From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Wed, 19 Oct 2016 20:10:29 +0100 Subject: [PATCH 05/10] arm64: prep stack walkers for THREAD_INFO_IN_TASK In-Reply-To: <1476904234-9511-1-git-send-email-mark.rutland@arm.com> References: <1476904234-9511-1-git-send-email-mark.rutland@arm.com> Message-ID: <1476904234-9511-6-git-send-email-mark.rutland@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org When CONFIG_THREAD_INFO_IN_TASK is selected, task stacks may be freed before a task is destroyed. To account for this, the stacks are refcounted, and when manipulating the stack of another task, it is necessary to get/put the stack to ensure it isn't freed and/or re-used while we do so. This patch reworks the arm64 stack walking code to account for this. When CONFIG_THREAD_INFO_IN_TASK is not selected these perform no refcounting, and this should only be a structural change that does not affect behaviour. Signed-off-by: Mark Rutland Cc: AKASHI Takahiro Cc: Andy Lutomirski Cc: Catalin Marinas Cc: James Morse Cc: Will Deacon --- arch/arm64/kernel/process.c | 20 ++++++++++++++------ arch/arm64/kernel/stacktrace.c | 5 +++++ 2 files changed, 19 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 27b2f13..2f39036 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -340,27 +340,35 @@ struct task_struct *__switch_to(struct task_struct *prev, unsigned long get_wchan(struct task_struct *p) { struct stackframe frame; - unsigned long stack_page; + unsigned long stack_page, ret = 0; int count = 0; if (!p || p == current || p->state == TASK_RUNNING) return 0; + stack_page = (unsigned long)try_get_task_stack(p); + if (!stack_page) + return 0; + frame.fp = thread_saved_fp(p); frame.sp = thread_saved_sp(p); frame.pc = thread_saved_pc(p); #ifdef CONFIG_FUNCTION_GRAPH_TRACER frame.graph = p->curr_ret_stack; #endif - stack_page = (unsigned long)task_stack_page(p); do { if (frame.sp < stack_page || frame.sp >= stack_page + THREAD_SIZE || unwind_frame(p, &frame)) - return 0; - if (!in_sched_functions(frame.pc)) - return frame.pc; + goto out; + if (!in_sched_functions(frame.pc)) { + ret = frame.pc; + goto out; + } } while (count ++ < 16); - return 0; + +out: + put_task_stack(p); + return ret; } unsigned long arch_align_stack(unsigned long sp) diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 5b80068..c77e5b6 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -182,6 +182,9 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) struct stack_trace_data data; struct stackframe frame; + if (!try_get_task_stack(tsk)) + return; + data.trace = trace; data.skip = trace->skip; @@ -203,6 +206,8 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) walk_stackframe(tsk, &frame, save_trace, &data); if (trace->nr_entries < trace->max_entries) trace->entries[trace->nr_entries++] = ULONG_MAX; + + put_task_stack(tsk); } void save_stack_trace(struct stack_trace *trace) -- 1.9.1