[PATCH v3 11/18] arm: vdso: Switch to generic storage implementation

Thomas Weißschuh
2025-02-04T12:06:14Z

The generic storage implementation provides the same features as the
custom one. However it can be shared between architectures, making
maintenance easier.

Co-developed-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
arch/arm/include/asm/vdso.h | 2 ++
arch/arm/include/asm/vdso/gettimeofday.h | 7 +------
arch/arm/include/asm/vdso/vsyscall.h | 12 ++---------
arch/arm/kernel/asm-offsets.c | 4 ----
arch/arm/kernel/vdso.c | 34 +++++++-------------------------
arch/arm/mm/Kconfig | 1 +
arch/arm/vdso/vdso.lds.S | 4 ++--
7 files changed, 15 insertions(+), 49 deletions(-)

diff --git a/arch/arm/include/asm/vdso.h b/arch/arm/include/asm/vdso.h
index 5b85889f82eeb422400c039e8b5e8a2a6d4553b3..88364a6727ffce224edd35dd62db1693ae5fcb1c 100644
--- a/arch/arm/include/asm/vdso.h
+++ b/arch/arm/include/asm/vdso.h
@@ -4,6 +4,8 @@

#ifdef __KERNEL__

+#define __VDSO_PAGES 4
+
#ifndef __ASSEMBLY__

struct mm_struct;
diff --git a/arch/arm/include/asm/vdso/gettimeofday.h b/arch/arm/include/asm/vdso/gettimeofday.h
index 592d3d015ca7298b3bc35871387dbb3e7f819827..1e9f81639c88cc23cae7cf267bf4674c6d6acec0 100644
--- a/arch/arm/include/asm/vdso/gettimeofday.h
+++ b/arch/arm/include/asm/vdso/gettimeofday.h
@@ -112,7 +112,7 @@ static inline bool arm_vdso_hres_capable(void)
#define __arch_vdso_hres_capable arm_vdso_hres_capable

static __always_inline u64 __arch_get_hw_counter(int clock_mode,
- const struct vdso_data *vd)
+ const struct vdso_time_data *vd)
{
#ifdef CONFIG_ARM_ARCH_TIMER
u64 cycle_now;
@@ -135,11 +135,6 @@ static __always_inline u64 __arch_get_hw_counter(int clock_mode,
#endif
}

-static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
-{
- return _vdso_data;
-}
-
#endif /* !__ASSEMBLY__ */

#endif /* __ASM_VDSO_GETTIMEOFDAY_H */
diff --git a/arch/arm/include/asm/vdso/vsyscall.h b/arch/arm/include/asm/vdso/vsyscall.h
index 705414710dcdbfa9a97c344806bd079c08368801..4e7226ad02ec4dcf88203c9046e1b320a10e7373 100644
--- a/arch/arm/include/asm/vdso/vsyscall.h
+++ b/arch/arm/include/asm/vdso/vsyscall.h
@@ -7,22 +7,14 @@
#include <vdso/datapage.h>
#include <asm/cacheflush.h>

-extern struct vdso_data *vdso_data;
extern bool cntvct_ok;

static __always_inline
-struct vdso_data *__arm_get_k_vdso_data(void)
-{
- return vdso_data;
-}
-#define __arch_get_k_vdso_data __arm_get_k_vdso_data
-
-static __always_inline
-void __arm_sync_vdso_data(struct vdso_data *vdata)
+void __arch_sync_vdso_time_data(struct vdso_time_data *vdata)
{
flush_dcache_page(virt_to_page(vdata));
}
-#define __arch_sync_vdso_data __arm_sync_vdso_data
+#define __arch_sync_vdso_time_data __arch_sync_vdso_time_data

/* The asm-generic header needs to be included after the definitions above */
#include <asm-generic/vdso/vsyscall.h>
diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
index 4853875740d0fe61c6bbc32ddd9a16fa8d1fb530..123f4a8ef44660a39c4eff2a6e5fd86cb48fb572 100644
--- a/arch/arm/kernel/asm-offsets.c
+++ b/arch/arm/kernel/asm-offsets.c
@@ -153,10 +153,6 @@ int main(void)
DEFINE(CACHE_WRITEBACK_ORDER, __CACHE_WRITEBACK_ORDER);
DEFINE(CACHE_WRITEBACK_GRANULE, __CACHE_WRITEBACK_GRANULE);
BLANK();
-#ifdef CONFIG_VDSO
- DEFINE(VDSO_DATA_SIZE, sizeof(union vdso_data_store));
-#endif
- BLANK();
#ifdef CONFIG_ARM_MPU
DEFINE(MPU_RNG_INFO_RNGS, offsetof(struct mpu_rgn_info, rgns));
DEFINE(MPU_RNG_INFO_USED, offsetof(struct mpu_rgn_info, used));
diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
index 29dd2f3c62fec64c7f290468421bfad1e739c667..325448ffbba0c29895ea5d97e60d6f51e552cb2e 100644
--- a/arch/arm/kernel/vdso.c
+++ b/arch/arm/kernel/vdso.c
@@ -7,6 +7,7 @@
*/

