linux-kernel - [PATCH 3/9] vdso: Add __arch_get_k_vdso_rng

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Message-ID: <a7bdbbb14d8635c1e33ada7982cf2cd1a8321e5c.1723817900.git.christophe.leroy@csgroup.eu>
Date: Fri, 16 Aug 2024 16:36:50 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Naveen N Rao <naveen@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	"Theodore Ts'o" <tytso@....edu>,
	"Jason A. Donenfeld" <Jason@...c4.com>,
	Andy Lutomirski <luto@...nel.org>,
	Vincenzo Frascino <vincenzo.frascino@....com>,
	Arnd Bergmann <arnd@...db.de>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	linux-arch@...r.kernel.org
Subject: [PATCH 3/9] vdso: Add __arch_get_k_vdso_rng_data()

_vdso_data is specific to x86 and __arch_get_k_vdso_data() is provided
so that all architectures can provide the requested pointer.

Do the same with _vdso_rng_data, provide __arch_get_k_vdso_rng_data()
and don't use x86 _vdso_rng_data directly.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/x86/include/asm/vdso/vsyscall.h | 7 +++++++
 drivers/char/random.c                | 5 +++--
 include/asm-generic/vdso/vsyscall.h  | 7 +++++++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/vdso/vsyscall.h b/arch/x86/include/asm/vdso/vsyscall.h
index 972415a8be31..92b85189b8fe 100644
--- a/arch/x86/include/asm/vdso/vsyscall.h
+++ b/arch/x86/include/asm/vdso/vsyscall.h
@@ -22,6 +22,13 @@ struct vdso_data *__x86_get_k_vdso_data(void)
 }
 #define __arch_get_k_vdso_data __x86_get_k_vdso_data
 
+static __always_inline
+struct vdso_rng_data *__x86_get_k_vdso_rng_data(void)
+{
+	return &_vdso_rng_data;
+}
+#define __arch_get_k_vdso_rng_data __x86_get_k_vdso_rng_data
+
 /* The asm-generic header needs to be included after the definitions above */
 #include <asm-generic/vdso/vsyscall.h>
 
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 87fe61295ea1..77968309e2c2 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -59,6 +59,7 @@
 #ifdef CONFIG_VDSO_GETRANDOM
 #include <vdso/getrandom.h>
 #include <vdso/datapage.h>
+#include <vdso/vsyscall.h>
 #endif
 #include <asm/archrandom.h>
 #include <asm/processor.h>
@@ -282,7 +283,7 @@ static void crng_reseed(struct work_struct *work)
 	 * is ordered with the write above to base_crng.generation. Pairs with
 	 * the smp_rmb() before the syscall in the vDSO code.
 	 */
-	smp_store_release(&_vdso_rng_data.generation, next_gen + 1);
+	smp_store_release(&__arch_get_k_vdso_rng_data()->generation, next_gen + 1);
 #endif
 	if (!static_branch_likely(&crng_is_ready))
 		crng_init = CRNG_READY;
@@ -735,7 +736,7 @@ 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(_vdso_rng_data.is_ready, true);
+		WRITE_ONCE(__arch_get_k_vdso_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 c835607f78ae..d44a828e34a4 100644
--- a/include/asm-generic/vdso/vsyscall.h
+++ b/include/asm-generic/vdso/vsyscall.h
@@ -11,6 +11,13 @@ static __always_inline struct vdso_data *__arch_get_k_vdso_data(void)
 }
 #endif /* __arch_get_k_vdso_data */
 
+#ifndef __arch_get_k_vdso_rng_data
+static __always_inline struct vdso_rng_data *__arch_get_k_vdso_rng_data(void)
+{
+	return NULL;
+}
+#endif /* __arch_get_k_vdso_rng_data */
+
 #ifndef __arch_update_vsyscall
 static __always_inline void __arch_update_vsyscall(struct vdso_data *vdata,
 						   struct timekeeper *tk)
-- 
2.44.0