[OpenWrt-Devel] [LEDE-DEV] [PATCH] include/kernel: Do not strip kernel's Elf

[Alexey Brodkin]

Hi Felix,

On Wed, 2016-05-18 at 15:49 +0200, Felix Fietkau wrote:
> On 2016-05-18 15:06, Alexey Brodkin wrote:
> > 
> > Hi Felix,
> > 
> > On Wed, 2016-05-18 at 14:57 +0200, Felix Fietkau wrote:
> > > 
> > > On 2016-05-16 16:42, Alexey Brodkin wrote:
> > > > 
> > > > 
> > > > If an image gets built as an Elf there's a chance
> > > > it will be used by developers for debugging purposes.
> > > > In that case it's very helpful to keep debugging info
> > > > in that image.
> > > > 
> > > > I would think that most OWRT-powered devices in production
> > > > will use some form of binary image for booting so Elf
> > > > flavours could be left a bit bulkier with more debug info
> > > > inside.
> > > > 
> > > > Signed-off-by: Alexey Brodkin <abrodkin at synopsys.com>
> > > You can get the bulky one directly from the kernel source directory, and
> > > there is definitely some value in having stripped ELF binaries as well
> > > for devices that can load them.
> > Well indeed in kernel's source directory we have an unstripped elf.
> > But what happens at least in case of ARC we build only one kernel's elf
> > and then as a post-built step we patch in .dtb for all boards we build OWRT.
> > 
> > In other words in "bin/arc770-uClibc" folder I have:
> >  1) openwrt-arc770-generic-axs101-initramfs.elf
> >  2) openwrt-arc770-generic-nsim_700-initramfs.elf
> > 
> > Both are stripped but work as they are on the corresponding boards.
> > 
> > In "build_dir/target-arc_arc700_uClibc-1.0.9/linux-arc770_generic/linux-4.4.7/"
> > I have perfectly unstripped vmlinux but it won't work on either board because of
> > missing device tree blob.
> > 
> > That means if one wants to get image for a board X with debug symbols he or she
> > will need to do manual patching in of .dtb. Which is not the most convenient thing ever.
> It's a lot simpler than that: You can boot the stripped and patched elf
> image from bin/ and use the vmlinux from the kernel source for the
> debugger afterwards. They are fully compatible.

Good point. So indeed if we do want stuff in "bin/" folder to be stripped
that seems to be the simplest approach.

But what if we with addition of another config option:
 a) toggle kernel's CONFIG_DEBUG_INFO
 b) use "--strip-unneeded" instead of currently used "-S" (which is an alias to "--strip-all").

-Alexey
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