[PATCH -next 1/2] riscv/vdso: Move vdso data page up front
From: Tong Tiangen
Date: Wed Aug 18 2021 - 22:58:05 EST
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.
In this patch, I moved the declaration of sys_riscv_flush_icache from asm/vdso.h
to asm/syscall.h, the reason is asm/vdso.h is included in vdso.lds.S, If the
declaration is placed here, This will introduce syntax error.
Fixes: ad5d1122b82fb ("riscv: use vDSO common flow to reduce the latency of the time-related functions")
Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
---
arch/riscv/include/asm/syscall.h | 2 ++
arch/riscv/include/asm/vdso.h | 4 +--
arch/riscv/kernel/vdso.c | 47 ++++++++++++++++++-------------
arch/riscv/kernel/vdso/vdso.lds.S | 3 +-
4 files changed, 33 insertions(+), 23 deletions(-)
diff --git a/arch/riscv/include/asm/syscall.h b/arch/riscv/include/asm/syscall.h
index b933b1583c9f..50704bd5ca3e 100644
--- a/arch/riscv/include/asm/syscall.h
+++ b/arch/riscv/include/asm/syscall.h
@@ -82,4 +82,6 @@ static inline int syscall_get_arch(struct task_struct *task)
#endif
}
+asmlinkage long sys_riscv_flush_icache(uintptr_t, uintptr_t, uintptr_t);
+
#endif /* _ASM_RISCV_SYSCALL_H */
diff --git a/arch/riscv/include/asm/vdso.h b/arch/riscv/include/asm/vdso.h
index 1453a2f563bc..564741266580 100644
--- a/arch/riscv/include/asm/vdso.h
+++ b/arch/riscv/include/asm/vdso.h
@@ -10,6 +10,8 @@
#include <linux/types.h>
+#define __VVAR_PAGES 1
+
#ifndef CONFIG_GENERIC_TIME_VSYSCALL
struct vdso_data {
};
@@ -29,6 +31,4 @@ struct vdso_data {
(void __user *)((unsigned long)(base) + __vdso_##name); \
})
-asmlinkage long sys_riscv_flush_icache(uintptr_t, uintptr_t, uintptr_t);
-
#endif /* _ASM_RISCV_VDSO_H */
diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
index 25a3b8849599..5fecd5529eff 100644
--- a/arch/riscv/kernel/vdso.c
+++ b/arch/riscv/kernel/vdso.c
@@ -14,12 +14,18 @@
#include <asm/page.h>
#ifdef CONFIG_GENERIC_TIME_VSYSCALL
#include <vdso/datapage.h>
-#else
-#include <asm/vdso.h>
#endif
+#include <asm/vdso.h>
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;
@@ -38,7 +44,7 @@ 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;
@@ -63,7 +69,9 @@ 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);
@@ -72,29 +80,28 @@ 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;
@@ -105,7 +112,7 @@ 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
--
2.18.0.huawei.25