From 9bbd4c56b0b642f04396da378296e68096d5afca Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Thu, 3 Nov 2016 20:23:08 +0000 Subject: arm64: prep stack walkers for THREAD_INFO_IN_TASK 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 Tested-by: Laura Abbott Cc: AKASHI Takahiro Cc: Andy Lutomirski Cc: James Morse Cc: Will Deacon Signed-off-by: Catalin Marinas --- arch/arm64/kernel/process.c | 20 ++++++++++++++------ arch/arm64/kernel/stacktrace.c | 5 +++++ arch/arm64/kernel/traps.c | 5 +++++ 3 files changed, 24 insertions(+), 6 deletions(-) (limited to 'arch/arm64/kernel') diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 01753cd7d3f0..ec7b9c00effe 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -350,27 +350,35 @@ 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 d53f99d4c223..8a552a33c6ef 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -181,6 +181,9 @@ 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; @@ -202,6 +205,8 @@ 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) diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 7ac30bf943e9..4731133286b3 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -148,6 +148,9 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) if (!tsk) tsk = current; + if (!try_get_task_stack(tsk)) + return; + /* * Switching between stacks is valid when tracing current and in * non-preemptible context. @@ -213,6 +216,8 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) stack + sizeof(struct pt_regs)); } } + + put_task_stack(tsk); } void show_stack(struct task_struct *tsk, unsigned long *sp) -- cgit v1.2.3