Re: Problem in bt for ARM64

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And please note that THREAD_SIZE, hence IRQ_STACK_SIZE,
is no longer constant since v4.14 due to KASAN and VMAP_STACK.

-Takahiro AKASHI

On Fri, Oct 13, 2017 at 05:29:12PM +0900, AKASHI Takahiro wrote:
> Dave,
> 
> On Fri, Sep 22, 2017 at 03:06:00PM -0400, Dave Anderson wrote:
> > 
> > Jan,
> > 
> > I went back to creating a machdep->machspec->user_eframe_offset value
> > to be able to account for both the 4.7 and the upcoming 4.14 pt_regs
> > changes:
> > 
> >   https://github.com/crash-utility/crash/commit/c975008e61121ef8785622c3bc26964da8fe0deb
> >  
> > Again, though, note that "bt" does not work with 4.14.
> 
> Even with your latest changes in 7.2.0, "bt" still has some issues:
> a.register dump at exception frame doesn't have correct values
>   (due to added stackframe[] in pt_regs)
> b. tracing irq stack to process stack fails
>   (due to irq-stack implementation changes and VMAP_STACK)
> c."bt -o" seems to have been broken for a while
> 
> Attached is my tentative patch, which hopefully addresses (a) and (b).
> While it is still far from perfect, it may help give you a heads-up.
> 
> Thanks,
> -Takahiro AKASHI
> 
> ===8<===
> From 156ec115b2a436a0738908153d676f8eeed84cb1 Mon Sep 17 00:00:00 2001
> From: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
> Date: Thu, 12 Oct 2017 10:46:34 +0900
> Subject: [PATCH] arm64: backtrace for v4.14
> 
> ---
>  arm64.c | 172 ++++++++++++++++++++++++++++++++++++++++++++++++++--------------
>  1 file changed, 136 insertions(+), 36 deletions(-)
> 
> diff --git a/arm64.c b/arm64.c
> index 20c5d34..22c8556 100644
> --- a/arm64.c
> +++ b/arm64.c
> @@ -72,6 +72,7 @@ static void arm64_cmd_mach(void);
>  static void arm64_display_machine_stats(void);
>  static int arm64_get_smp_cpus(void);
>  static void arm64_clear_machdep_cache(void);
> +static int arm64_on_process_stack(struct bt_info *, ulong);
>  static int arm64_in_alternate_stack(int, ulong);
>  static int arm64_on_irq_stack(int, ulong);
>  static void arm64_set_irq_stack(struct bt_info *);
> @@ -1336,29 +1337,60 @@ arm64_irq_stack_init(void)
>  	req = &request;
>  	struct machine_specific *ms = machdep->machspec;
>  
> -	if (!symbol_exists("irq_stack") ||
> -	    !(sp = per_cpu_symbol_search("irq_stack")) ||
> -	    !get_symbol_type("irq_stack", NULL, req) ||
> -	    (req->typecode != TYPE_CODE_ARRAY) ||
> -	    (req->target_typecode != TYPE_CODE_INT))
> -		return;
> +	if (!(ms->irq_stacks = (ulong *)malloc((size_t)(kt->cpus
> +						* sizeof(ulong)))))
> +		error(FATAL, "cannot malloc irq_stack addresses\n");
>  
> -	if (CRASHDEBUG(1)) {
> -		fprintf(fp, "irq_stack: \n");
> -		fprintf(fp, "  type: %s\n", 
> -			(req->typecode == TYPE_CODE_ARRAY) ? "TYPE_CODE_ARRAY" : "other");
> -		fprintf(fp, "  target_typecode: %s\n", 
> -			req->target_typecode == TYPE_CODE_INT ? "TYPE_CODE_INT" : "other");
> -		fprintf(fp, "  target_length: %ld\n", req->target_length);
> -		fprintf(fp, "  length: %ld\n", req->length);
> -	}
> +	if (symbol_exists("irq_stack") &&
> +	    (sp = per_cpu_symbol_search("irq_stack")) &&
> +	    get_symbol_type("irq_stack", NULL, req)) {
> +		/* before v4.14 or CONFIG_VMAP_STACK disabled */
> +		if (CRASHDEBUG(1)) {
> +			fprintf(fp, "irq_stack: \n");
> +			fprintf(fp, "  type: %s\n",
> +				(req->typecode == TYPE_CODE_ARRAY) ?
> +						"TYPE_CODE_ARRAY" : "other");
> +			fprintf(fp, "  target_typecode: %s\n",
> +				req->target_typecode == TYPE_CODE_INT ?
