On 03/06/2015 08:50 PM, Andy Lutomirski wrote:
I broke 32-bit kernels. The implementation of sp0 was correct as
far as I can tell, but sp0 was much weirder on x86_32 than I
realized. It has the following issues:
- Init's sp0 is inconsistent with everything else's: non-init tasks
are offset by 8 bytes. (I have no idea why, and the comment is unhelpful.)
- vm86 does crazy things to sp0.
Fix it up by replacing this_cpu_sp0() with current_top_of_stack()
and using a new percpu variable to track the top of the stack on
x86_32.
Fixes: 75182b1632a8 x86/asm/entry: Switch all C consumers of kernel_stack to
this_cpu_sp0()
Signed-off-by: Andy Lutomirski <l...@amacapital.net>
---
...
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index febc6aabc72e..759388c538cf 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -806,6 +806,8 @@ static int do_boot_cpu(int apicid, int cpu, struct
task_struct *idle)
#ifdef CONFIG_X86_32
/* Stack for startup_32 can be just as for start_secondary onwards */
irq_ctx_init(cpu);
+ per_cpu(cpu_current_top_of_stack, cpu) =
+ (unsigned long)task_stack_page(idle) + THREAD_SIZE;
#else
clear_tsk_thread_flag(idle, TIF_FORK);
initial_gs = per_cpu_offset(cpu);
Andy,
We need a similar change for Xen, otherwise 32-bit PV guests are not
happy. Is the patch above final (and then should I submit a separate
patch) or are you still working on it (and if so, please add the change
below)?
-boris
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 1c5e760..561d6f5 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -444,6 +444,8 @@ static int xen_cpu_up(unsigned int cpu, struct
task_struct *idle)
per_cpu(current_task, cpu) = idle;
#ifdef CONFIG_X86_32
irq_ctx_init(cpu);
+ per_cpu(cpu_current_top_of_stack, cpu) =
+ (unsigned long)task_stack_page(idle) + THREAD_SIZE;
#else
clear_tsk_thread_flag(idle, TIF_FORK);
#endif
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
