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From: Nick Terrell <terrelln@fb.com>
To: Petr Malat <oss@malat.biz>
Cc: Nick Terrell <nickrterrell@gmail.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Chris Mason <clm@fb.com>,
	"linux-kbuild@vger.kernel.org" <linux-kbuild@vger.kernel.org>,
	"x86@kernel.org" <x86@kernel.org>,
	"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	Kees Cook <keescook@chromium.org>,
	Kernel Team <Kernel-team@fb.com>,
	Adam Borowski <kilobyte@angband.pl>,
	Patrick Williams <patrickw3@fb.com>,
	Michael van der Westhuizen <rmikey@fb.com>,
	"mingo@kernel.org" <mingo@kernel.org>,
	Patrick Williams <patrick@stwcx.xyz>
Subject: Re: [PATCH v3 1/8] lib: prepare zstd for preboot environment
Date: Thu, 26 Mar 2020 18:50:43 +0000	[thread overview]
Message-ID: <40FFD6B5-8353-4126-9F89-B8F21A400EB3@fb.com> (raw)
In-Reply-To: <20200326154038.GA21231@ntb.petris.klfree.czf>



> On Mar 26, 2020, at 8:40 AM, Petr Malat <oss@malat.biz> wrote:
> 
> Hi Nick,
> I finally got some time to review your patch, here are my comments:
> 
> On Wed, Mar 25, 2020 at 12:58:42PM -0700, Nick Terrell wrote:
>> * Don't export symbols if ZSTD_PREBOOT is defined.
> I'm not sure if this is needed. When I worked on my patch, I have found that
> all exporting and modinfo macros generate symbols in modinfo and discard.ksym
> sections, which are then dropped by the vmlinux linker script, thus one
> will get the same binary independently if he puts this change in or not.
> 
> I'm not sure if this is intentional as there is also __DISABLE_EXPORTS define,
> which should be used by a decompressor (according to comments in export.h).

This is not my area of expertise, I’m a zstd developer not a kernel developer.
For that reason I wanted to pick the safe route of disabling the exports explicitly,
since that is what the other decompressors do, so I know it works.

If you’re confident that it isn’t necessary, I can drop the modification. But, I do
prefer this approach, because there is no magic involved. I can see what is
happening clearly just by looking at the decompress_unzstd.c code.

Thanks for the review,
Nick


  reply	other threads:[~2020-03-26 18:51 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-25 19:58 [PATCH v3 0/8] Add support for ZSTD-compressed kernel and initramfs Nick Terrell
2020-03-25 19:58 ` [PATCH v3 1/8] lib: prepare zstd for preboot environment Nick Terrell
2020-03-26 15:40   ` Petr Malat
2020-03-26 18:50     ` Nick Terrell [this message]
2020-03-25 19:58 ` [PATCH v3 2/8] lib: prepare xxhash " Nick Terrell
2020-03-25 19:58 ` [PATCH v3 3/8] lib: add zstd support to decompress Nick Terrell
2020-03-26 16:47   ` Petr Malat
2020-03-26 19:03     ` Nick Terrell
2020-03-26 20:16       ` Petr Malat
2020-03-26 21:13         ` Nick Terrell
2020-03-26 21:44           ` Petr Malat
2020-03-26 21:58             ` Nick Terrell
2020-04-01  2:46         ` Nick Terrell
2020-03-25 19:58 ` [PATCH v3 4/8] init: add support for zstd compressed kernel Nick Terrell
2020-03-25 19:58 ` [PATCH v3 5/8] usr: add support for zstd compressed initramfs Nick Terrell
2020-03-25 19:58 ` [PATCH v3 6/8] x86: bump ZO_z_extra_bytes margin for zstd Nick Terrell
2020-03-25 19:58 ` [PATCH v3 7/8] x86: Add support for ZSTD compressed kernel Nick Terrell
2020-03-25 19:58 ` [PATCH v3 8/8] .gitignore: add ZSTD-compressed files Nick Terrell
2020-03-25 20:10 ` [PATCH v3 0/8] Add support for ZSTD-compressed kernel and initramfs Kees Cook

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