From mboxrd@z Thu Jan 1 00:00:00 1970 From: rabin@rab.in (Rabin Vincent) Date: Wed, 19 Jan 2011 22:01:15 +0530 Subject: [PATCH] ARM: disable preempt when unwinding another task's stack Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Since we don't want to expose the unwinder to a volatile stack, we should make sure that we don't get preempted while doing the unwinding. Signed-off-by: Rabin Vincent --- arch/arm/kernel/process.c | 15 +++++++++++---- arch/arm/kernel/stacktrace.c | 5 +++++ 2 files changed, 16 insertions(+), 4 deletions(-) diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 94bbedb..56f10e6 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -459,10 +459,13 @@ EXPORT_SYMBOL(kernel_thread); unsigned long get_wchan(struct task_struct *p) { struct stackframe frame; + unsigned long wchan = 0; int count = 0; if (!p || p == current || p->state == TASK_RUNNING) return 0; + preempt_disable(); + frame.fp = thread_saved_fp(p); frame.sp = thread_saved_sp(p); frame.lr = 0; /* recovered from the stack */ @@ -470,11 +473,15 @@ unsigned long get_wchan(struct task_struct *p) do { int ret = unwind_frame(&frame); if (ret < 0) - return 0; - if (!in_sched_functions(frame.pc)) - return frame.pc; + break; + if (!in_sched_functions(frame.pc)) { + wchan = frame.pc; + break; + } } while (count ++ < 16); - return 0; + + preempt_enable(); + return wchan; } unsigned long arch_randomize_brk(struct mm_struct *mm) diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c index 381d23a..c6c9d2d 100644 --- a/arch/arm/kernel/stacktrace.c +++ b/arch/arm/kernel/stacktrace.c @@ -102,6 +102,8 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) trace->entries[trace->nr_entries++] = ULONG_MAX; return; #else + preempt_disable(); + data.no_sched_functions = 1; frame.fp = thread_saved_fp(tsk); frame.sp = thread_saved_sp(tsk); @@ -121,6 +123,9 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) walk_stackframe(&frame, save_trace, &data); if (trace->nr_entries < trace->max_entries) trace->entries[trace->nr_entries++] = ULONG_MAX; + + if (tsk != current) + preempt_enable(); } void save_stack_trace(struct stack_trace *trace) -- 1.7.2.3