linux-kernel - Re: [PATCH v7 0/8] x86/kexec: Add exception handling for relocate

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Z9K3dcMAgu3cot85@gmail.com>
Date: Thu, 13 Mar 2025 11:46:13 +0100
From: Ingo Molnar <mingo@...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>, jpoimboe@...nel.org,
	bsz@...zon.de
Subject: Re: [PATCH v7 0/8] x86/kexec: Add exception handling for
 relocate_kernel


* David Woodhouse <dwmw2@...radead.org> wrote:

> Debugging kexec failures is painful, as anything going wrong in execution
> of the critical relocate_kernel() function tends to just lead to a triple
> fault. Thus leading to *weeks* of my life that I won't get back. Having
> hacked something up for my own use, I figured I should share it...
> 
> Add a trivial exception handler in the relocate_kernel environment which 
> outputs to the early_printk serial console if configured. Currently only 
> 8250-compatible serial ports are supported, but that could be extended.
> 
> I had to hack up QEMU support for a PCI serial port which matches what
> the existing early_printk code can drive, and the *real* 8250_pci driver
> doesn't seem to cope with that setup at all, but whatever... the kexec
> code now drives the same 32-bit stride which is all that earlyprintk
> supports. We can always add more later, if anyone cares.
> 
> Someone who cares might want to bring the i386 version into line with
> this, although the lack of rip-based addressing makes all the PIC code a
> bit harder.
> 
> David Woodhouse (8):
>       x86/kexec: Debugging support: load a GDT
>       x86/kexec: Debugging support: Load an IDT and basic exception entry points
>       x86/kexec: Debugging support: Dump registers on exception
>       x86/kexec: Add 8250 serial port output
>       x86/kexec: Add 8250 MMIO serial port output
>       x86/kexec: Invalidate GDT/IDT from relocate_kernel() instead of earlier
>       [DO NOT MERGE] x86/kexec: Add int3 in kexec path for testing
>       [DO NOT MERGE] x86/kexec: Add CFI type information to relocate_kernel()
> 
>  arch/x86/include/asm/kexec.h         |   7 ++
>  arch/x86/kernel/early_printk.c       |   9 ++
>  arch/x86/kernel/machine_kexec_64.c   |  50 ++++++--
>  arch/x86/kernel/relocate_kernel_64.S | 254 +++++++++++++++++++++++++++++++++++++++-
>  4 files changed, 308 insertions(+), 12 deletions(-)

I applied the first 3 patches to tip:x86/boot for phased-risk-reduction 
reasons, and because I had some questions and suggestions starting at 
patch #4.

Thanks,

	Ingo