> +						"TYPE_CODE_INT" : "other");
> +			fprintf(fp, "  target_length: %ld\n",
> +						req->target_length);
> +			fprintf(fp, "  length: %ld\n", req->length);
> +		}
>  
> -	ms->irq_stack_size = req->length;
> -	if (!(ms->irq_stacks = (ulong *)malloc((size_t)(kt->cpus * sizeof(ulong)))))
> -		error(FATAL, "cannot malloc irq_stack addresses\n");
> +		ms->irq_stack_size = req->length;
> +
> +		for (i = 0; i < kt->cpus; i++)
> +			ms->irq_stacks[i] = kt->__per_cpu_offset[i] + sp->value;
> +	} else if (symbol_exists("irq_stack_ptr") &&
> +		   (sp = per_cpu_symbol_search("irq_stack_ptr")) &&
> +		   get_symbol_type("irq_stack_ptr", NULL, req)) {
> +		/* v4.14 and later with CONFIG_VMAP_STACK enabled */
> +		if (CRASHDEBUG(1)) {
> +			fprintf(fp, "irq_stack_ptr: \n");
> +			fprintf(fp, "  type: %x, %s\n",
> +				(int)req->typecode,
> +				(req->typecode == TYPE_CODE_PTR) ?
> +						"TYPE_CODE_PTR" : "other");
> +			fprintf(fp, "  target_typecode: %x, %s\n",
> +				(int)req->target_typecode,
> +				req->target_typecode == TYPE_CODE_INT ?
> +						"TYPE_CODE_INT" : "other");
> +			fprintf(fp, "  target_length: %ld\n",
> +						req->target_length);
> +			fprintf(fp, "  length: %ld\n", req->length);
> +		}
> +
> +		ms->irq_stack_size = 16384;
> +
> +		for (i = 0; i < kt->cpus; i++) {
> +			ulong p;
>  
> -	for (i = 0; i < kt->cpus; i++)
> -		ms->irq_stacks[i] = kt->__per_cpu_offset[i] + sp->value;
> +			p = kt->__per_cpu_offset[i] + sp->value;
> +			readmem(p, KVADDR, &(ms->irq_stacks[i]), sizeof(ulong),
> +					"IRQ stack pointer", RETURN_ON_ERROR);
> +		}
> +	}
>  
>  	machdep->flags |= IRQ_STACKS;
>  }
> @@ -1750,11 +1782,20 @@ arm64_display_full_frame(struct bt_info *bt, ulong sp)
>  	if (bt->frameptr == sp)
>  		return;
>  
> -	if (!INSTACK(sp, bt) || !INSTACK(bt->frameptr, bt)) {
> -		if (sp == 0)
> -			sp = bt->stacktop - USER_EFRAME_OFFSET;
> -		else
> -			return;
> +	if (INSTACK(bt->frameptr, bt)) {
> +		if (INSTACK(sp, bt)) {
> +			/* normal case */;
> +		} else {
> +			if (sp == 0)
> +				/* interrupt in user mode */
> +				sp = bt->stacktop - USER_EFRAME_OFFSET;
> +			else
> +				/* interrupt in kernel mode */
> +				sp = bt->stacktop;
> +		}
> +	} else {
> +		error(WARNING, "full display ?\n");
> +		return;
>  	}
>  
>  	words = (sp - bt->frameptr) / sizeof(ulong);
> @@ -1873,6 +1914,25 @@ arm64_unwind_frame(struct bt_info *bt, struct arm64_stackframe *frame)
>  	 *  orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);   (pt_regs pointer on process stack)
>  	 */
>  	if (machdep->flags & IRQ_STACKS) {
> +		if (machdep->flags & UNW_4_14) {
> +			if ((bt->flags & BT_IRQSTACK) &&
> +			    !arm64_on_irq_stack(bt->tc->processor, frame->fp)) {
> +				if (arm64_on_process_stack(bt, frame->fp)) {
> +					arm64_set_process_stack(bt);
> +
> +					frame->sp = frame->fp - SIZE(pt_regs) + 16;
> +					/* for switch_stack */
> +					/* fp still points to irq stack */
> +					bt->bptr = fp;
> +					/* for display_full_frame */
> +					/* sp points to process stack */
> +					bt->frameptr = frame->sp;
> +				} else {
> +					/* irq -> user */
> +					return FALSE;
> +				}
> +			}
> +		} else { /* !UNW_4_14 */
>  		ms = machdep->machspec;
>  		irq_stack_ptr = ms->irq_stacks[bt->tc->processor] + ms->irq_stack_size - 16;
>  
> @@ -1896,6 +1956,7 @@ arm64_unwind_frame(struct bt_info *bt, struct arm64_stackframe *frame)
>  				return FALSE;
>  			}
>  		}
> +		} /* UNW_4_14 */
>  	}
>  
>  	return TRUE;
> @@ -2086,10 +2147,17 @@ arm64_unwind_frame_v2(struct bt_info *bt, struct arm64_stackframe *frame,
>  			 * We are on process stack. Just add a faked frame
>  			 */
>  
> -			if (!arm64_on_irq_stack(bt->tc->processor, ext_frame.fp))
