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From: Ard Biesheuvel <ardb@kernel.org>
To: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>,
	James Morris <jmorris@namei.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Anshuman Khandual <anshuman.khandual@arm.com>,
	Mike Rapoport <rppt@kernel.org>,
	Logan Gunthorpe <logang@deltatee.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/1] arm64: mm: correct the inside linear map boundaries during hotplug check
Date: Mon, 15 Feb 2021 20:34:26 +0100	[thread overview]
Message-ID: <CAMj1kXESuD-von_dtzYcUMwK7TLF=qTki9bd8_iTo_isBwj13g@mail.gmail.com> (raw)
In-Reply-To: <CA+CK2bA7Xz0Zg5phsQi3mhnp+_PHLAAGRLgFTQNw1FjBHaXsHA@mail.gmail.com>

On Mon, 15 Feb 2021 at 20:30, Pavel Tatashin <pasha.tatashin@soleen.com> wrote:
>
> > Can't we simply use signed arithmetic here? This expression works fine
> > if the quantities are all interpreted as s64 instead of u64
>
> I was thinking about that, but I do not like the idea of using sign
> arithmetics for physical addresses. Also, I am worried that someone in
> the future will unknowingly change it to unsigns or to phys_addr_t. It
> is safer to have start explicitly set to 0 in case of wrap.

memstart_addr is already a s64 for this exact reason.

Btw, the KASLR check is incorrect: memstart_addr could also be
negative when running the 52-bit VA kernel on hardware that is only
48-bit VA capable.

WARNING: multiple messages have this Message-ID (diff)
From: Ard Biesheuvel <ardb@kernel.org>
To: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	James Morris <jmorris@namei.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Logan Gunthorpe <logang@deltatee.com>,
	Tyler Hicks <tyhicks@linux.microsoft.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Will Deacon <will@kernel.org>, Mike Rapoport <rppt@kernel.org>
Subject: Re: [PATCH v2 1/1] arm64: mm: correct the inside linear map boundaries during hotplug check
Date: Mon, 15 Feb 2021 20:34:26 +0100	[thread overview]
Message-ID: <CAMj1kXESuD-von_dtzYcUMwK7TLF=qTki9bd8_iTo_isBwj13g@mail.gmail.com> (raw)
In-Reply-To: <CA+CK2bA7Xz0Zg5phsQi3mhnp+_PHLAAGRLgFTQNw1FjBHaXsHA@mail.gmail.com>

On Mon, 15 Feb 2021 at 20:30, Pavel Tatashin <pasha.tatashin@soleen.com> wrote:
>
> > Can't we simply use signed arithmetic here? This expression works fine
> > if the quantities are all interpreted as s64 instead of u64
>
> I was thinking about that, but I do not like the idea of using sign
> arithmetics for physical addresses. Also, I am worried that someone in
> the future will unknowingly change it to unsigns or to phys_addr_t. It
> is safer to have start explicitly set to 0 in case of wrap.

memstart_addr is already a s64 for this exact reason.

Btw, the KASLR check is incorrect: memstart_addr could also be
negative when running the 52-bit VA kernel on hardware that is only
48-bit VA capable.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-02-15 19:35 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-15 19:22 [PATCH v2 0/1] correct the inside linear map boundaries during hotplug check Pavel Tatashin
2021-02-15 19:22 ` Pavel Tatashin
2021-02-15 19:22 ` [PATCH v2 1/1] arm64: mm: " Pavel Tatashin
2021-02-15 19:22   ` Pavel Tatashin
2021-02-15 19:27   ` Ard Biesheuvel
2021-02-15 19:27     ` Ard Biesheuvel
2021-02-15 19:30     ` Pavel Tatashin
2021-02-15 19:30       ` Pavel Tatashin
2021-02-15 19:34       ` Ard Biesheuvel [this message]
2021-02-15 19:34         ` Ard Biesheuvel
2021-02-15 19:51         ` Pavel Tatashin
2021-02-15 19:51           ` Pavel Tatashin
2021-02-15 22:28           ` Pavel Tatashin
2021-02-15 22:28             ` Pavel Tatashin
2021-02-16  3:12           ` Anshuman Khandual
2021-02-16  3:12             ` Anshuman Khandual
2021-02-16  7:36             ` Ard Biesheuvel
2021-02-16  7:36               ` Ard Biesheuvel
2021-02-16 14:34               ` Pavel Tatashin
2021-02-16 14:34                 ` Pavel Tatashin
2021-02-16  2:55     ` Anshuman Khandual
2021-02-16  2:55       ` Anshuman Khandual
2021-02-16 14:48       ` Pavel Tatashin
2021-02-16 14:48         ` Pavel Tatashin

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