#include <linux/cache.h>
+#include <linux/vdso_datastore.h>
#include <linux/elf.h>
#include <linux/err.h>
#include <linux/kernel.h>
@@ -33,15 +34,6 @@ extern char vdso_start[], vdso_end[];
/* Total number of pages needed for the data and text portions of the VDSO. */
unsigned int vdso_total_pages __ro_after_init;

-static union vdso_data_store vdso_data_store __page_aligned_data;
-struct vdso_data *vdso_data = vdso_data_store.data;
-
-static struct page *vdso_data_page __ro_after_init;
-static const struct vm_special_mapping vdso_data_mapping = {
- .name = "[vvar]",
- .pages = &vdso_data_page,
-};
-
static int vdso_mremap(const struct vm_special_mapping *sm,
struct vm_area_struct *new_vma)
{
@@ -192,9 +184,6 @@ static int __init vdso_init(void)
if (vdso_text_pagelist == NULL)
return -ENOMEM;

- /* Grab the VDSO data page. */
- vdso_data_page = virt_to_page(vdso_data);
-
/* Grab the VDSO text pages. */
for (i = 0; i < text_pages; i++) {
struct page *page;
@@ -205,7 +194,7 @@ static int __init vdso_init(void)

vdso_text_mapping.pages = vdso_text_pagelist;

- vdso_total_pages = 1; /* for the data/vvar page */
+ vdso_total_pages = VDSO_NR_PAGES; /* for the data/vvar pages */
vdso_total_pages += text_pages;

cntvct_ok = cntvct_functional();
@@ -216,16 +205,7 @@ static int __init vdso_init(void)
}
arch_initcall(vdso_init);

-static int install_vvar(struct mm_struct *mm, unsigned long addr)
-{
- struct vm_area_struct *vma;
-
- vma = _install_special_mapping(mm, addr, PAGE_SIZE,
- VM_READ | VM_MAYREAD,
- &vdso_data_mapping);
-
- return PTR_ERR_OR_ZERO(vma);
-}
+static_assert(__VDSO_PAGES == VDSO_NR_PAGES);

/* assumes mmap_lock is write-locked */
void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
@@ -238,12 +218,12 @@ void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
if (vdso_text_pagelist == NULL)
return;

- if (install_vvar(mm, addr))
+ if (IS_ERR(vdso_install_vvar_mapping(mm, addr)))
return;

- /* Account for vvar page. */
- addr += PAGE_SIZE;
- len = (vdso_total_pages - 1) << PAGE_SHIFT;
+ /* Account for vvar pages. */
+ addr += VDSO_NR_PAGES * PAGE_SIZE;
+ len = (vdso_total_pages - VDSO_NR_PAGES) << PAGE_SHIFT;

vma = _install_special_mapping(mm, addr, len,
VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 2b6f50dd547840adecbe08e684ed8f1a032cd7c2..5c1023a6d78c1b4db67b2d62b71af5a79b7e701f 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -928,6 +928,7 @@ config VDSO
select GENERIC_TIME_VSYSCALL
select GENERIC_VDSO_32
select GENERIC_GETTIMEOFDAY
+ select GENERIC_VDSO_DATA_STORE
help
Place in the process address space an ELF shared object
providing fast implementations of gettimeofday and
diff --git a/arch/arm/vdso/vdso.lds.S b/arch/arm/vdso/vdso.lds.S
index 9bfa0f52923c851b6b9e96d4dbb51eb3d5d0960a..7c08371f440027f9a52e9fffae530d7db05b7c43 100644
--- a/arch/arm/vdso/vdso.lds.S
+++ b/arch/arm/vdso/vdso.lds.S
@@ -11,16 +11,16 @@
*/

#include <linux/const.h>
-#include <asm/asm-offsets.h>
#include <asm/page.h>
#include <asm/vdso.h>
+#include <vdso/datapage.h>

OUTPUT_FORMAT("elf32-littlearm", "elf32-bigarm", "elf32-littlearm")
OUTPUT_ARCH(arm)

SECTIONS
{
- PROVIDE(_vdso_data = . - VDSO_DATA_SIZE);
+ VDSO_VVAR_SYMS

. = SIZEOF_HEADERS;

--
2.48.1