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

On Mon, 2016-06-13 at 11:30 -0400, Dave Anderson wrote: > > ----- Original Message ----- > > 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: > I've been confused by the address in []'s on arm64. Is this supposed to be the stack address where the return address is stored, or does it vary by arch?

On x86_64 (crash-7.1.4-1.el6_6): crash> bt | grep " vfs_read at " #5 [ffff89b6e510ff08] vfs_read at ffffffff811dea1c crash> rd ffff89b6e510ff08 ffff89b6e510ff08: ffffffff811dea1c ........

On arm64 (crash-7.1.5-1.el7.aarch64) this isn't the case: crash> bt | grep " vfs_read at " #7 [ffff80015b93fdb0] vfs_read at ffff800000236b0c crash> rd ffff80015b93fdb0 ffff80015b93fdb0: ffff80015c92e100 ...\....

> ... > #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 -- Crash-utility mailing list Crash-utility(a)redhat.com https://www.redhat.com/mailman/listinfo/crash-utility