> -				frame->sp = ext_frame.fp
> -					    - sizeof(struct arm64_pt_regs);
> -			else {
> +			if (!arm64_on_irq_stack(bt->tc->processor, ext_frame.fp)) {
> +				if (MEMBER_EXISTS("pt_regs", "stackframe")) {
> +					frame->sp = ext_frame.fp
> +						    - sizeof(struct arm64_pt_regs) - 16;
> +					frame->fp = ext_frame.fp;
> +				} else {
> +					frame->sp = ext_frame.fp
> +						    - sizeof(struct arm64_pt_regs);
> +					frame->fp = frame->sp;
> +				}
> +			} else {
>  				/*
>  				 * FIXME: very exceptional case
>  				 * We are already back on process stack, but
> @@ -2109,10 +2177,10 @@ arm64_unwind_frame_v2(struct bt_info *bt, struct arm64_stackframe *frame,
>  				 * Really ugly
>  				 */
>  				frame->sp = frame->fp + 0x20;
> +				frame->fp = frame->sp;
>  				fprintf(ofp, " (Next exception frame might be wrong)\n");
>  			}
>  
> -			frame->fp = frame->sp;
>  		} else {
>  			/* We are on IRQ stack */
>  
> @@ -2122,9 +2190,15 @@ arm64_unwind_frame_v2(struct bt_info *bt, struct arm64_stackframe *frame,
>  			if (ext_frame.fp != irq_stack_ptr) {
>  				/* (2) Just add a faked frame */
>  
> -				frame->sp = ext_frame.fp
> -					    - sizeof(struct arm64_pt_regs);
> -				frame->fp = frame->sp;
> +				if (MEMBER_EXISTS("pt_regs", "stackframe")) {
> +					frame->sp = ext_frame.fp
> +						    - sizeof(struct arm64_pt_regs);
> +					frame->fp = ext_frame.fp;
> +				} else {
> +					frame->sp = ext_frame.fp
> +						    - sizeof(struct arm64_pt_regs) - 16;
> +					frame->fp = frame->sp;
> +				}
>  			} else {
>  				/*
>  				 * (3)
> @@ -2304,11 +2378,19 @@ arm64_back_trace_cmd(struct bt_info *bt)
>  		if (arm64_in_exception_text(bt->instptr) && INSTACK(stackframe.fp, bt)) {
>  			if (!(bt->flags & BT_IRQSTACK) ||
>  			    (((stackframe.sp + SIZE(pt_regs)) < bt->stacktop)))
> -				exception_frame = stackframe.fp - SIZE(pt_regs);
> +			{
> +				if (MEMBER_EXISTS("pt_regs", "stackframe"))
> +					/* v4.14 or later */
> +					exception_frame = stackframe.fp
> +							  - SIZE(pt_regs) + 16;
> +				else
> +					exception_frame = stackframe.fp
> +							  - SIZE(pt_regs);
> +			}
>  		}
>  
>  		if ((bt->flags & BT_IRQSTACK) &&
> -		    !arm64_on_irq_stack(bt->tc->processor, stackframe.sp)) {
> +		    !arm64_on_irq_stack(bt->tc->processor, stackframe.fp)) {
>  			bt->flags &= ~BT_IRQSTACK;
>  			if (arm64_switch_stack(bt, &stackframe, ofp) == USER_MODE)
>  				break;
> @@ -2424,6 +2506,8 @@ user_space:
>  		 * otherwise show an exception frame.
>  		 * Since exception entry code doesn't have a real
>  		 * stackframe, we fake a dummy frame here.
> +		 * Note: Since we have a real stack frame in pt_regs,
> +		 * We no longer need a dummy frame on v4.14 or later.
>  		 */
>  		if (!arm64_in_exp_entry(stackframe.pc))
>  			continue;
> @@ -2669,7 +2753,9 @@ arm64_switch_stack(struct bt_info *bt, struct arm64_stackframe *frame, FILE *ofp
>  	if (frame->fp == 0)
>  		return USER_MODE;
>  
> -	arm64_print_exception_frame(bt, frame->sp, KERNEL_MODE, ofp);
> +	if (!(machdep->flags & UNW_4_14))
> +		arm64_print_exception_frame(bt, frame->sp, KERNEL_MODE, ofp);
> +
>  	return KERNEL_MODE;
>  }
>  
> @@ -3362,6 +3448,20 @@ arm64_clear_machdep_cache(void) {
>  	return;
>  }
>  
> +static int
> +arm64_on_process_stack(struct bt_info *bt, ulong stkptr)
> +{
> +	ulong stackbase, stacktop;
> +
> +	stackbase = GET_STACKBASE(bt->task);
> +	stacktop = GET_STACKTOP(bt->task);
> +
> +	if ((stkptr >= stackbase) && (stkptr < stacktop))
> +		return TRUE;
> +
> +	return FALSE;
> +}
> +
>  static int
>  arm64_on_irq_stack(int cpu, ulong stkptr)
>  {
> -- 
> 2.14.1
> 

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