linux-kernel - Re: [PATCH v7 8/8] [DO NOT MERGE] x86/kexec: Add CFI type information to relocate

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Message-ID: <ra6zlx2iz7eks3y4ymoi6mn7o6rvnjc3lnjoaadf3szaocbkae@yg2lyjzlnqdn>
Date: Fri, 14 Mar 2025 09:07:58 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: David Woodhouse <dwmw2@...radead.org>
Cc: kexec@...ts.infradead.org, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>, 
	David Woodhouse <dwmw@...zon.co.uk>, "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>, 
	Kai Huang <kai.huang@...el.com>, Nikolay Borisov <nik.borisov@...e.com>, 
	linux-kernel@...r.kernel.org, Simon Horman <horms@...nel.org>, Dave Young <dyoung@...hat.com>, 
	Peter Zijlstra <peterz@...radead.org>, bsz@...zon.de
Subject: Re: [PATCH v7 8/8] [DO NOT MERGE] x86/kexec: Add CFI type
 information to relocate_kernel()

On Wed, Mar 12, 2025 at 02:34:20PM +0000, David Woodhouse wrote:
> From: David Woodhouse <dwmw@...zon.co.uk>
> 
> A previous commit added __nocfi to machine_kexec() because it makes an
> indirect call to relocate_kernel() which lacked CFI type information,
> and caused the system to crash.
> 
> Use SYM_TYPED_FUNC_START() to ensure that the type information is
> present, and remove the __nocfi tag.
> 
> I still can't make objtool happy with this in both GCC and Clang builds
> at the same time, so not yet for merging; only included in this series
> to nerd-snipe the objtool maintainers.

Again, I'd recommend just compiling the code in .data..relocate_kernel.
Then objtool doesn't need to care.

Otherwise it would help to know what warnings you're getting with this
patch, and the corresponding .config.

-- 
Josh