Re: [Buildroot] [PATCH 2/2] package/dmalloc: disable stack-protector

["Yann E. MORIN" <yann.morin.1998@free.fr>]

Fabrice, All,

On 2022-06-10 23:05 +0200, Fabrice Fontaine spake thusly:
> Fix the following build failure with stack-protector:
> 
> /home/autobuild/autobuild/instance-1/output-1/per-package/dmalloc/host/bin/i686-buildroot-linux-gnu-ld -shared --whole-archive -soname libdmallocth.so -o libdmallocth.so.t libdmallocth.a
> /home/autobuild/autobuild/instance-1/output-1/per-package/dmalloc/host/bin/i686-buildroot-linux-gnu-ld: libdmallocth.a(append.o): in function `append_long':
> append.c:(.text+0x115): undefined reference to `__stack_chk_fail_local'
> 
> Fixes:
>  - http://autobuild.buildroot.org/results/f808885dcbbe4322631fa57f72af23009babcb26
> 
> Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
> ---
>  package/dmalloc/dmalloc.mk | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/package/dmalloc/dmalloc.mk b/package/dmalloc/dmalloc.mk
> index 81ac467277..f0a05412c1 100644
> --- a/package/dmalloc/dmalloc.mk
> +++ b/package/dmalloc/dmalloc.mk
> @@ -12,7 +12,11 @@ DMALLOC_LICENSE = ISC
>  DMALLOC_LICENSE_FILES = LICENSE.txt
>  
>  DMALLOC_INSTALL_STAGING = YES
> -DMALLOC_CFLAGS = $(TARGET_CFLAGS)
> +# dmalloc must be compiled with no stack protection as it builds its shared
> +# library from its static library through --whole-archive, so forcefully pass
> +# -fno-stack-protector to override what Buildroot may have in TARGET_CFLAGS if
> +# BR2_SSP_* support is enabled.
> +DMALLOC_CFLAGS = $(TARGET_CFLAGS) -fno-stack-protector

At the risk of more goofiness, but the reference build issue had me
notice that dmalloc uses ld to do the link phase, while it should really
call gcc.

Indeed, I think the issue really is that -lssp (or the like) is missing
in the link command.

We have some very old, legacy, unexpained code that been there since the
dawn of times, that tweaks dmalloc's configure to shoehorn the cross-ld:

    $(SED) 's/(ld -/($${LD-ld} -/' $(@D)/configure
    $(SED) 's/'\''ld -/"$${LD-ld}"'\'' -/' $(@D)/configure

This should be converted over to use gcc, which would then properly pull
in the libraries needed when SSP is on.

However, this is not going to be trivial -whole-archive is not known to
gcc, so it must be passed as -Wl,-whole-archive.

Furthermore, -Wl,-no-whole-archive must be pased after the static
libdmalloc.a library (as explaiend in the ld manpage).

So, thisis a bit of a bigger change, but I otherwise fdo not think that
disabling SSP is a good idea, especially for a library that deals with
allocating memory...

Regards,
Yann E. MORIN.

>  ifeq ($(BR2_STATIC_LIBS),y)
>  DMALLOC_CONF_OPTS += --disable-shlib
> -- 
> 2.35.1
> 
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