Date: Mon, 18 May 2015 17:29:50 -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: <CAGHfRMC10JJs7f9yzmNpeHNN8sM9ZFci1gpvqwqhvcGSQS4RXA@mail.gmail.com> In-Reply-To: <CAGHfRMAGTF0oh%2BR0kDxyx7PWSPfcTyZT-cMogF_LrV5pR2J4-w@mail.gmail.com> References: <554E41EE.2010202@ignoranthack.me> <554E4BD1.1030802@ignoranthack.me> <406EAA27-D825-408B-985E-DC3FFE746473@frob.org> <554E5263.8010205@ignoranthack.me> <20150509190347.10e1e2c2@kan> <CAGHfRMAGTF0oh%2BR0kDxyx7PWSPfcTyZT-cMogF_LrV5pR2J4-w@mail.gmail.com>
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On Mon, May 18, 2015 at 3:44 PM, NGie Cooper <yaneurabeya@gmail.com> wrote:
...
> 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
As a sidenote, this has been broken for over a decade:
https://svnweb.freebsd.org/base?view=revision&revision=127204 :(...
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