Date: Mon, 18 May 2015 15:44:19 -0700 From: NGie Cooper <yaneurabeya@gmail.com> To: Alexander Kabaev <kabaev@gmail.com> Cc: Sean Bruno <sbruno@ignoranthack.me>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: How to get anything useful out of kgdb? Message-ID: <CAGHfRMAGTF0oh%2BR0kDxyx7PWSPfcTyZT-cMogF_LrV5pR2J4-w@mail.gmail.com> In-Reply-To: <20150509190347.10e1e2c2@kan> References: <554E41EE.2010202@ignoranthack.me> <554E4BD1.1030802@ignoranthack.me> <406EAA27-D825-408B-985E-DC3FFE746473@frob.org> <554E5263.8010205@ignoranthack.me> <20150509190347.10e1e2c2@kan>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sat, May 9, 2015 at 4:03 PM, Alexander Kabaev <kabaev@gmail.com> wrote:
> On Sat, 09 May 2015 11:30:59 -0700
> Sean Bruno <sbruno@ignoranthack.me> wrote:
>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA512
>>
>> On 05/09/15 11:09, Jeff Meegan wrote:
>> > You could try -O0, but also if you just care about txr, go up to
>> > frame 12 where txr initialized to the context arg to em_handle_tx()
>> > and print it out there.
>> >
>> > -j
>>
>> I'm guessing that the place to change -O2 -> -O0 is in kern.pre.mk ?
>>
>> sean
>
> No, it means you need to iescover DEBUG and how it affects optimization
> level :)
>
> .if defined(DEBUG)
> _MINUS_O= -O
> CTFFLAGS+= -g
> .else
> ...
>
> Say, I have 'makeoptions DEBUG="-g -gdwarf-2"' in my kernel config
> file. -gdwarf-2 is probably not required anymore.
This isn't working as advertised.
While trying to track down issues with clang at $work with variables
that were optimized out, I noticed that it was passing through -O2
explicitly, even though DEBUG=-g was defined in our KERNCONF, which is
supposed to set _MINUS_O to -O.
I did some more poking around and it appears to always be the case
with 11-CURRENT as well (see below).
I'll post a diff for kern.pre.mk that fixes this on Phabricator soon,
because this is breaking our debuggability of clang kernels.
Thanks,
-NGie
$ git diff sys/conf/kern.pre.mk
diff --git a/sys/conf/kern.pre.mk b/sys/conf/kern.pre.mk
index 8c3b9c6..2ab0647 100644
--- a/sys/conf/kern.pre.mk
+++ b/sys/conf/kern.pre.mk
@@ -102,6 +102,8 @@ CFLAGS.gcc+=${CFLAGS_ARCH_PARAMS}
.endif
WERROR?= -Werror
+.error "CFLAGS: ${CFLAGS}"
+
# XXX LOCORE means "don't declare C stuff" not "for locore.s".
ASM_CFLAGS= -x assembler-with-cpp -DLOCORE ${CFLAGS} ${ASM_CFLAGS.${.IMPSRC:T}}
$ script ts make buildkernel KERNCONF=GENERIC
KERNCONFDIR=/sys/amd64/conf/ SRCCONF=/dev/null __MAKE_CONF=/dev/null
-j12
Script started, output file is ts
--- buildkernel ---
--- buildkernel ---
--------------------------------------------------------------
>>> Kernel build for GENERIC started on Mon May 18 15:38:04 PDT 2015
--------------------------------------------------------------
===> GENERIC
mkdir -p /usr/obj/usr/src/sys
--------------------------------------------------------------
>>> stage 1: configuring the kernel
--------------------------------------------------------------
cd /usr/src/sys/amd64/conf;
PATH=/usr/obj/usr/src/tmp/legacy/usr/sbin:/usr/obj/usr/src/tmp/legacy/usr/bin:/usr/obj/usr/src/tmp/legacy/bin:/usr/obj/usr/src/tmp/usr/sbin:/usr/obj/usr/src/tmp/usr/bin:/sbin:/bin:/usr/sbin:/usr/bin
config -d /usr/obj/usr/src/sys/GENERIC -I '/sys/amd64/conf/'
'/sys/amd64/conf//GENERIC'
Kernel build directory is /usr/obj/usr/src/sys/GENERIC
Don't forget to do ``make cleandepend && make depend''
--------------------------------------------------------------
>>> stage 2.1: cleaning up the object tree
--------------------------------------------------------------
cd /usr/obj/usr/src/sys/GENERIC; MAKEOBJDIRPREFIX=/usr/obj
MACHINE_ARCH=amd64 MACHINE=amd64 CPUTYPE=
GROFF_BIN_PATH=/usr/obj/usr/src/tmp/legacy/usr/bin
GROFF_FONT_PATH=/usr/obj/usr/src/tmp/legacy/usr/share/groff_font
GROFF_TMAC_PATH=/usr/obj/usr/src/tmp/legacy/usr/share/tmac
_SHLIBDIRPREFIX=/usr/obj/usr/src/tmp _LDSCRIPTROOT= VERSION="FreeBSD
11.0-CURRENT amd64 1100073" INSTALL="sh /usr/src/tools/install.sh"
PATH=/usr/obj/usr/src/tmp/legacy/usr/sbin:/usr/obj/usr/src/tmp/legacy/usr/bin:/usr/obj/usr/src/tmp/legacy/bin:/usr/obj/usr/src/tmp/usr/sbin:/usr/obj/usr/src/tmp/usr/bin:/sbin:/bin:/usr/sbin:/usr/bin
CC="cc " CXX="c++ " DEPFLAGS="" CPP="cpp " AS="as" AR="ar" LD="ld"
NM=nm OBJDUMP=objdump OBJCOPY="objcopy" RANLIB=ranlib STRINGS=
SIZE="size" make -j 12 -J 15,16 -m /usr/src/share/mk KERNEL=kernel
cleandir
make[2]: "/usr/src/sys/conf/kern.pre.mk" line 105: "CFLAGS: -O2 -pipe
-fno-strict-aliasing -g -nostdinc -I. -I/usr/src/sys -D_KERNEL
-DHAVE_KERNEL_OPTION_HEADERS -include opt_global.h"
>From /usr/obj/usr/src/sys/GENERIC/Makefile:
1 KERN_IDENT=GENERIC
2 MACHINE=amd64
3 MACHINE_ARCH=amd64
4 WITH_CTF=1
5 DEBUG=-g
6 S=/usr/src/sys
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAGHfRMAGTF0oh%2BR0kDxyx7PWSPfcTyZT-cMogF_LrV5pR2J4-w>