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(-)