linux/arch
Andy Lutomirski f10750536f x86/entry/64: Fix irqflag tracing wrt context tracking
Paolo pointed out that enter_from_user_mode could be called
while irqflags were traced as though IRQs were on.

In principle, this could confuse lockdep.  It doesn't cause any
problems that I've seen in any configuration, but if I build
with CONFIG_DEBUG_LOCKDEP=y, enable a nohz_full CPU, and add
code like:

	if (irqs_disabled()) {
		spin_lock(&something);
		spin_unlock(&something);
	}

to the top of enter_from_user_mode, then lockdep will complain
without this fix.  It seems that lockdep's irqflags sanity
checks are too weak to detect this bug without forcing the
issue.

This patch adds one byte to normal kernels, and it's IMO a bit
ugly. I haven't spotted a better way to do this yet, though.
The issue is that we can't do TRACE_IRQS_OFF until after SWAPGS
(if needed), but we're also supposed to do it before calling C
code.

An alternative approach would be to call trace_hardirqs_off in
enter_from_user_mode.  That would be less code and would not
bloat normal kernels at all, but it would be harder to see how
the code worked.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/86237e362390dfa6fec12de4d75a238acb0ae787.1447361906.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-24 09:55:02 +01:00
..
alpha mm: mlock: add mlock flags to enable VM_LOCKONFAULT usage 2015-11-05 19:34:48 -08:00
arc ARC fixes for 4.4-rc1 2015-11-14 09:09:37 -08:00
arm USB fixes for 4.4-rc2 2015-11-22 13:15:05 -08:00
arm64 arm64 fixes: 2015-11-19 12:21:23 -08:00
avr32 dmaengine updates for 4.4-rc1 2015-11-10 10:05:17 -08:00
blackfin
c6x
cris cris: Drop reference to get_cmos_time() 2015-11-02 20:03:05 +01:00
frv kmap_atomic_to_page() has no users, remove it 2015-11-09 15:11:24 -08:00
h8300 h8300 update for v4.4 2015-11-12 15:26:39 -08:00
hexagon
ia64 Power management and ACPI updates for v4.4-rc1 2015-11-04 18:10:13 -08:00
m32r
m68k block: change ->make_request_fn() and users to return a queue cookie 2015-11-07 10:40:46 -07:00
metag Metag architecture changes for v4.4 2015-11-10 16:24:25 -08:00
microblaze kmap_atomic_to_page() has no users, remove it 2015-11-09 15:11:24 -08:00
mips MIPS: ath79: Add a machine entry for booting OF machines 2015-11-20 15:44:57 +01:00
mn10300
nios2 nios2 update for v4.4-rc1 2015-11-09 16:36:10 -08:00
openrisc
parisc Merge branch 'parisc-4.4-2' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux 2015-11-22 12:50:58 -08:00
powerpc powerpc: Wire up sys_mlock2() 2015-11-16 17:05:53 +11:00
s390 s390: remove SALIPL loader 2015-11-16 12:51:11 +01:00
score
sh Merge branch 'akpm' (patches from Andrew) 2015-11-07 14:32:45 -08:00
sparc sparc/sparc64: allocate sys_membarrier system call number 2015-11-09 15:11:24 -08:00
tile kmap_atomic_to_page() has no users, remove it 2015-11-09 15:11:24 -08:00
um um: Switch clocksource to hrtimers 2015-11-06 22:54:49 +01:00
unicore32 pwm: Changes for v4.4-rc1 2015-11-11 09:16:10 -08:00
x86 x86/entry/64: Fix irqflag tracing wrt context tracking 2015-11-24 09:55:02 +01:00
xtensa Merge branch 'for-4.4/io-poll' of git://git.kernel.dk/linux-block 2015-11-10 17:23:49 -08:00
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