From: Chen Huang chenhuang5@huawei.com
commit eac2f3059e02382d91f8c887462083841d6ea2a3 upstream.
As [1] and [2] said, the arch_stack_walk should not to trace itself, or it will leave the trace unexpectedly when called. The example is when we do "cat /sys/kernel/debug/page_owner", all pages' stack is the same.
arch_stack_walk+0x18/0x20 stack_trace_save+0x40/0x60 register_dummy_stack+0x24/0x5e init_page_owner+0x2e
So we use __builtin_frame_address(1) as the first frame to be walked. And mark the arch_stack_walk() noinline.
We found that pr_cont will affact pages' stack whose task state is RUNNING when testing "echo t > /proc/sysrq-trigger". So move the place of pr_cont and mark the function dump_backtrace() noinline.
Also we move the case when task == NULL into else branch, and test for it in "echo c > /proc/sysrq-trigger".
[1] https://lore.kernel.org/lkml/20210319184106.5688-1-mark.rutland@arm.com/ [2] https://lore.kernel.org/lkml/20210317142050.57712-1-chenjun102@huawei.com/
Signed-off-by: Chen Huang chenhuang5@huawei.com Fixes: 5d8544e2d007 ("RISC-V: Generic library routines and assembly") Cc: stable@vger.kernel.org Signed-off-by: Palmer Dabbelt palmerdabbelt@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/riscv/kernel/stacktrace.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-)
--- a/arch/riscv/kernel/stacktrace.c +++ b/arch/riscv/kernel/stacktrace.c @@ -27,10 +27,10 @@ void notrace walk_stackframe(struct task fp = frame_pointer(regs); sp = user_stack_pointer(regs); pc = instruction_pointer(regs); - } else if (task == NULL || task == current) { - fp = (unsigned long)__builtin_frame_address(0); - sp = sp_in_global; - pc = (unsigned long)walk_stackframe; + } else if (task == current) { + fp = (unsigned long)__builtin_frame_address(1); + sp = (unsigned long)__builtin_frame_address(0); + pc = (unsigned long)__builtin_return_address(0); } else { /* task blocked in __switch_to */ fp = task->thread.s[0]; @@ -106,15 +106,15 @@ static bool print_trace_address(void *ar return true; }
-void dump_backtrace(struct pt_regs *regs, struct task_struct *task, +noinline void dump_backtrace(struct pt_regs *regs, struct task_struct *task, const char *loglvl) { - pr_cont("%sCall Trace:\n", loglvl); walk_stackframe(task, regs, print_trace_address, (void *)loglvl); }
void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl) { + pr_cont("%sCall Trace:\n", loglvl); dump_backtrace(NULL, task, loglvl); }
@@ -139,7 +139,7 @@ unsigned long get_wchan(struct task_stru
#ifdef CONFIG_STACKTRACE
-void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie, +noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie, struct task_struct *task, struct pt_regs *regs) { walk_stackframe(task, regs, consume_entry, cookie);