Message-ID: <20250109140757.2841269-1-dwmw2@infradead.org>
Date: Thu,  9 Jan 2025 14:04:12 +0000
From: David Woodhouse <dwmw2@...radead.org>
To: 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>,
	Eric Biederman <ebiederm@...ssion.com>,
	David Woodhouse <dwmw@...zon.co.uk>,
	Sourabh Jain <sourabhjain@...ux.ibm.com>,
	Hari Bathini <hbathini@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Baoquan He <bhe@...hat.com>,
	Yuntao Wang <ytcoode@...il.com>,
	David Kaplan <david.kaplan@....com>,
	Tao Liu <ltao@...hat.com>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Kai Huang <kai.huang@...el.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Breno Leitao <leitao@...ian.org>,
	Wei Yang <richard.weiyang@...il.com>,
	Rong Xu <xur@...gle.com>,
	Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
	linux-kernel@...r.kernel.org,
	kexec@...ts.infradead.org,
	Simon Horman <horms@...nel.org>,
	Dave Young <dyoung@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	bsz@...zon.de,
	nathan@...nel.org
Subject: [PATCH v2 0/9] x86/kexec: Fixes for tip/x86/boot

Fix a few bugs introduced by the recent rework of the relocate_kernel()
code, and one which has been there in the kjump code from the beginning.

 • Global read-only TLB entries made relocate_kernel() crash when writing
   to its own page after the %cr3 switch should have made it writeable.
 • The preserve_context flag was lost when invoking swap_pages on the way
   back, causing pages not to be swapped.
 • The wrong page was being used as the swap page.
 • The ABI for the kjump call asks the callee to put its entry address for
   next time at %rsp+8 before returning, but we set %rsp to the top of the
   available page, such that the entry address is at the start of some
   other page.
 • The relocate_kernel() function lacked Clang CFI information, but is now
   called via a function pointer, leading to a crash¹.
 • The relocate_kernel() code and data could end up being linked into the
   wrong place for a LTO / -ffunction-sections build.

Thanks to Nathan for reporting many of the above.

Also a few minor cleanups, including a comments-only patch from Rafael
on the suspend-like part of kjump as a prelude to actually cleaning that
up.

¹ Fixed by just adding __nocfi. Actually providing the CFI information
for relocate_kernel() will need a bit more work, so let's just do the
simple fix for now.

 v2:
 • Rebase
 • Save a whole byte on a 'movq $1, %r11' instruction.
 • Fix duplicated word in comment.
 • Avoid absolute relocations against __relocate_kernel_start

David Woodhouse (7):
      x86/kexec: Disable global pages before writing to control page
      x86/kexec: Ensure preserve_context flag is set on return to kernel
      x86/kexec: Use correct swap page in swap_pages function
      x86/kexec: Fix stack and handling of re-entry point for ::preserve_context
      x86/kexec: Mark machine_kexec() with __nocfi
      x86/kexec: Cope with relocate_kernel() not being at the start of the page
      x86/kexec: Use typedef for relocate_kernel_fn function prototype

Nathan Chancellor (1):
      x86/kexec: Fix location of relocate_kernel with -ffunction-sections

Rafael J. Wysocki (1):
      kexec_core: Add and update comments regarding the KEXEC_JUMP flow

 arch/x86/include/asm/kexec.h         | 26 ++++++++--------
 arch/x86/kernel/machine_kexec_32.c   |  7 +----
 arch/x86/kernel/machine_kexec_64.c   |  8 ++---
 arch/x86/kernel/relocate_kernel_64.S | 57 ++++++++++++++++++++++++------------
 arch/x86/kernel/vmlinux.lds.S        |  4 +--
 kernel/kexec_core.c                  | 23 +++++++++++----
 6 files changed, 74 insertions(+), 51 deletions(-)

Powered by blists - more mailing lists