lkml.org 
[lkml]   [2020]   [Aug]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 3/4] ARM: backtrace-clang: give labels more descriptive names
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

\
 
 \ /
  Last update: 2020-08-11 00:32    [W:0.707 / U:0.832 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site