Re: [Buildroot] [PATCH 2/2] toolchain/helpers.mk: gdbinit: set auto-load-safe-path before sysroot

[Arnout Vandecappelle <arnout@mind.be>]

On 13/09/2021 09:29, Thomas De Schampheleire wrote:
> From: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
> 
> The gdbinit supplied by Buildroot does two things:
> A. specify the sysroot where gdb can find shared libraries
> B. mark the sysroot as a 'safe path' for its auto-load feature, to make sure
>    that pretty printers for libstdc++.so are added automatically (see commit
>    6fb3216a80c64c08375429d89497eaeec5622150)
> 
> When debugging a core file, and the gdbinit file is specified via '-x'
> rather than '-ix', then the order of these settings matters: If you first
> set the sysroot, then gdb will immediately start finding the shared
> libraries it needs for the core file, detect libstdc++ and its associated
> libstdc++-gdb.py file, then give a big warning about safe paths:
> 
>    warning: File ".../i686-buildroot-linux-gnu/sysroot/lib/libstdc++.so.6.0.24-gdb.py"
>            auto-loading has been declined by your `auto-load safe-path' set
>            to "$debugdir:$datadir/auto-load".
>    To enable execution of this file add
>            add-auto-load-safe-path .../i686-buildroot-linux-gnu/sysroot/lib/libstdc++.so.6.0.24-gdb.py
>    line to your configuration file "/home/me/.gdbinit".
>    To completely disable this security protection add
>            set auto-load safe-path /
>    line to your configuration file "/home/me/.gdbinit".
>    For more information about this security protection see the
>    "Auto-loading safe path" section in the GDB manual.  E.g., run from the shell:
>            info "(gdb)Auto-loading safe path"
> 
> and the pretty printing code is not loaded. This is because the second
> line from the gdbinit file was not yet parsed at this point.
> 
> By changing the order (first configuring the safe path, then setting the
> sysroot), this issue does not appear and everything is as expected.
> 
> Note that when '-ix' were used instead of '-x' to pass the gdbinit file to
> gdb, then the order would not matter, because the entire gdbinit file would
> be parsed before considering the core file.
> However, even though the Buildroot manual now suggests '-ix', users may not
> have noticed this change and continue to use '-x'.

  Whaa, excellent, not content with fixing a bug once, you fix it twice!

  Applied to master, thanks. :-)

  Regards,
  Arnout


> 
> Signed-off-by: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
> ---
>   toolchain/helpers.mk | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/toolchain/helpers.mk b/toolchain/helpers.mk
> index 1dfb52ac38..ef8e9a5f64 100644
> --- a/toolchain/helpers.mk
> +++ b/toolchain/helpers.mk
> @@ -481,8 +481,8 @@ check_toolchain_ssp = \
>   #
>   gen_gdbinit_file = \
>   	mkdir -p $(STAGING_DIR)/usr/share/buildroot/ ; \
> -	echo "set sysroot $(STAGING_DIR)" > $(STAGING_DIR)/usr/share/buildroot/gdbinit ; \
> -	echo "add-auto-load-safe-path $(STAGING_DIR)" >> $(STAGING_DIR)/usr/share/buildroot/gdbinit
> +	echo "add-auto-load-safe-path $(STAGING_DIR)" > $(STAGING_DIR)/usr/share/buildroot/gdbinit ; \
> +	echo "set sysroot $(STAGING_DIR)" >> $(STAGING_DIR)/usr/share/buildroot/gdbinit
>   
>   # Given a path, determine the relative prefix (../) needed to return to the
>   # root level. Note that the last component is treated as a file component; use a
> 
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