[PATCH 04/17] vdso: Add generic random data storage

[Thomas Weißschuh]

Extend the generic vDSO data storage with a page for the random state data.
The random state data is stored in a dedicated page, as the existing
storage page is only meant for time-related, time-namespace-aware data.
This simplifies to access logic to not need to handle time namespaces
anymore and also frees up more space in the time-related page.

In case further generic vDSO data store is required it can be added to
the random state page.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh at linutronix.de>
---
 include/vdso/datapage.h     | 24 ++++++++++++++++++++++++
 lib/vdso_kernel/datastore.c | 14 ++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
index 69af424413db1f265607d0f1bdbf88550548c5ba..5ce322422fcb7ba77aeafddbf132fd3e5dbc5a0c 100644
--- a/include/vdso/datapage.h
+++ b/include/vdso/datapage.h
@@ -145,8 +145,10 @@ extern struct vdso_rng_data _vdso_rng_data __attribute__((visibility("hidden")))
 #else
 extern const struct vdso_time_data vdso_u_time_data[CS_BASES] __attribute__((visibility("hidden")));
 extern const struct vdso_time_data vdso_u_timens_data[CS_BASES] __attribute__((visibility("hidden")));
+extern const struct vdso_rng_data vdso_u_rng_data __attribute__((visibility("hidden")));
 
 extern struct vdso_time_data *vdso_k_time_data;
+extern struct vdso_rng_data *vdso_k_rng_data;
 #endif
 
 /**
@@ -162,6 +164,7 @@ union vdso_data_store {
 enum vdso_pages {
 	VDSO_TIME_PAGE_OFFSET,
 	VDSO_TIMENS_PAGE_OFFSET,
+	VDSO_RNG_PAGE_OFFSET,
 	VDSO_NR_PAGES
 };
 
@@ -185,6 +188,20 @@ static __always_inline const struct vdso_time_data *__arch_get_vdso_u_timens_dat
 #define __arch_get_timens_vdso_data(vd) __arch_get_vdso_u_timens_data()
 #endif /* CONFIG_TIME_NS */
 
+#ifdef CONFIG_VDSO_GETRANDOM
+static __always_inline const struct vdso_rng_data *__arch_get_vdso_u_rng_data(void)
+{
+	return &vdso_u_rng_data;
+}
+#define __arch_get_vdso_rng_data __arch_get_vdso_u_rng_data
+
+static __always_inline struct vdso_rng_data *__arch_get_vdso_k_rng_data(void)
+{
+	return vdso_k_rng_data;
+}
+#define __arch_get_k_vdso_rng_data __arch_get_vdso_k_rng_data
+#endif /* CONFIG_VDSO_GETRANDOM */
+
 #endif /* CONFIG_GENERIC_VDSO_DATA_STORE */
 
 /*
@@ -211,10 +228,17 @@ static __always_inline const struct vdso_time_data *__arch_get_vdso_u_timens_dat
 #define __vdso_u_timens_data
 #endif
 
+#ifdef CONFIG_VDSO_GETRANDOM
+#define __vdso_u_rng_data	PROVIDE(vdso_u_rng_data = vdso_u_data + 2 * PAGE_SIZE);
+#else
+#define __vdso_u_rng_data
+#endif
+
 #define VDSO_VVAR_SYMS						\
 	PROVIDE(vdso_u_data = . - __VDSO_PAGES * PAGE_SIZE);	\
 	PROVIDE(vdso_u_time_data = vdso_u_data);		\
 	__vdso_u_timens_data					\
+	__vdso_u_rng_data					\
 
 
 #endif /* !__ASSEMBLY__ */
diff --git a/lib/vdso_kernel/datastore.c b/lib/vdso_kernel/datastore.c
index c9cd269b1ed1b6cdd5fdf9fe929d0b778314b962..0d4f5317b508a54b4f3295f0335d1eefce74d78c 100644
--- a/lib/vdso_kernel/datastore.c
+++ b/lib/vdso_kernel/datastore.c
@@ -15,6 +15,15 @@ static union vdso_data_store vdso_time_data_store __page_aligned_data;
 struct vdso_time_data *vdso_k_time_data = vdso_time_data_store.data;
 static_assert(sizeof(vdso_time_data_store) == PAGE_SIZE);
 
+#ifdef CONFIG_VDSO_GETRANDOM
+static union {
+	struct vdso_rng_data	data;
+	u8			page[PAGE_SIZE];
+} vdso_rng_data_store __page_aligned_data;
+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 */
+
 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 			     struct vm_area_struct *vma, struct vm_fault *vmf)
 {
@@ -49,6 +58,11 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 			return VM_FAULT_SIGBUS;
 		pfn = __phys_to_pfn(__pa_symbol(vdso_k_time_data));
 		break;
+	case VDSO_RNG_PAGE_OFFSET:
+		if (!IS_ENABLED(CONFIG_VDSO_GETRANDOM))
+			return VM_FAULT_SIGBUS;
+		pfn = __phys_to_pfn(__pa_symbol(vdso_k_rng_data));
+		break;
 	default:
 		return VM_FAULT_SIGBUS;
 	}

-- 
2.47.1