linux-kernel - Re: [PATCH v2 3/3] x86: fix .brk attribute in linker script

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Message-ID: <20220629171829.shotpln44nzgo2eu@treble>
Date:   Wed, 29 Jun 2022 10:18:29 -0700
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Juergen Gross <jgross@...e.com>
Cc:     xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 3/3] x86: fix .brk attribute in linker script

On Thu, Jun 23, 2022 at 11:46:08AM +0200, Juergen Gross wrote:
> Commit e32683c6f7d2 ("x86/mm: Fix RESERVE_BRK() for older binutils")
> added the "NOLOAD" attribute to the .brk section as a "failsafe"
> measure.
> 
> Unfortunately this leads to the linker no longer covering the .brk
> section in a program header, resulting in the kernel loader not knowing
> that the memory for the .brk section must be reserved.
> 
> This has led to crashes when loading the kernel as PV dom0 under Xen,
> but other scenarios could be hit by the same problem (e.g. in case an
> uncompressed kernel is used and the initrd is placed directly behind
> it).
> 
> So drop the "NOLOAD" attribute. This has been verified to correctly
> cover the .brk section by a program header of the resulting ELF file.
> 
> Fixes: e32683c6f7d2 ("x86/mm: Fix RESERVE_BRK() for older binutils")
> Signed-off-by: Juergen Gross <jgross@...e.com>

Reviewed-by: Josh Poimboeuf <jpoimboe@...nel.org>

-- 
Josh