Recent change to struct pt_regs handling in entry.S, among other things,
changed how callee-preserved registers are saved around call
to lockdep_sys_exit_thunk:
# define LOCKDEP_SYS_EXIT_IRQ \
TRACE_IRQS_ON; \
sti; \
SAVE_EXTRA_REGS; \ <======= HERE
LOCKDEP_SYS_EXIT; \
RESTORE_EXTRA_REGS; \ <======= HERE
The change is in fact a bit fragile:
now we assume that LOCKDEP_SYS_EXIT_IRQ macro is used only
when there is a struct pt_regs on the stack.
So far this assumption is true, but it is probably a coincidence.
We can revert back to pushing registers, but this callee-preserved registers
saving appears bogus. It is not necessary: they _are_ callee-preserved,
and lockdep_sys_exit() does not touch them on the stack either.
First two patches clean up #define maze so that we can see
that LOCKDEP_SYS_EXIT macro call above is merely "call lockdep_sys_exit_thunk".
Last patch removes SAVE/RESTORE.
I tested this patch series and everything seems to run fine
on a lockdep-enabled kernel with these lines removed.
Denys Vlasenko (3):
x86: move ARCH_LOCKDEP_SYS_EXIT[IRQ] defines closer to their users
x86: fold ARCH_LOCKDEP_SYS_EXIT defines into their users
x86: do not save callee-preserved registers around lockdep_sys_exit_thunk
arch/x86/include/asm/irqflags.h | 45 +++++++++++++++++------------------------
1 file changed, 19 insertions(+), 26 deletions(-)
CC: Linus Torvalds <torva...@linux-foundation.org>
CC: Steven Rostedt <rost...@goodmis.org>
CC: Ingo Molnar <mi...@kernel.org>
CC: Borislav Petkov <b...@alien8.de>
CC: "H. Peter Anvin" <h...@zytor.com>
CC: Andy Lutomirski <l...@amacapital.net>
CC: Oleg Nesterov <o...@redhat.com>
CC: Frederic Weisbecker <fweis...@gmail.com>
CC: Alexei Starovoitov <a...@plumgrid.com>
CC: Will Drewry <w...@chromium.org>
CC: Kees Cook <keesc...@chromium.org>
CC: x...@kernel.org
CC: linux-kernel@vger.kernel.org
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1.8.1.4
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