From nobody Thu Dec 18 02:24:18 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A26C43451D1; Tue, 16 Dec 2025 07:45:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765871141; cv=none; b=ADxdphTUl8LIFOOskri2cH3N7rvy252P2D5lovSO8e8dcZc5/DaK/YJY2aVrD5gDQVJz0hAU7o+uRMwTi+LbWB2yg0ImHgZCDxHV7npySBvm3+jSh5aKFRJK2GJbQPk1CxceCBzXxkRe3PI+MEZmdUuocf3KWmTIJIueBk3Z7pU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765871141; c=relaxed/simple; bh=0i3zA22k2tG1Va0CvL4JeyMUaJv8xOEqU4aBTN2XJI8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=ApPPHxYzB7PZeDSnnjd4/g23jv1uyZ7JY8Es9RKZaraT7TK0mNiPIAb5e0MnqMkamMtFq+dan0PB3fadFVq5ml/2epGZ5sPkoJ7oZG3NABwTy1spqmWzlZE8B8QcEHQtpGeUeotD3qqC9MQ1kGYUpR2IPYZtlUmHTE/muOJDc4Y= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MuqKpd3m; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MuqKpd3m" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2993FC16AAE; Tue, 16 Dec 2025 07:45:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1765871141; bh=0i3zA22k2tG1Va0CvL4JeyMUaJv8xOEqU4aBTN2XJI8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MuqKpd3mB5mQ1zBY8bIwUOpI2XvNo6Llxdpn8YlmscUiwqRfbdjfpraiu6114/255 XvKCfzjjPEVi2nfyRDB6ETmQBGye4s1OownUP//68HzkC8/hoCX31tkbQONuBFhvzF fHRgm1iyGhKjFwJbhSn0bCg36q71wMnHtbS3wx/kgKixKr25c2vAHi7P3J8dAdsRre h1szOwf8v7ngPt6uRzCTYncIC+5X8ZXn6gPsQ6WXa/kXysM+f8ClT1RtPX5SLoVnH4 p+U56RN0+pdf+B9HCky95jert4jw559VTD4l836w4Zs5Bk5CARtxK9cW6B2L/x+Gwd aMnhX7+y0QtWQ== From: Jarkko Sakkinen To: linux-integrity@vger.kernel.org Cc: Jarkko Sakkinen , "David S . Miller" , Herbert Xu , Peter Huewe , Jason Gunthorpe , David Howells , Paul Moore , James Morris , "Serge E. Hallyn" , linux-kernel@vger.kernel.org (open list), keyrings@vger.kernel.org (open list:KEYS/KEYRINGS), linux-security-module@vger.kernel.org (open list:SECURITY SUBSYSTEM) Subject: [PATCH v7 09/12] tpm: Change tpm_get_random() opportunistic Date: Tue, 16 Dec 2025 09:44:50 +0200 Message-Id: <20251216074454.2192499-10-jarkko@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20251216074454.2192499-1-jarkko@kernel.org> References: <20251216074454.2192499-1-jarkko@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" hwrng framework does not have a requirement that the all bytes requested need to be provided. By enforcing such a requirement internally, TPM driver can cause unpredictability in latency, as a single tpm_get_random() call can result multiple TPM commands. Especially, when TCG_TPM2_HMAC is enabled, extra roundtrips could have significant effect to the system latency. Thus, send TPM command only once and return bytes received instead of committing to the number of requested bytes. Cc: David S. Miller Cc: Herbert Xu Signed-off-by: Jarkko Sakkinen --- v7: - Given that hwrng is now only caller for tpm_get_random(), remove the wait parameter. v4: - Fixed grammar mistakes. --- drivers/char/tpm/tpm-interface.c | 28 +++++----------------------- 1 file changed, 5 insertions(+), 23 deletions(-) diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interf= ace.c index d157be738612..677dcef05dfb 100644 --- a/drivers/char/tpm/tpm-interface.c +++ b/drivers/char/tpm/tpm-interface.c @@ -626,10 +626,6 @@ static int tpm2_get_random(struct tpm_chip *chip, u8 *= out, size_t max) */ int tpm_get_random(struct tpm_chip *chip, u8 *out, size_t max) { - u32 num_bytes =3D max; - u8 *out_ptr =3D out; - int retries =3D 5; - int total =3D 0; int rc; =20 if (!out || !max || max > TPM_MAX_RNG_DATA) @@ -646,28 +642,14 @@ int tpm_get_random(struct tpm_chip *chip, u8 *out, si= ze_t max) rc =3D tpm2_start_auth_session(chip); if (rc) return rc; - } - - do { - if (chip->flags & TPM_CHIP_FLAG_TPM2) - rc =3D tpm2_get_random(chip, out_ptr, num_bytes); - else - rc =3D tpm1_get_random(chip, out_ptr, num_bytes); - - if (rc < 0) - goto err; - - out_ptr +=3D rc; - total +=3D rc; - num_bytes -=3D rc; - } while (retries-- && total < max); =20 - tpm_put_ops(chip); - return total ? total : -EIO; + rc =3D tpm2_get_random(chip, out, max); + } else { + rc =3D tpm1_get_random(chip, out, max); + } =20 -err: tpm_put_ops(chip); - return rc; + return rc !=3D 0 ? rc : -EIO; } EXPORT_SYMBOL_GPL(tpm_get_random); =20 --=20 2.39.5