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bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, tmgross@umich.edu, dakr@kernel.org Cc: linux-mm@kvack.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] rust: Test page_align usize::MAX boundary edges Message-ID: References: <20251230094841.76830-1-bshephar@bne-home.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251230094841.76830-1-bshephar@bne-home.net> X-Proofpoint-ORIG-GUID: eDq-KvX5c89fLpQ15zl4qfk3YuBty3Qi X-Authority-Info: v=2.4 cv=OZuVzxTY c=1 sm=1 tr=0 ts=6953a18a cx=c_apl:c_pps a=YrL12D//S6tul8v/L+6tKg==:117 a=YrL12D//S6tul8v/L+6tKg==:17 a=kj9zAlcOel0A:10 a=wP3pNCr1ah4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=pGLkceISAAAA:8 a=JppZAXPjAAAA:8 a=v0bcC3016m_wzupuhzUA:9 a=CjuIK1q_8ugA:10 a=mTXuAFqUwmiQvsSFmwXH:22 X-Proofpoint-GUID: eDq-KvX5c89fLpQ15zl4qfk3YuBty3Qi X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMjMwMDA4OSBTYWx0ZWRfX5PILfIQ/g32F 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 vjq35pJi 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> "[PATCH v8] rust: Return Option from page_align and ensure no usize overflow" > > Signed-off-by: Brendan Shephard > --- > rust/kernel/page.rs | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs > index adecb200c654..d602d4231f56 100644 > --- a/rust/kernel/page.rs > +++ b/rust/kernel/page.rs > @@ -45,9 +45,10 @@ > /// assert_eq!(page_align(0x1), Some(PAGE_SIZE)); > /// assert_eq!(page_align(PAGE_SIZE + 1), Some(2 * PAGE_SIZE)); > /// > -/// // Requested address causes overflow (returns `None`). > -/// let overflow_addr = usize::MAX - (PAGE_SIZE / 2); > -/// assert_eq!(page_align(overflow_addr), None); > +/// // Testing boundary conditions at the end of the address space. > +/// assert_eq!(page_align(usize::MAX - PAGE_SIZE + 1), Some(usize::MAX - PAGE_SIZE + 1)); > +/// assert_eq!(page_align(usize::MAX - PAGE_SIZE + 2), None); > +/// assert_eq!(page_align(usize::MAX), None); > /// ``` > #[inline(always)] > pub const fn page_align(addr: usize) -> Option { > > base-commit: 7acc70476f14661149774ab88d3fe23d83ba4249 > -- > 2.52.0 > @miguel, Thanks for the pointers in: https://lore.kernel.org/all/CANiq72kcMLXz=xyZeKC0=j_e0BzJEY3wGpBTTxfJsc6EZhCnXA@mail.gmail.com/ https://lore.kernel.org/rust-for-linux/CANiq72mLPvB_6Ow3bW5-V4-km=RyA59chQ1g1x9qUt2P-zZweg@mail.gmail.com/ Let me know if this addresses the points you were raising in those. Maybe you just wanted usize::MAX and then one over? The first test case might be unnecessary. The last two do a fine job of illustrating the point I think.