Re: [Crash-utility] arm64: "bt -f" output

> Dave, > > On Fri, Jun 10, 2016 at 04:37:42PM -0400, Dave Anderson wrote: > > Hi Takahiro, > > > > To address my concerns about your patch, I added a few additional changes and attached > > it to this email. The changes are: > > > > (1) Prevent the stack dump "below" the #0 level. Yes, the stack data region is contained within > > the incoming frame parameters, but it's ugly and we really don't care to see what's before > > the #0 crash_kexec and crash_save_cpu #0 frames. > > (2) Fill in the missing stack dump at the top of the process stack, up to, but not including > > the user-space exception frame. > > (3) Instead of showing the fp of 0 in the top-most frame's stack address, fill it in with the > > address of the user-space exception frame. > > > > Note that there is no dump of the stack containing the user-space exception frame, but the > > register dump itself should suffice. > > Well, the essential problem with my patch is that the output from "bt -f" > looks like: > #XX ['fp'] 'function' at 'pc' --- (1) > <function's stack dump> --- (2) > but that (1) and (2) are not printed as a single stack frame in the same > iteration of while loop in arm64_back_trace_cmd(). > (I hope you understand what I mean :) Actually I prefer your first approach. I find this new one confusing, not to mention unlike any of the other architectures in that the "frame level" #X address value is not contiguous with the stack addresses that get filled in by -f.

Taking your picture into account: stack grows to lower addresses. /|\ | | | new sp +------+ <--- |dyn | | | vars | | new fp +- - - + | |old fp| | a function's stack frame |old lr| | |static| | | vars| | old sp +------+ <--- |dyn | | vars | old fp +------+ | | Your first patch seemed natural to me because for any "#X" line containing a function name, that function's dynamic variables, the "old fp/old lr" pair, and the function's static variables were dumped below it (i.e., at higher stack addresses). > To be consistent with the out format of x86, the output should be > <function's stack dump> > #XX ['fp'] 'function' at 'pc' > > Unfortunately, this requires that arm64_back_trace_cmd() and other functions should be overhauled. > Please take a look at my next patch though it is uncompleted and still has room for improvement. I don't know what you mean by "consistent with the out format of x86"? With x86_64, each #<level> line is simply the stack address where the function pushed its return address as a result of its making a "callq" to the next function. Any local variables of the calling function would be at the next higher stack addresses: ... #X [stack address] function2 at 'return address' <function2's local variables> #Y [stack address] function1 at 'return address' <functions1's local variables> ... So for digging out local stack variables associated with a function, it's a simple matter of looking "below" it in the "bt -f" output.

Dave > Thanks, > -Takahiro AKASHI > > > > If you can live with the display, I'll clean up the patch, and maybe add > > the stack-layout diagram > > from your last post into a comment. It was quite helpful, especially in > > comparison to the > > x86_64 model, which is what I was mistakenly using as a guide. > > > > Thanks, > > Dave > > > > > > > > > diff --git a/arm64.c b/arm64.c > > index 86ec348..3b29ef4 100644 > > --- a/arm64.c > > +++ b/arm64.c > > @@ -1407,13 +1407,14 @@ arm64_print_stackframe_entry(struct bt_info *bt, > > int level, struct arm64_stackfr > > value_to_symstr(frame->pc, buf, > > bt->radix); > > } > > > > - if (bt->flags & BT_FULL) { > > - arm64_display_full_frame(bt, frame->sp); > > - bt->frameptr = frame->sp; > > + if ((bt->flags & BT_FULL) && level) { > > + arm64_display_full_frame(bt, frame->fp); > > + bt->frameptr = frame->fp; > > } > > > > fprintf(ofp, "%s#%d [%8lx] %s at %lx", level < 10 ? " " : "", > > level, > > - frame->sp, name_plus_offset ? name_plus_offset : name, > > frame->pc); > > +// frame->fp, name_plus_offset ? name_plus_offset : name, > > frame->pc); > > + frame->fp ? frame->fp : bt->stacktop - USER_EFRAME_OFFSET, > > name_plus_offset ? name_plus_offset : name, frame->pc); > > > > if (BT_REFERENCE_CHECK(bt)) > > arm64_do_bt_reference_check(bt, frame->pc, name); > > @@ -1447,8 +1448,12 @@ arm64_display_full_frame(struct bt_info *bt, ulong > > sp) > > if (bt->frameptr == sp) > > return; > > > > - if (!INSTACK(sp, bt) || !INSTACK(bt->frameptr, bt)) > > - return; > > + if (!INSTACK(sp, bt) || !INSTACK(bt->frameptr, bt)) { > > + if (sp == 0) > > + sp = bt->stacktop - USER_EFRAME_OFFSET; > > + else > > + return; > > + } > > > > words = (sp - bt->frameptr) / sizeof(ulong); > > > > @@ -1471,12 +1476,10 @@ arm64_unwind_frame(struct bt_info *bt, struct > > arm64_stackframe *frame) > > { > > unsigned long high, low, fp; > > unsigned long stack_mask; > > - unsigned long irq_stack_ptr, orig_sp, sp_in; > > + unsigned long irq_stack_ptr, orig_sp; > > struct arm64_pt_regs *ptregs; > > struct machine_specific *ms; > > > > - sp_in = frame->sp; > > - > > stack_mask = (unsigned long)(ARM64_STACK_SIZE) - 1; > > fp = frame->fp; > > > > @@ -1513,7 +1516,7 @@ arm64_unwind_frame(struct bt_info *bt, struct > > arm64_stackframe *frame) > > ptregs = (struct arm64_pt_regs > > *)&bt->stackbuf[(ulong)(STACK_OFFSET_TYPE(orig_sp))]; > > frame->sp = orig_sp; > > frame->pc = ptregs->pc; > > - bt->bptr = sp_in; > > + bt->bptr = fp; > > if (CRASHDEBUG(1)) > > error(INFO, > > "arm64_unwind_frame: switch stacks: fp: %lx sp: %lx pc: %lx\n", > > @@ -1904,8 +1907,10 @@ arm64_print_exception_frame(struct bt_info *bt, > > ulong pt_regs, int mode, FILE *o > > ulong LR, SP, offset; > > char buf[BUFSIZE]; > > > > +#if 0 /* FIXME? */ > > if (bt->flags & BT_FULL) > > arm64_display_full_frame(bt, pt_regs); > > +#endif > > > > if (CRASHDEBUG(1)) > > fprintf(ofp, "pt_regs: %lx\n", pt_regs); > > > -- > > Crash-utility mailing list > > Crash-utility(a)redhat.com > > https://www.redhat.com/mailman/listinfo/crash-utility > > -- > Crash-utility mailing list > Crash-utility(a)redhat.com > https://www.redhat.com/mailman/listinfo/crash-utility > -- Crash-utility mailing list Crash-utility(a)redhat.com https://www.redhat.com/mailman/listinfo/crash-utility