Unverified Commit 78a743cd authored by Tong Tiangen's avatar Tong Tiangen Committed by Palmer Dabbelt
Browse files

riscv/vdso: Move vdso data page up front 



As commit 601255ae ("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: ad5d1122 ("riscv: use vDSO common flow to reduce the latency of the time-related functions")
Signed-off-by: default avatarTong Tiangen <tongtiangen@huawei.com>
Reviewed-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: default avatarPalmer Dabbelt <palmerdabbelt@google.com>
parent bb4a23c9

arch/riscv/include/asm/vdso.h

+2 −0
Original line number Diff line number Diff line
@@ -22,6 +22,8 @@ 
 */

#ifdef CONFIG_MMU



#define __VVAR_PAGES    1



#ifndef __ASSEMBLY__

#include <generated/vdso-offsets.h>

arch/riscv/kernel/vdso.c

+26 −18
Original line number Diff line number Diff line
@@ -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;

}

arch/riscv/kernel/vdso/vdso.lds.S

+2 −1
Original line number Diff line number Diff line
@@ -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