UPSTREAM: 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 <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 9bbd4c56b0b642f04396da378296e68096d5afca)
Change-Id: I3ca86d1284456eeabe862bec8271570cc7e4a720
Signed-off-by: Greg Hackmann <ghackmann@google.com>
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 20a6d90..5d6c9da 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -425,27 +425,35 @@
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 d53f99d..8a552a3 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -181,6 +181,9 @@
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 @@
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 5bd77f3..86a87ae 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -149,6 +149,9 @@
if (!tsk)
tsk = current;
+ if (!try_get_task_stack(tsk))
+ return;
+
/*
* Switching between stacks is valid when tracing current and in
* non-preemptible context.
@@ -214,6 +217,8 @@
stack + sizeof(struct pt_regs));
}
}
+
+ put_task_stack(tsk);
}
void show_stack(struct task_struct *tsk, unsigned long *sp)