY__
    #include <generated/vdso-offsets.h>

    diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
    index 72e93d218335..e7bd92d8749b 100644
    --- a/arch/riscv/kernel/vdso.c
    +++ b/arch/riscv/kernel/vdso.c
    @@ -23,6 +23,13 @@ struct vdso_data {

    extern char vdso_start[], vdso_end[];

    +enum vvar_pages {
    + VVAR_DATA_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;

    @@ -41,7 +48,7 @@ static int __init vdso_init(void)

    vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
    vdso_pagelist =
    - kcalloc(vdso_pages + 1, sizeof(struct page *), GFP_KERNEL);
    + 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;
    @@ -66,7 +73,9 @@ int arch_setup_additional_pages(struct linux_binprm *bprm,
    unsigned long vdso_base, vdso_len;
    int ret;

    - vdso_len = (vdso_pages + 1) << PAGE_SHIFT;
    + BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
    +
    + vdso_len = (vdso_pages + VVAR_NR_PAGES) << PAGE_SHIFT;

    mmap_write_lock(mm);
    vdso_base = get_unmapped_area(NULL, 0, vdso_len, 0, 0);
    @@ -75,29 +84,28 @@ int arch_setup_additional_pages(struct linux_binprm *bprm,
    goto end;
    }

    - /*
    - * 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;
    + 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, vdso_pages << PAGE_SHIFT,
    + install_special_mapping(mm, vdso_base + VVAR_SIZE,
    + vdso_pages << PAGE_SHIFT,
    (VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
    vdso_pagelist);

    - if (unlikely(ret)) {
    - mm->context.vdso = NULL;
    + if (unlikely(ret))
    goto end;
    - }

    - vdso_base += (vdso_pages << PAGE_SHIFT);
    - ret = install_special_mapping(mm, vdso_base, PAGE_SIZE,
    - (VM_READ | VM_MAYREAD), &vdso_pagelist[vdso_pages]);
    + /*
    + * 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;

    - if (unlikely(ret))
    - mm->context.vdso = NULL;
    end:
    mmap_write_unlock(mm);
    return ret;
    @@ -108,7 +116,7 @@ const char *arch_vma_name(struct vm_area_struct *vma)
    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 + PAGE_SIZE))
    + (long)vma->vm_mm->context.vdso - VVAR_SIZE))
    return "[vdso_data]";
    return NULL;
    }
    diff --git a/arch/riscv/kernel/vdso/vdso.lds.S b/arch/riscv/kernel/vdso/vdso.lds.S
    index e6f558bca71b..e9111f700af0 100644
    --- a/arch/riscv/kernel/vdso/vdso.lds.S
    +++ b/arch/riscv/kernel/vdso/vdso.lds.S
    @@ -3,12 +3,13 @@
    * Copyright (C) 2012 Regents of the University of California
    */
    #include <asm/page.h>
    +#include <asm/vdso.h>

    OUTPUT_ARCH(riscv)

    SECTIONS
    {
    - PROVIDE(_vdso_data = . + PAGE_SIZE);
    + PROVIDE(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE);
    . = SIZEOF_HEADERS;

    .hash : { *(.hash) } :text
    --
    2.33.0


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