From: Nick Desaulniers <ndesaulniers@google.com>
To: Nathan Huckleberry <nhuck15@gmail.com>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>,
Dmitry Safonov <0x7f454c46@gmail.com>,
Russell King <linux@armlinux.org.uk>,
LKML <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Miles Chen <miles.chen@mediatek.com>,
linux-mediatek@lists.infradead.org,
Matthias Brugger <matthias.bgg@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Nathan Huckleberry <nhuck@google.com>,
Lvqiang Huang <lvqiang.huang@unisoc.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 3/4] ARM: backtrace-clang: give labels more descriptive names
Date: Mon, 10 Aug 2020 15:32:32 -0700 [thread overview]
Message-ID: <CAKwvOdn+MGgYf8k9uAUT55vBL+ERTjv+jx+t8SD9HO98-h2c0w@mail.gmail.com> (raw)
In-Reply-To: <CAN=-RxstJBjJUcOf9iuAxEcxYUhJTdF9JhPVWwQuefnE+3s52w@mail.gmail.com>
On Thu, Aug 6, 2020 at 3:39 PM Nathan Huckleberry <nhuck15@gmail.com> wrote:
>
> The style cleanup looks great. I just have one extra thing that
> can probably be thrown into this patch.
>
> On Thu, Jul 30, 2020 at 3:51 PM Nick Desaulniers
> <ndesaulniers@google.com> wrote:
> >
> > Removes the 1004 label; it was neither a control flow target, nor an
> > instruction we expect to produce a fault.
> >
> > Gives the labels slightly more readable names. The `b` suffixes are
> > handy to disambiguate between labels of the same identifier when there's
> > more than one. Since these labels are unique, let's just give them
> > names.
> >
> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> > ---
> > arch/arm/lib/backtrace-clang.S | 22 ++++++++++------------
> > 1 file changed, 10 insertions(+), 12 deletions(-)
> >
> > diff --git a/arch/arm/lib/backtrace-clang.S b/arch/arm/lib/backtrace-clang.S
> > index 40eb2215eaf4..7dad2a6843a5 100644
> > --- a/arch/arm/lib/backtrace-clang.S
> > +++ b/arch/arm/lib/backtrace-clang.S
> > @@ -121,8 +121,8 @@ for_each_frame: tst frame, mask @ Check for address exceptions
> > * start. This value gets updated to be the function start later if it is
> > * possible.
> > */
> > -1001: ldr sv_pc, [frame, #4] @ get saved 'pc'
> > -1002: ldr sv_fp, [frame, #0] @ get saved fp
> > +load_pc: ldr sv_pc, [frame, #4] @ get saved 'pc'
> > +load_fp: ldr sv_fp, [frame, #0] @ get saved fp
> >
> > teq sv_fp, mask @ make sure next frame exists
> > beq no_frame
> > @@ -142,7 +142,7 @@ for_each_frame: tst frame, mask @ Check for address exceptions
> > * registers for the current function, but the stacktrace is still printed
> > * properly.
> > */
> > -1003: ldr sv_lr, [sv_fp, #4] @ get saved lr from next frame
> > +load_lr: ldr sv_lr, [sv_fp, #4] @ get saved lr from next frame
> >
> > tst sv_lr, #0 @ If there's no previous lr,
> > beq finished_setup @ we're done.
> > @@ -166,8 +166,7 @@ finished_setup:
> > /*
> > * Print the function (sv_pc) and where it was called from (sv_lr).
> > */
> > -1004: mov r0, sv_pc
> > -
> > + mov r0, sv_pc
> > mov r1, sv_lr
> > mov r2, frame
> > bic r1, r1, mask @ mask PC/LR for the mode
> > @@ -182,7 +181,7 @@ finished_setup:
> > * pointer the comparison will fail and no registers will print. Unwinding will
> > * continue as if there had been no registers stored in this frame.
> > */
> > -1005: ldr r1, [sv_pc, #0] @ if stmfd sp!, {..., fp, lr}
> > +load_stmfd: ldr r1, [sv_pc, #0] @ if stmfd sp!, {..., fp, lr}
> > ldr r3, .Lopcode @ instruction exists,
> > teq r3, r1, lsr #11
> > ldr r0, [frame] @ locals are stored in
> > @@ -201,7 +200,7 @@ finished_setup:
> > mov frame, sv_fp @ above the current frame
> > bhi for_each_frame
> >
> > -1006: adr r0, .Lbad
> > +bad_frame: adr r0, .Lbad
> > mov r1, loglvl
> > mov r2, frame
> > bl printk
> > @@ -216,11 +215,10 @@ bad_lr: mov sv_fp, #0
> > ENDPROC(c_backtrace)
> > .pushsection __ex_table,"a"
> > .align 3
> > - .long 1001b, 1006b
> > - .long 1002b, 1006b
> > - .long 1003b, 1006b
> > - .long 1004b, 1006b
> > - .long 1005b, 1006b
> > + .long load_pc, bad_frame
> > + .long load_fp, bad_frame
> > + .long load_lr, bad_frame
> > + .long load_stmfd, bad_frame
>
> Load_stmfd should get its own fixup
> handler since it should emit errors about a bad
> pc, not a bad frame pointer.
Yeah, I can add that. It's a little orthogonal though to this patch
that renames labels. I'd consider more so a pre-existing bug. Let me
add a patch to the series that gives it a new fixup handler, separate
from the label renaming, in a v2 of the series.
>
> > .long prev_call, bad_lr
> > .popsection
> >
> > --
> > 2.28.0.163.g6104cc2f0b6-goog
> >
--
Thanks,
~Nick Desaulniers
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next prev parent reply other threads:[~2020-08-10 22:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-30 20:51 [PATCH 0/4] CONFIG_UNWINDER_FRAME_POINTER fixes+cleanups Nick Desaulniers
2020-07-30 20:51 ` [PATCH 1/4] ARM: backtrace-clang: check for NULL lr Nick Desaulniers
2020-08-07 18:07 ` Nathan Huckleberry
2020-07-30 20:51 ` [PATCH 2/4] ARM: backtrace-clang: add fixup for lr dereference Nick Desaulniers
2020-08-06 22:38 ` Nathan Huckleberry
2020-08-10 22:33 ` Nick Desaulniers
2020-08-20 0:13 ` Nick Desaulniers
2020-07-30 20:51 ` [PATCH 3/4] ARM: backtrace-clang: give labels more descriptive names Nick Desaulniers
2020-08-06 22:39 ` Nathan Huckleberry
2020-08-10 22:32 ` Nick Desaulniers [this message]
2020-07-30 20:51 ` [PATCH 4/4] ARM: backtrace: use more descriptive labels Nick Desaulniers
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