--- /dev/null
+From 230b3034793247f61e6a0b08c44cf415f6d92981 Mon Sep 17 00:00:00 2001
+From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
+Date: Sat, 15 Jun 2013 12:13:40 +1000
+Subject: powerpc: Fix missing/delayed calls to irq_work
+
+From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
+
+commit 230b3034793247f61e6a0b08c44cf415f6d92981 upstream.
+
+When replaying interrupts (as a result of the interrupt occurring
+while soft-disabled), in the case of the decrementer, we are exclusively
+testing for a pending timer target. However we also use decrementer
+interrupts to trigger the new "irq_work", which in this case would
+be missed.
+
+This change the logic to force a replay in both cases of a timer
+boundary reached and a decrementer interrupt having actually occurred
+while disabled. The former test is still useful to catch cases where
+a CPU having been hard-disabled for a long time completely misses the
+interrupt due to a decrementer rollover.
+
+Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
+Tested-by: Steven Rostedt <rostedt@goodmis.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ arch/powerpc/kernel/irq.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/arch/powerpc/kernel/irq.c
++++ b/arch/powerpc/kernel/irq.c
+@@ -162,7 +162,7 @@ notrace unsigned int __check_irq_replay(
+ * in case we also had a rollover while hard disabled
+ */
+ local_paca->irq_happened &= ~PACA_IRQ_DEC;
+- if (decrementer_check_overflow())
++ if ((happened & PACA_IRQ_DEC) || decrementer_check_overflow())
+ return 0x900;
+
+ /* Finally check if an external interrupt happened */
--- /dev/null
+From 0e37739b1c96d65e6433998454985de994383019 Mon Sep 17 00:00:00 2001
+From: Michael Ellerman <michael@ellerman.id.au>
+Date: Thu, 13 Jun 2013 21:04:56 +1000
+Subject: powerpc: Fix stack overflow crash in resume_kernel when ftracing
+
+From: Michael Ellerman <michael@ellerman.id.au>
+
+commit 0e37739b1c96d65e6433998454985de994383019 upstream.
+
+It's possible for us to crash when running with ftrace enabled, eg:
+
+ Bad kernel stack pointer bffffd12 at c00000000000a454
+ cpu 0x3: Vector: 300 (Data Access) at [c00000000ffe3d40]
+ pc: c00000000000a454: resume_kernel+0x34/0x60
+ lr: c00000000000335c: performance_monitor_common+0x15c/0x180
+ sp: bffffd12
+ msr: 8000000000001032
+ dar: bffffd12
+ dsisr: 42000000
+
+If we look at current's stack (paca->__current->stack) we see it is
+equal to c0000002ecab0000. Our stack is 16K, and comparing to
+paca->kstack (c0000002ecab3e30) we can see that we have overflowed our
+kernel stack. This leads to us writing over our struct thread_info, and
+in this case we have corrupted thread_info->flags and set
+_TIF_EMULATE_STACK_STORE.
