[PATCH v3 06/18] vdso: Add generic random data storage
From: Thomas Weißschuh <hidden>
Date: 2025-02-04 12:06:11
Also in:
linux-arch, linux-arm-kernel, linux-mips, linux-riscv, linux-s390, lkml, loongarch
Subsystem:
generic include/asm header files, generic vdso library, library code, random number driver, the rest · Maintainers:
Arnd Bergmann, Andy Lutomirski, Thomas Gleixner, Vincenzo Frascino, Andrew Morton, "Theodore Ts'o", Jason A. Donenfeld, Linus Torvalds
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 <redacted> --- drivers/char/random.c | 6 +++--- include/asm-generic/vdso/vsyscall.h | 12 ++++++++++++ include/vdso/datapage.h | 10 ++++++++++ lib/vdso/datastore.c | 14 ++++++++++++++ lib/vdso/getrandom.c | 8 ++++++-- 5 files changed, 45 insertions(+), 5 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 2581186fa61b7b278916a27f99ee22b4851dc37a..92cbd24a36d8c73ac6a17e8e787eeae3f6af1922 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c@@ -278,7 +278,7 @@ static void crng_reseed(struct work_struct *work) WRITE_ONCE(base_crng.generation, next_gen); #ifdef CONFIG_VDSO_GETRANDOM /* base_crng.generation's invalid value is ULONG_MAX, while - * _vdso_rng_data.generation's invalid value is 0, so add one to the + * vdso_k_rng_data->generation's invalid value is 0, so add one to the * former to arrive at the latter. Use smp_store_release so that this * is ordered with the write above to base_crng.generation. Pairs with * the smp_rmb() before the syscall in the vDSO code.
@@ -290,7 +290,7 @@ static void crng_reseed(struct work_struct *work) * because the vDSO side only checks whether the value changed, without * actually using or interpreting the value. */ - smp_store_release((unsigned long *)&__arch_get_k_vdso_rng_data()->generation, next_gen + 1); + smp_store_release((unsigned long *)&vdso_k_rng_data->generation, next_gen + 1); #endif if (!static_branch_likely(&crng_is_ready)) crng_init = CRNG_READY;
@@ -743,7 +743,7 @@ static void __cold _credit_init_bits(size_t bits) queue_work(system_unbound_wq, &set_ready); atomic_notifier_call_chain(&random_ready_notifier, 0, NULL); #ifdef CONFIG_VDSO_GETRANDOM - WRITE_ONCE(__arch_get_k_vdso_rng_data()->is_ready, true); + WRITE_ONCE(vdso_k_rng_data->is_ready, true); #endif wake_up_interruptible(&crng_init_wait); kill_fasync(&fasync, SIGIO, POLL_IN);
diff --git a/include/asm-generic/vdso/vsyscall.h b/include/asm-generic/vdso/vsyscall.h
index ac5b93b91993224da245e80031b9f51e0c083f3c..a5f973e4e2723ef1815c88a7846f7c477e3febd9 100644
--- a/include/asm-generic/vdso/vsyscall.h
+++ b/include/asm-generic/vdso/vsyscall.h@@ -13,6 +13,13 @@ static __always_inline const struct vdso_time_data *__arch_get_vdso_u_time_data( } #endif +#ifndef __arch_get_vdso_u_rng_data +static __always_inline const struct vdso_rng_data *__arch_get_vdso_u_rng_data(void) +{ + return &vdso_u_rng_data; +} +#endif + #else /* !CONFIG_GENERIC_VDSO_DATA_STORE */ #ifndef __arch_get_k_vdso_data
@@ -25,6 +32,11 @@ static __always_inline struct vdso_data *__arch_get_k_vdso_data(void) #define __arch_get_vdso_u_time_data __arch_get_vdso_data +#ifndef __arch_get_vdso_u_rng_data +#define __arch_get_vdso_u_rng_data() __arch_get_vdso_rng_data() +#endif +#define vdso_k_rng_data __arch_get_k_vdso_rng_data() + #endif /* CONFIG_GENERIC_VDSO_DATA_STORE */ #ifndef __arch_update_vsyscall
diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
index b3d8087488ff35fbbc4d5058ae21e2c6cc58ed9c..7dbc8797e3b8923c06f4b6b34790766e68b2abd2 100644
--- a/include/vdso/datapage.h
+++ b/include/vdso/datapage.h@@ -144,8 +144,10 @@ extern struct vdso_time_data _timens_data[CS_BASES] __attribute__((visibility("h 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_time_data *vdso_k_time_data; +extern struct vdso_rng_data *vdso_k_rng_data; #endif /**
@@ -161,6 +163,7 @@ union vdso_data_store { enum vdso_pages { VDSO_TIME_PAGE_OFFSET, VDSO_TIMENS_PAGE_OFFSET, + VDSO_RNG_PAGE_OFFSET, VDSO_NR_PAGES };
@@ -184,9 +187,16 @@ enum vdso_pages { #else /* !__ASSEMBLY__ */ +#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_rng_data \ #endif /* !__ASSEMBLY__ */
diff --git a/lib/vdso/datastore.c b/lib/vdso/datastore.c
index d3181768424cc3ee2e980bd537ac5ca14dfcb304..9260b00dc8520af109bd9dd05ac7f7504eafbea0 100644
--- a/lib/vdso/datastore.c
+++ b/lib/vdso/datastore.c@@ -17,6 +17,15 @@ struct vdso_time_data *vdso_k_time_data = vdso_time_data_store.data; static_assert(sizeof(vdso_time_data_store) == PAGE_SIZE); #endif /* CONFIG_HAVE_GENERIC_VDSO */ +#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) {
@@ -53,6 +62,11 @@ 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; }
diff --git a/lib/vdso/getrandom.c b/lib/vdso/getrandom.c
index 938ca539aaa64bc46280ef6dd17aa661126699eb..440f8a6203a69a6462aafee4ad8d5670cef6a353 100644
--- a/lib/vdso/getrandom.c
+++ b/lib/vdso/getrandom.c@@ -12,6 +12,9 @@ #include <uapi/linux/mman.h> #include <uapi/linux/random.h> +/* Bring in default accessors */ +#include <vdso/vsyscall.h> + #undef PAGE_SIZE #undef PAGE_MASK #define PAGE_SIZE (1UL << CONFIG_PAGE_SHIFT)
@@ -152,7 +155,7 @@ __cvdso_getrandom_data(const struct vdso_rng_data *rng_info, void *buffer, size_ /* * Prevent the syscall from being reordered wrt current_generation. Pairs with the - * smp_store_release(&_vdso_rng_data.generation) in random.c. + * smp_store_release(&vdso_k_rng_data->generation) in random.c. */ smp_rmb();
@@ -256,5 +259,6 @@ __cvdso_getrandom_data(const struct vdso_rng_data *rng_info, void *buffer, size_ static __always_inline ssize_t __cvdso_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len) { - return __cvdso_getrandom_data(__arch_get_vdso_rng_data(), buffer, len, flags, opaque_state, opaque_len); + return __cvdso_getrandom_data(__arch_get_vdso_u_rng_data(), buffer, len, flags, + opaque_state, opaque_len); }
--
2.48.1