[PATCH 5.14 124/151] riscv/vdso: Move vdso data page up front

Greg Kroah-Hartman
2021-10-11T14:11:10Z

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