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h=From:From:Date:Date:Subject:Subject:MIME-Version:Content-Type:Content-Transfer-Encoding:Message-Id:Message-Id:In-Reply-To:To:To:Cc:Cc:Reply-To; bh=1zUR5GEK6BA5S7bCITK+tOcim+IiL0R8T8uB3uRypFw=; b=DBJaNnN0xwPmmWzktPGNzvjxbQglRv47/8iJ7FWqpBQOw4gHUmy7gIbQJhUU03lk RonFSD4Z1vcxW+YuMkqs2rphAy6U49uknah/CSOTlxyLW/EcTW2B29LRF+y9T/QRaTD jT9QnfSkQJIqo+ysgWF67Po7XGdSa7ilClojNbAE= Received: by smtp.zohomail.com with SMTPS id 179254121012077.48844824785681; Tue, 20 Oct 2026 17:06:50 -0700 (PDT) From: Deborah Brouwer Date: Tue, 20 Oct 2026 17:06:47 -0700 Subject: [PATCH v4 3/3] drm/tyr: allow userspace buffers to be mismatched X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261020-b4-dev_query_fixes-v4-3-df66b4c98bc6@collabora.com> References: <20261020-b4-dev_query_fixes-v4-0-df66b4c98bc6@collabora.com> In-Reply-To: <20261020-b4-dev_query_fixes-v4-0-df66b4c98bc6@collabora.com> To: Miguel Ojeda , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , =?utf-8?q?Onur_=C3=96zkan?= , David Airlie , Simona Vetter Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Deborah Brouwer X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=3093; i=deborah.brouwer@collabora.com; h=from:subject:message-id; bh=cw/gH4gJ7P+GmpjRc8el+UvRXUZRj4b9UKEbdATligI=; b=owGbwMvMwCVWuULzOU9c7WvG02pJDFk3mERnajzZ/E6LRUzhsr5DqkaYW2vLl7d7Vn3/3aBVr 7BbRTSoo5SFQYyLQVZMkeWsvVGPeNV7I935/5th5rAygQxh4OIUgImkBzMyfHR5s5GXZes+8dNe O948t0+dFbpNuejaheo73FVFlmVPtjAyHN3KwRSxYbPw8dUPxX7zFzBLdOZqBqceXNzKf+InV6E JGwA= X-Developer-Key: i=deborah.brouwer@collabora.com; a=openpgp; fpr=CD3F328C177AEF322D9FFF8379A829E70C5E7DEB Allow userspace to provide a buffer that is smaller or larger than the object that the kernel expects to write into it. Set a minimum buffer size to match those in PANTHOR_UOBJ_MIN_SIZE. If userspace provides at least the minimum buffer size, then simply write until the buffer is full. If userspace provides a larger buffer than necessary, then zero out the remaining buffer. This ensures UAPI compatibility with Panthor. Signed-off-by: Deborah Brouwer --- drivers/gpu/drm/tyr/file.rs | 49 +++++++++++++++++++++++++++++++++++++-------- 1 file changed, 41 insertions(+), 8 deletions(-) diff --git a/drivers/gpu/drm/tyr/file.rs b/drivers/gpu/drm/tyr/file.rs index ceadde976502..bf66238ea4c6 100644 --- a/drivers/gpu/drm/tyr/file.rs +++ b/drivers/gpu/drm/tyr/file.rs @@ -1,14 +1,18 @@ // SPDX-License-Identifier: GPL-2.0 or MIT +use core::mem::offset_of; + use kernel::{ drm::{ self, Registered, // }, + num::casts::FromSafeCast, prelude::*, uaccess::UserSlice, uapi, // }; +use zerocopy::Immutable; use crate::driver::{ TyrDrmDevice, @@ -16,6 +20,37 @@ TyrDrmRegistrationData, // }; +trait UobjMinSize { + fn min_size(&self) -> usize; +} + +impl UobjMinSize for uapi::drm_panthor_gpu_info { + fn min_size(&self) -> usize { + offset_of!(Self, tiler_present) + size_of_val(&self.tiler_present) + } +} + +// If the user buffer is at least the minimum required size, then +// copy as much of the kernel object as will fit into the user buffer. +// Don't fail if the user buffer is smaller than the kernel object. +// If the user buffer is bigger than needed, zero out the remainder. +fn set_uobj( + usr_dst: u64, + size: u32, + min_size: usize, + src_obj: &T, +) -> Result { + let size = usize::from_safe_cast(size); + if size < min_size { + return Err(EINVAL); + } + + let mut writer = UserSlice::new(UserPtr::from_u64(usr_dst), size).writer(); + writer.write_slice_partial(src_obj.as_bytes(), 0)?; + writer.clear()?; + Ok(()) +} + #[pin_data] pub(crate) struct TyrDrmFileData {} @@ -48,14 +83,12 @@ pub(crate) fn dev_query( } else { match devquery.type_ { uapi::drm_panthor_dev_query_type_DRM_PANTHOR_DEV_QUERY_GPU_INFO => { - let mut writer = UserSlice::new( - UserPtr::from_addr(devquery.pointer as usize), - devquery.size as usize, - ) - .writer(); - - writer.write_slice(reg_data.gpu_info.as_bytes())?; - + set_uobj( + devquery.pointer, + devquery.size, + reg_data.gpu_info.min_size(), + ®_data.gpu_info, + )?; Ok(0) } _ => Err(EINVAL), -- 2.56.0