+
+Dumping the stack we see:
+
+ 3:mon> t c0000002ecab0000
+ [c0000002ecab0000] c00000000002131c .performance_monitor_exception+0x5c/0x70
+ [c0000002ecab0080] c00000000000335c performance_monitor_common+0x15c/0x180
+ --- Exception: f01 (Performance Monitor) at c0000000000fb2ec .trace_hardirqs_off+0x1c/0x30
+ [c0000002ecab0370] c00000000016fdb0 .trace_graph_entry+0xb0/0x280 (unreliable)
+ [c0000002ecab0410] c00000000003d038 .prepare_ftrace_return+0x98/0x130
+ [c0000002ecab04b0] c00000000000a920 .ftrace_graph_caller+0x14/0x28
+ [c0000002ecab0520] c0000000000d6b58 .idle_cpu+0x18/0x90
+ [c0000002ecab05a0] c00000000000a934 .return_to_handler+0x0/0x34
+ [c0000002ecab0620] c00000000001e660 .timer_interrupt+0x160/0x300
+ [c0000002ecab06d0] c0000000000025dc decrementer_common+0x15c/0x180
+ --- Exception: 901 (Decrementer) at c0000000000104d4 .arch_local_irq_restore+0x74/0xa0
+ [c0000002ecab09c0] c0000000000fe044 .trace_hardirqs_on+0x14/0x30 (unreliable)
+ [c0000002ecab0fb0] c00000000016fe3c .trace_graph_entry+0x13c/0x280
+ [c0000002ecab1050] c00000000003d038 .prepare_ftrace_return+0x98/0x130
+ [c0000002ecab10f0] c00000000000a920 .ftrace_graph_caller+0x14/0x28
+ [c0000002ecab1160] c0000000000161f0 .__ppc64_runlatch_on+0x10/0x40
+ [c0000002ecab11d0] c00000000000a934 .return_to_handler+0x0/0x34
+ --- Exception: 901 (Decrementer) at c0000000000104d4 .arch_local_irq_restore+0x74/0xa0
+
+ ... and so on
+
+__ppc64_runlatch_on() is called from RUNLATCH_ON in the exception entry
+path. At that point the irq state is not consistent, ie. interrupts are
+hard disabled (by the exception entry), but the paca soft-enabled flag
+may be out of sync.
+
+This leads to the local_irq_restore() in trace_graph_entry() actually
+enabling interrupts, which we do not want. Because we have not yet
+reprogrammed the decrementer we immediately take another decrementer
+exception, and recurse.
+
+The fix is twofold. Firstly make sure we call DISABLE_INTS before
+calling RUNLATCH_ON. The badly named DISABLE_INTS actually reconciles
+the irq state in the paca with the hardware, making it safe again to
+call local_irq_save/restore().
+
+Although that should be sufficient to fix the bug, we also mark the
+runlatch routines as notrace. They are called very early in the
+exception entry and we are asking for trouble tracing them. They are
+also fairly uninteresting and tracing them just adds unnecessary
+overhead.
+
+[ This regression was introduced by fe1952fc0afb9a2e4c79f103c08aef5d13db1873
+ "powerpc: Rework runlatch code" by myself --BenH
+]
+
+Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
+Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ arch/powerpc/include/asm/exception-64s.h | 2 +-
+ arch/powerpc/kernel/process.c | 4 ++--
+ 2 files changed, 3 insertions(+), 3 deletions(-)
+
+--- a/arch/powerpc/include/asm/exception-64s.h
++++ b/arch/powerpc/include/asm/exception-64s.h
+@@ -320,7 +320,7 @@ label##_common: \
+ */
+ #define STD_EXCEPTION_COMMON_ASYNC(trap, label, hdlr) \
+ EXCEPTION_COMMON(trap, label, hdlr, ret_from_except_lite, \
+- FINISH_NAP;RUNLATCH_ON;DISABLE_INTS)
++ FINISH_NAP;DISABLE_INTS;RUNLATCH_ON)
+
+ /*
+ * When the idle code in power4_idle puts the CPU into NAP mode,
+--- a/arch/powerpc/kernel/process.c
++++ b/arch/powerpc/kernel/process.c
+@@ -1218,7 +1218,7 @@ EXPORT_SYMBOL(dump_stack);
+
+ #ifdef CONFIG_PPC64
+ /* Called with hard IRQs off */
+-void __ppc64_runlatch_on(void)
++void notrace __ppc64_runlatch_on(void)
+ {
+ struct thread_info *ti = current_thread_info();
+ unsigned long ctrl;
+@@ -1231,7 +1231,7 @@ void __ppc64_runlatch_on(void)
+ }
+
+ /* Called with hard IRQs off */
+-void __ppc64_runlatch_off(void)
++void notrace __ppc64_runlatch_off(void)
+ {
+ struct thread_info *ti = current_thread_info();
+ unsigned long ctrl;
projects / thirdparty / kernel / stable-queue.git / commitdiff
