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Tue, 14 Oct 2025 17:49:22 +1100 (AEDT) From: =?utf-8?q?Thomas_Wei=C3=9Fschuh?= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1760424558; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pR/zA7NHuz/iSgfuExTYGBCAYU1piUOghds7Ej4rutQ=; b=xwpgAjCw/ps+pinXuuk2/1dUDVRTBDHyfrLLMo8MlWkHEttiN3Lme9z3POyxQgkpIBnlH2 bfPLMPbmonasAP8/h3DqUcWmWdTXpcMp+PURdY/aodql4tRR7iLuAfceTvw5qLAfvhNUi9 kjFwk/qplrwr+RHSIqMxc1sefFqio7IBE1qrCch3a5MvboPVK+rdu1F2vR2lBsOdw2DFmF vn/v76sttztESWoDAoBxDE20ZNauwK6nlVs303NrJpH7lTfqX1lHGkoz7dU38hNgNyutWX 7seC/Ivqdv/wEqDL7QgRy/it5N0QMmlz7ca94RhyOuyknwXYeKlBwVSBOPaZwA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1760424558; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pR/zA7NHuz/iSgfuExTYGBCAYU1piUOghds7Ej4rutQ=; b=YFGw/5OTU7+qFg7O1bPcZy+A26sSqbjmgTFySDLn8C+zWb7h8CXgac6r1GEKgHexeNhCWM Rt5a8gCQztnFyzDw== Date: Tue, 14 Oct 2025 08:49:04 +0200 Subject: [PATCH v4 18/35] random: vDSO: split out datapage update into helper functions X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Message-Id: <20251014-vdso-sparc64-generic-2-v4-18-e0607bf49dea@linutronix.de> References: <20251014-vdso-sparc64-generic-2-v4-0-e0607bf49dea@linutronix.de> In-Reply-To: <20251014-vdso-sparc64-generic-2-v4-0-e0607bf49dea@linutronix.de> To: Andy Lutomirski , Thomas Gleixner , Vincenzo Frascino , Arnd Bergmann , "David S. Miller" , Andreas Larsson , Nick Alcock , John Stultz , Stephen Boyd , John Paul Adrian Glaubitz , Shuah Khan , Catalin Marinas , Will Deacon , Theodore Ts'o , "Jason A. Donenfeld" , Russell King , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Nagarathnam Muthusamy , Shannon Nelson Cc: linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-s390@vger.kernel.org, =?utf-8?q?Thomas_Wei=C3=9Fschuh?= X-Developer-Signature: v=1; a=ed25519-sha256; t=1760424546; l=3858; i=thomas.weissschuh@linutronix.de; s=20240209; h=from:subject:message-id; bh=Yjs06k6xtXBqaQesLwEwImUgnZrxr+a65u05KeyUpws=; b=Z/fYMJVpB38ZTotx7ngQAg3m8vGxBbu5vNnNCk1ITkJ/S1Sy7ZizJ/fsfLPddfumk6a8XDGxg z6DZxy1Cm6ICrTMT0W+xc8eyJIN6lJAMQL3zaONjy9S1b8GrM/mVYP5 X-Developer-Key: i=thomas.weissschuh@linutronix.de; a=ed25519; pk=pfvxvpFUDJV2h2nY0FidLUml22uGLSjByFbM6aqQQws= Some upcoming changes will introduce additional callers of them. Signed-off-by: Thomas Weißschuh Tested-by: Andreas Larsson Reviewed-by: Andreas Larsson --- drivers/char/random.c | 51 +++++++++++++++++++++++++++++++++------------------ 1 file changed, 33 insertions(+), 18 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index b0b88c6f6a1afcdb770e39b7a64cb3408e33bd2c..73c53a4fb949bfd2ed723fa3cec3fe0d066a7fa3 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -246,6 +246,37 @@ static unsigned int crng_reseed_interval(void) /* Used by crng_reseed() and crng_make_state() to extract a new seed from the input pool. */ static void extract_entropy(void *buf, size_t len); +/* This updates the generation in the vDSO data page */ +static void random_vdso_update_generation(unsigned long next_gen) +{ + if (!IS_ENABLED(CONFIG_VDSO_GETRANDOM)) + return; + + /* base_crng.generation's invalid value is ULONG_MAX, while + * 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. + * + * Cast to unsigned long for 32-bit architectures, since atomic 64-bit + * operations are not supported on those architectures. This is safe + * because base_crng.generation is a 32-bit value. On big-endian + * architectures it will be stored in the upper 32 bits, but that's okay + * because the vDSO side only checks whether the value changed, without + * actually using or interpreting the value. + */ + smp_store_release((unsigned long *)&vdso_k_rng_data->generation, next_gen + 1); +} + +/* This sets is_ready in the vDSO data page */ +static void random_vdso_set_ready(void) +{ + if (!IS_ENABLED(CONFIG_VDSO_GETRANDOM)) + return; + + WRITE_ONCE(vdso_k_rng_data->is_ready, true); +} + /* This extracts a new crng key from the input pool. */ static void crng_reseed(struct work_struct *work) { @@ -272,22 +303,7 @@ static void crng_reseed(struct work_struct *work) if (next_gen == ULONG_MAX) ++next_gen; WRITE_ONCE(base_crng.generation, next_gen); - - /* base_crng.generation's invalid value is ULONG_MAX, while - * 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. - * - * Cast to unsigned long for 32-bit architectures, since atomic 64-bit - * operations are not supported on those architectures. This is safe - * because base_crng.generation is a 32-bit value. On big-endian - * architectures it will be stored in the upper 32 bits, but that's okay - * because the vDSO side only checks whether the value changed, without - * actually using or interpreting the value. - */ - if (IS_ENABLED(CONFIG_VDSO_GETRANDOM)) - smp_store_release((unsigned long *)&vdso_k_rng_data->generation, next_gen + 1); + random_vdso_update_generation(next_gen); if (!static_branch_likely(&crng_is_ready)) crng_init = CRNG_READY; @@ -741,8 +757,7 @@ static void __cold _credit_init_bits(size_t bits) if (static_key_initialized && system_unbound_wq) queue_work(system_unbound_wq, &set_ready); atomic_notifier_call_chain(&random_ready_notifier, 0, NULL); - if (IS_ENABLED(CONFIG_VDSO_GETRANDOM)) - WRITE_ONCE(vdso_k_rng_data->is_ready, true); + random_vdso_set_ready(); wake_up_interruptible(&crng_init_wait); kill_fasync(&fasync, SIGIO, POLL_IN); pr_notice("crng init done\n"); -- 2.51.0