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riscv/vdso: Move vdso data page up front

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As commit 601255ae3c ("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: ad5d1122b8 ("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>
This commit is contained in:
Tong Tiangen 2021-09-01 02:46:20 +00:00 committed by Palmer Dabbelt
parent bb4a23c994
commit 78a743cd82
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
3 changed files with 32 additions and 21 deletions
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2
arch/riscv/include/asm/vdso.h
View File

@ -22,6 +22,8 @@
*/
#ifdef CONFIG_MMU
#define __VVAR_PAGES 1
#ifndef __ASSEMBLY__
#include <generated/vdso-offsets.h>

48
arch/riscv/kernel/vdso.c
View File

@ -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;
}
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,
vdso_pages << PAGE_SHIFT,
(VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
vdso_pagelist);
if (unlikely(ret))
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 = (void *)vdso_base + VVAR_SIZE;
ret =
install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
(VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
vdso_pagelist);
if (unlikely(ret)) {
mm->context.vdso = NULL;
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]);
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;
}

3
arch/riscv/kernel/vdso/vdso.lds.S
View File

@ -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