* Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> Hi,
>
> Here's 3 patches which fix two Xen PV spinlock bugs, and makes 
> CONFIG_CC_STACKPROTECTOR work on both 32- and 64-bit.
>
> The spinlock bugs are both rare races:
> - lock can briefly hold the lock while interrupts are enabled, allowing an 
> ISR to deadlock
> - unlock doesn't enforce CPU memory ordering between the actual unlock write 
> and the check
> to see if there are any pending waiters, so it can end up deciding there's 
> nobody to
> kick on unlock, leaving another CPU hanging. It needs a full mb() to 
> guarantee the correct
> ordering.
>
> The stack-protector fix bites the bullet and does a full GDT setup 
> early so that we can load %gs for the stack-protector canary 
> segment on i386. This also removes the assumption that the 
> initial percpu %fs segment has a zero base.
>
> x86-64 still just needs the GS_BASE MSR written, but that now 
> happens using the same code as i386 rather than being special 
> cased.
>
> Thanks,
> J
>
> The following changes since commit e07cccf4046978df10f2e13fe2b99b2f9b3a65db:
> Linus Torvalds (1):
> Linux 2.6.31-rc9
>
> are available in the git repository at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git bugfix
>
> Jeremy Fitzhardinge (2):
> xen: make -fstack-protector work under Xen
> xen: only enable interrupts while actually blocking for spinlock
>
> Yang Xiaowei (1):
> xen: use stronger barrier after unlocking lock
>
> arch/x86/mm/Makefile | 4 ++
> arch/x86/xen/Makefile | 2 +
> arch/x86/xen/enlighten.c | 131 
> +++++++++++++++++++++++++++++++++++++++-------
> arch/x86/xen/smp.c | 1 +
> arch/x86/xen/spinlock.c | 28 ++++++----
> drivers/xen/Makefile | 3 +
> 6 files changed, 140 insertions(+), 29 deletions(-)
Pulled, thanks a lot Jeremy!
A few comments:
> +# Make sure __phys_addr has no stackprotector
> +nostackp := $(call cc-option, -fno-stack-protector)
> +CFLAGS_ioremap.o := $(nostackp)
> +
Sure we could move __phys_addr into its own file and thus avoid 
turning off stackprotector for the rest of ioremap.c?
> --- a/arch/x86/xen/Makefile
> +++ b/arch/x86/xen/Makefile
> @@ -8,6 +8,7 @@ endif
> # Make sure early boot has no stackprotector
> nostackp := $(call cc-option, -fno-stack-protector)
> CFLAGS_enlighten.o := $(nostackp)
> +CFLAGS_mmu.o := $(nostackp)
A similar argument could be made here - what proportion of mmu.c is 
affected?
Also, once the commits have hit upstream feel free bounce them to 
stable@xxxxxxxxxx - they dont have Cc: <stable@xxxxxxxxxx> tags for 
automatic back-merging requests. The fixes narrowly missed v2.6.31.
 Ingo
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