Re: [PATCH 2/2] riscv: stacktrace: Make walk_stackframe cross pt_regs frame

Guo Ren
2022-12-06T03:31:26Z

On Tue, Dec 6, 2022 at 10:59 AM Palmer Dabbelt <palmer@dabbelt.com> wrote:
>
> On Tue, 08 Nov 2022 22:49:37 PST (-0800), guoren@kernel.org wrote:
> > From: Guo Ren <guoren@linux.alibaba.com>
> >
> > The current walk_stackframe with FRAME_POINTER would stop unwinding at
> > ret_from_exception:
> > BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1518
> > in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 1, name: init
> > CPU: 0 PID: 1 Comm: init Not tainted 5.10.113-00021-g15c15974895c-dirty #192
> > Call Trace:
> > [<ffffffe0002038c8>] walk_stackframe+0x0/0xee
> > [<ffffffe000aecf48>] show_stack+0x32/0x4a
> > [<ffffffe000af1618>] dump_stack_lvl+0x72/0x8e
> > [<ffffffe000af1648>] dump_stack+0x14/0x1c
> > [<ffffffe000239ad2>] ___might_sleep+0x12e/0x138
> > [<ffffffe000239aec>] __might_sleep+0x10/0x18
> > [<ffffffe000afe3fe>] down_read+0x22/0xa4
> > [<ffffffe000207588>] do_page_fault+0xb0/0x2fe
> > [<ffffffe000201b80>] ret_from_exception+0x0/0xc
> >
> > The optimization would help walk_stackframe cross the pt_regs frame and
> > get more backtrace of debug info:
> > BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1518
> > in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 1, name: init
> > CPU: 0 PID: 1 Comm: init Not tainted 5.10.113-00021-g15c15974895c-dirty #192
> > Call Trace:
> > [<ffffffe0002038c8>] walk_stackframe+0x0/0xee
> > [<ffffffe000aecf48>] show_stack+0x32/0x4a
> > [<ffffffe000af1618>] dump_stack_lvl+0x72/0x8e
> > [<ffffffe000af1648>] dump_stack+0x14/0x1c
> > [<ffffffe000239ad2>] ___might_sleep+0x12e/0x138
> > [<ffffffe000239aec>] __might_sleep+0x10/0x18
> > [<ffffffe000afe3fe>] down_read+0x22/0xa4
> > [<ffffffe000207588>] do_page_fault+0xb0/0x2fe
> > [<ffffffe000201b80>] ret_from_exception+0x0/0xc
> > [<ffffffe000613c06>] riscv_intc_irq+0x1a/0x72
> > [<ffffffe000201b80>] ret_from_exception+0x0/0xc
> > [<ffffffe00033f44a>] vma_link+0x54/0x160
> > [<ffffffe000341d7a>] mmap_region+0x2cc/0x4d0
> > [<ffffffe000342256>] do_mmap+0x2d8/0x3ac
> > [<ffffffe000326318>] vm_mmap_pgoff+0x70/0xb8
> > [<ffffffe00032638a>] vm_mmap+0x2a/0x36
> > [<ffffffe0003cfdde>] elf_map+0x72/0x84
> > [<ffffffe0003d05f8>] load_elf_binary+0x69a/0xec8
> > [<ffffffe000376240>] bprm_execve+0x246/0x53a
> > [<ffffffe00037786c>] kernel_execve+0xe8/0x124
> > [<ffffffe000aecdf2>] run_init_process+0xfa/0x10c
> > [<ffffffe000aece16>] try_to_run_init_process+0x12/0x3c
> > [<ffffffe000afa920>] kernel_init+0xb4/0xf8
> > [<ffffffe000201b80>] ret_from_exception+0x0/0xc
> >
> > Here is the error injection test code for the above output:
> > drivers/irqchip/irq-riscv-intc.c:
> > static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
> > {
> > unsigned long cause = regs->cause & ~CAUSE_IRQ_FLAG;
> > + u32 tmp; __get_user(tmp, (u32 *)0);
> >
> > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > Signed-off-by: Guo Ren <guoren@kernel.org>
> > Cc: Palmer Dabbelt <palmer@rivosinc.com>
> > Cc: Changbin Du <changbin.du@intel.com>
> > ---
> > arch/riscv/kernel/entry.S | 2 +-
> > arch/riscv/kernel/stacktrace.c | 9 +++++++++
> > 2 files changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> > index b9eda3fcbd6d..329cf51fcd4d 100644
> > --- a/arch/riscv/kernel/entry.S
> > +++ b/arch/riscv/kernel/entry.S
> > @@ -248,7 +248,7 @@ ret_from_syscall_rejected:
> > andi t0, t0, _TIF_SYSCALL_WORK
> > bnez t0, handle_syscall_trace_exit
> >
> > -ret_from_exception:
> > +ENTRY(ret_from_exception)
>
> This at least needs an END(), but it should also be converted over to
Yes, I missed END() here.

> some non-function entry flavor. I converted it over to
> SYM_CODE_START_NOALIGN(), with the cooresponding SYM_CODE_END(), and put
> it on for-next.
Is that also for ret_from_fork & __switch_to?

>
> > REG_L s0, PT_STATUS(sp)
> > csrc CSR_STATUS, SR_IE
> > #ifdef CONFIG_TRACE_IRQFLAGS
> > diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
> > index bcfe9eb55f80..75c8dd64fc48 100644
> > --- a/arch/riscv/kernel/stacktrace.c
> > +++ b/arch/riscv/kernel/stacktrace.c
> > @@ -16,6 +16,8 @@
> >
> > #ifdef CONFIG_FRAME_POINTER
> >
> > +extern asmlinkage void ret_from_exception(void);
> > +
> > void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
> > bool (*fn)(void *, unsigned long), void *arg)
> > {
> > @@ -59,6 +61,13 @@ void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
> > fp = frame->fp;
> > pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
> > &frame->ra);
> > + if (pc == (unsigned long)ret_from_exception) {
> > + if (unlikely(!__kernel_text_address(pc) || !fn(arg, pc)))
> > + break;
> > +
> > + pc = ((struct pt_regs *)sp)->epc;
> > + fp = ((struct pt_regs *)sp)->s0;
> > + }
> > }
> >
> > }

--
Best Regards
Guo Ren