Re: [PATCH 02/16] kernel.bbclass: fix buildpath QA issue

[Mark Hatle <mark.hatle@windriver.com>]

On 3/22/16 7:21 AM, Bruce Ashfield wrote:
> 
> 
> On Tue, Mar 22, 2016 at 8:12 AM, Hongxu Jia <hongxu.jia@windriver.com
> <mailto:hongxu.jia@windriver.com>> wrote:
> 
>     Since CFLAGS CPPFLAGS CXXFLAGS has been unset, variable DEBUG_FLAGS could
>     not been passed to compiler, so we explicitly add DEBUG_FLAGS to CC to
>     replace build path with target path.
> 
> 
> Can you be more explicit here ? What is typically contained in DEBUG_FLAGS ? The
> kernel builds its own compiler line and flags, so anything you are setting from this
> environment, should not be leaking into the kernel build.
> 
> .. which leaves me wondering, what exactly is in DEBUG_FLAGS, and how is it
> actually fixing the QA issue ?

The specific debug flag in question is being added to remap the on-disk path to
the path we want the items to look like from a debugging point of view.

The typical format of DEBUG_FLAGS is something like:

DEBUG_FLAGS ?= "-g -feliminate-unused-debug-types"

This was recently updated to include the remapping:

 DEBUG_FLAGS ?= "-g -feliminate-unused-debug-types \
                 -fdebug-prefix-map=${WORKDIR}=/usr/src/debug \
                 -fdebug-prefix-map=${STAGING_DIR_NATIVE}= \
                 -fdebug-prefix-map=${STAGING_DIR_HOST}= \

The idea is the WORKDIR is replaced with '/usr/src/debug' inside of the binary
and any debug symbol references.  This makes it much easier for the system to
work with supplied debug sources/symbols.

I'm not sure you want to use DEBUG_FLAGS since anything can be put in there....

Application space code should always use the DEBUG_FLAGS, or I think it's likely
a bug.

The kernel though should probably define it's own flag(s).  Most likely you'll
want something simple like:

-fdebug-prefix-map=${WORKDIR}=/usr/src/debug

Then all of the internal references to WORKDIR will be replaced with
'/usr/src/debug' which cross gdb can 'map' or on-target will actually look in
that location.  (A corresponding '-dbg' package should be provided with the
matching compilation sources at the local specified.)

--Mark

> Bruce
>  
> 
> 
>     [YOCTO #7058]
> 
>     Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com
>     <mailto:hongxu.jia@windriver.com>>
>     ---
>      meta/classes/kernel.bbclass | 4 ++--
>      1 file changed, 2 insertions(+), 2 deletions(-)
> 
>     diff --git a/meta/classes/kernel.bbclass b/meta/classes/kernel.bbclass
>     index c3eab50..d357ccf 100644
>     --- a/meta/classes/kernel.bbclass
>     +++ b/meta/classes/kernel.bbclass
>     @@ -207,7 +207,7 @@ kernel_do_compile() {
>                     copy_initramfs
>                    
>     use_alternate_initrd=CONFIG_INITRAMFS_SOURCE=${B}/usr/${INITRAMFS_IMAGE}-${MACHINE}.cpio
>             fi
>     -       oe_runmake ${KERNEL_IMAGETYPE_FOR_MAKE} ${KERNEL_ALT_IMAGETYPE}
>     CC="${KERNEL_CC}" LD="${KERNEL_LD}" ${KERNEL_EXTRA_ARGS} $use_alternate_initrd
>     +       oe_runmake ${KERNEL_IMAGETYPE_FOR_MAKE} ${KERNEL_ALT_IMAGETYPE}
>     CC="${KERNEL_CC} ${DEBUG_FLAGS}" LD="${KERNEL_LD}" ${KERNEL_EXTRA_ARGS}
>     $use_alternate_initrd
>             if test "${KERNEL_IMAGETYPE_FOR_MAKE}.gz" = "${KERNEL_IMAGETYPE}"; then
>                     gzip -9c < "${KERNEL_IMAGETYPE_FOR_MAKE}" > "${KERNEL_OUTPUT}"
>             fi
>     @@ -216,7 +216,7 @@ kernel_do_compile() {
>      do_compile_kernelmodules() {
>             unset CFLAGS CPPFLAGS CXXFLAGS LDFLAGS MACHINE
>             if (grep -q -i -e '^CONFIG_MODULES=y$' ${B}/.config); then
>     -               oe_runmake -C ${B} ${PARALLEL_MAKE} modules
>     CC="${KERNEL_CC}" LD="${KERNEL_LD}" ${KERNEL_EXTRA_ARGS}
>     +               oe_runmake -C ${B} ${PARALLEL_MAKE} modules CC="${KERNEL_CC}
>     ${DEBUG_FLAGS}" LD="${KERNEL_LD}" ${KERNEL_EXTRA_ARGS}
> 
>                     # Module.symvers gets updated during the
>                     # building of the kernel modules. We need to
>     --
>     1.9.1
> 
>     --
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> 
> 
> 
> -- 
> "Thou shalt not follow the NULL pointer, for chaos and madness await thee at its
> end"