vdso: Add generic architecture-specific data storage

Some architectures need to expose architecture-specific data to the vDSO.

Enable the generic vDSO storage mechanism to both store and map this
data. Some architectures require more than a single page, like LoongArch,
so prepare for that usecase, too.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250204-vdso-store-rng-v3-7-13a4669dfc8c@linutronix.de

diff --git a/arch/Kconfig b/arch/Kconfig
index b8a4ff36558228240080a5677f702d37f4f8d547..9f6eb09ef12d76e755c0fd2df71ba703c251052f 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1584,6 +1584,10 @@ config HAVE_SPARSE_SYSCALL_NR
          entries at 4000, 5000 and 6000 locations. This option turns on syscall
          related optimizations for a given architecture.
 
+config ARCH_HAS_VDSO_ARCH_DATA
+       depends on GENERIC_VDSO_DATA_STORE
+       bool
+
 config ARCH_HAS_VDSO_TIME_DATA
        bool
 

diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
index 7dbc8797e3b8923c06f4b6b34790766e68b2abd2..46658b39c28250e977f5a3454224c3ed0fb4c81d 100644 (file)
--- a/include/vdso/datapage.h
+++ b/include/vdso/datapage.h
@@ -9,11 +9,13 @@
 #include <uapi/linux/types.h>
 #include <uapi/asm-generic/errno-base.h>
 
+#include <vdso/align.h>
 #include <vdso/bits.h>
 #include <vdso/clocksource.h>
 #include <vdso/ktime.h>
 #include <vdso/limits.h>
 #include <vdso/math64.h>
+#include <vdso/page.h>
 #include <vdso/processor.h>
 #include <vdso/time.h>
 #include <vdso/time32.h>
@@ -25,6 +27,15 @@
 struct arch_vdso_time_data {};
 #endif
 
+#if defined(CONFIG_ARCH_HAS_VDSO_ARCH_DATA)
+#include <asm/vdso/arch_data.h>
+#elif defined(CONFIG_GENERIC_VDSO_DATA_STORE)
+struct vdso_arch_data {
+       /* Needed for the generic code, never actually used at runtime */
+       char __unused;
+};
+#endif
+
 #define VDSO_BASES     (CLOCK_TAI + 1)
 #define VDSO_HRES      (BIT(CLOCK_REALTIME)            | \
                         BIT(CLOCK_MONOTONIC)           | \
@@ -145,9 +156,11 @@ extern struct vdso_rng_data _vdso_rng_data __attribute__((visibility("hidden")))
 #else
 extern struct vdso_time_data vdso_u_time_data[CS_BASES] __attribute__((visibility("hidden")));
 extern struct vdso_rng_data vdso_u_rng_data __attribute__((visibility("hidden")));
+extern struct vdso_arch_data vdso_u_arch_data __attribute__((visibility("hidden")));
 
 extern struct vdso_time_data *vdso_k_time_data;
 extern struct vdso_rng_data *vdso_k_rng_data;
+extern struct vdso_arch_data *vdso_k_arch_data;
 #endif
 
 /**
@@ -160,10 +173,15 @@ union vdso_data_store {
 
 #ifdef CONFIG_GENERIC_VDSO_DATA_STORE
 
+#define VDSO_ARCH_DATA_SIZE ALIGN(sizeof(struct vdso_arch_data), PAGE_SIZE)
+#define VDSO_ARCH_DATA_PAGES (VDSO_ARCH_DATA_SIZE >> PAGE_SHIFT)
+
 enum vdso_pages {
        VDSO_TIME_PAGE_OFFSET,
        VDSO_TIMENS_PAGE_OFFSET,
        VDSO_RNG_PAGE_OFFSET,
+       VDSO_ARCH_PAGES_START,
+       VDSO_ARCH_PAGES_END = VDSO_ARCH_PAGES_START + VDSO_ARCH_DATA_PAGES - 1,
        VDSO_NR_PAGES
 };
 
@@ -193,10 +211,17 @@ enum vdso_pages {
 #define __vdso_u_rng_data
 #endif
 
+#ifdef CONFIG_ARCH_HAS_VDSO_ARCH_DATA
+#define __vdso_u_arch_data     PROVIDE(vdso_u_arch_data = vdso_u_data + 3 * PAGE_SIZE);
+#else
+#define __vdso_u_arch_data
+#endif
+
 #define VDSO_VVAR_SYMS                                         \
        PROVIDE(vdso_u_data = . - __VDSO_PAGES * PAGE_SIZE);    \
        PROVIDE(vdso_u_time_data = vdso_u_data);                \
        __vdso_u_rng_data                                       \
+       __vdso_u_arch_data                                      \
 
 
 #endif /* !__ASSEMBLY__ */

diff --git a/lib/vdso/datastore.c b/lib/vdso/datastore.c
index 9260b00dc8520af109bd9dd05ac7f7504eafbea0..0959d62d78586ef458eb5f7c1e152f6b5d4cbf85 100644 (file)
--- a/lib/vdso/datastore.c
+++ b/lib/vdso/datastore.c
@@ -26,6 +26,14 @@ struct vdso_rng_data *vdso_k_rng_data = &vdso_rng_data_store.data;
 static_assert(sizeof(vdso_rng_data_store) == PAGE_SIZE);
 #endif /* CONFIG_VDSO_GETRANDOM */
 
+#ifdef CONFIG_ARCH_HAS_VDSO_ARCH_DATA
+static union {
+       struct vdso_arch_data   data;
+       u8                      page[VDSO_ARCH_DATA_SIZE];
+} vdso_arch_data_store __page_aligned_data;
+struct vdso_arch_data *vdso_k_arch_data = &vdso_arch_data_store.data;
+#endif /* CONFIG_ARCH_HAS_VDSO_ARCH_DATA */
+
 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
                             struct vm_area_struct *vma, struct vm_fault *vmf)
 {
@@ -67,6 +75,12 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
                        return VM_FAULT_SIGBUS;
                pfn = __phys_to_pfn(__pa_symbol(vdso_k_rng_data));
                break;
+       case VDSO_ARCH_PAGES_START ... VDSO_ARCH_PAGES_END:
+               if (!IS_ENABLED(CONFIG_ARCH_HAS_VDSO_ARCH_DATA))
+                       return VM_FAULT_SIGBUS;
+               pfn = __phys_to_pfn(__pa_symbol(vdso_k_arch_data)) +
+                       vmf->pgoff - VDSO_ARCH_PAGES_START;
+               break;
        default:
                return VM_FAULT_SIGBUS;
        }