linux-kernel - [RFC PATCH 0/7] x86/kexec: Add exception handling for relocate

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Message-ID: <20241103054019.3795299-1-dwmw2@infradead.org>
Date: Sun,  3 Nov 2024 05:35:25 +0000
From: David Woodhouse <dwmw2@...radead.org>
To: kexec@...ts.infradead.org
Cc: 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>
Subject: [RFC PATCH 0/7] x86/kexec: Add exception handling for relocate_kernel

Page faults in relocate_kernel() are extremely painful to debug. Provide a
basic exception handler which will just dump the exception information and
registers to a serial port.

It's disabled by default and has to be enabled with #define DEBUG.

While I was at it, I also stopped swap_pages from actually swapping pages
in the case of a plain kexec without preserve_context. Unless I'm missing
something, that's just a pointless waste of time.

David Woodhouse (7):
      x86/kexec: Clean up and document register use in relocate_kernel_64.S
      x86/kexec: Use named labels in swap_pages in relocate_kernel_64.S
      x86/kexec: Only swap pages for preserve_context mode
      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

 arch/x86/kernel/relocate_kernel_64.S | 265 ++++++++++++++++++++++++++++++++---
 1 file changed, 246 insertions(+), 19 deletions(-)