[Buildroot] [PATCH RFC v1 1/1] gcc: improve checking of stack smashing support with uclibc

[Arnout Vandecappelle <arnout@mind.be>]

On 19-09-15 20:05, Brendan Heading wrote:
> Fixes:
> http://autobuild.buildroot.net/results/123/123a5b3f72ba8c1a4aa1cea5b7b846a04fd4e923/
> http://autobuild.buildroot.net/results/38c/38cfa4e7249a8770b06dbd392acba79303d3f9bc/
> 
> .. and others.
> 
> Improve GCC's checking of stack smashing support, adding a specific case
> statement for uclibc, and removing the check done after checking the
> glibc version.
> 
> Signed-off-by: Brendan Heading <brendanheading@gmail.com>
> ---
> Patch V1 - this initial version only fixes 4.7.4 - wanted to check that
> we are heading the right way before I fix all the other versions.
> 
> Note that I manually modified configure, rather than regenerating it from
> configure.ac.

 I think it would be a good idea to send this patch upstream in parallel to get
feedback from there as well. But then you should make it against 5.2.0 of course.


> Original plan was to reverse the order of the existing __GLIBC_MINOR__ and
> uclibc check. However, the uclibc check falls through if it does not
> detect uclibc, so I figure it better to add the separate case statement.

 IMHO it's better to leave this kind of comment in the commit log itself (i.e.
before the ---). Then there is an easy trace of it if someone, years down the
line, wonders why it was not done that way.

 Also, it would be possible to move the condition up by just splitting it:

 if __UCLIBC__; then
    if __UCLIBC_HAS_SSP__; then
       yes
    else
       no
  elif __GLIBC__ ...


> ---
>  ...ing-of-stack-smashing-support-with-uclibc.patch | 81 ++++++++++++++++++++++
>  1 file changed, 81 insertions(+)
>  create mode 100644 package/gcc/4.7.4/920-gcc-improve-checking-of-stack-smashing-support-with-uclibc.patch
> 
> diff --git a/package/gcc/4.7.4/920-gcc-improve-checking-of-stack-smashing-support-with-uclibc.patch b/package/gcc/4.7.4/920-gcc-improve-checking-of-stack-smashing-support-with-uclibc.patch
> new file mode 100644
> index 0000000..8f5d961
> --- /dev/null
> +++ b/package/gcc/4.7.4/920-gcc-improve-checking-of-stack-smashing-support-with-uclibc.patch
> @@ -0,0 +1,81 @@
> +From 39bbd72364c34da7ba78f26354512eb5229cebdc Mon Sep 17 00:00:00 2001
> +From: Brendan Heading <brendanheading@gmail.com>
> +Date: Fri, 18 Sep 2015 14:54:25 +0100
> +Subject: [PATCH 1/1] gcc: improve checking of stack smashing support with

 Please avoid the 1/1 bit, by adding -N to format-patch.

> + uclibc
> +
> +Signed-off-by: Brendan Heading <brendanheading@gmail.com>
> +---
> + gcc/configure    | 15 +++++++++------
> + gcc/configure.ac | 15 +++++++++------
> + 2 files changed, 18 insertions(+), 12 deletions(-)
> +
> +diff --git a/gcc/configure b/gcc/configure
> +index 63cba0a..d1ac2ea 100755
> +--- a/gcc/configure
> ++++ b/gcc/configure
> +@@ -26797,6 +26797,15 @@ else
> +        *-*-musl*)
> +          # All versions of musl provide stack protector
> + 	 gcc_cv_libc_provides_ssp=yes;;
> ++       *-*-uclibc*)

 Can we be sure that uclibc will always have this in the tuple? Well, _we_ can
be sure of course, but can upstream be sure?

> ++      if $EGREP '^[ 	]*#[ 	]*define[ 	]+__UCLIBC__[ 	]+1' \
> ++        $target_header_dir/features.h > /dev/null && \

 You didn't check the existence of features.h (like is done below).


 Regards,
 Arnout

> ++	     test -f $target_header_dir/bits/uClibc_config.h && \
> ++	     $EGREP '^[ 	]*#[ 	]*define[ 	]+__UCLIBC_HAS_SSP__[ 	]+1' \
> ++	     $target_header_dir/bits/uClibc_config.h > /dev/null; then
> ++	  gcc_cv_libc_provides_ssp=yes
> ++      fi
> ++      ;;
> +        *-*-linux* | *-*-kfreebsd*-gnu | *-*-knetbsd*-gnu)
> +       # glibc 2.4 and later provides __stack_chk_fail and
> +       # either __stack_chk_guard, or TLS access to stack guard canary.
> +@@ -26811,12 +26820,6 @@ else
> + 	     && $EGREP '^[ 	]*#[ 	]*define[ 	]+__GLIBC_MINOR__[ 	]+([1-9][0-9]|[4-9])' \
> + 	     $target_header_dir/features.h > /dev/null; then
> + 	  gcc_cv_libc_provides_ssp=yes
> +-	elif $EGREP '^[ 	]*#[ 	]*define[ 	]+__UCLIBC__[ 	]+1' \
> +-	     $target_header_dir/features.h > /dev/null && \
> +-	     test -f $target_header_dir/bits/uClibc_config.h && \
> +-	     $EGREP '^[ 	]*#[ 	]*define[ 	]+__UCLIBC_HAS_SSP__[ 	]+1' \
> +-	     $target_header_dir/bits/uClibc_config.h > /dev/null; then
> +-	  gcc_cv_libc_provides_ssp=yes
> + 	fi
> +       # all versions of Bionic support stack protector
> +       elif test -f $target_header_dir/sys/cdefs.h \
> +diff --git a/gcc/configure.ac b/gcc/configure.ac
> +index ea1c147..5954cc7 100644
> +--- a/gcc/configure.ac
> ++++ b/gcc/configure.ac
> +@@ -4672,6 +4672,15 @@ AC_CACHE_CHECK(__stack_chk_fail in target C library,
> +        *-*-musl*)
> +          # All versions of musl provide stack protector
> + 	 gcc_cv_libc_provides_ssp=yes;;
> ++       *-*-uclibc*)
> ++      if $EGREP '^[ 	]*#[ 	]*define[ 	]+__UCLIBC__[ 	]+1' \
> ++         $target_header_dir/features.h > /dev/null && \
> ++	 test -f $target_header_dir/bits/uClibc_config.h && \
> ++	 $EGREP '^[ 	]*#[ 	]*define[ 	]+__UCLIBC_HAS_SSP__[ 	]+1' \
> ++	 $target_header_dir/bits/uClibc_config.h > /dev/null; then
> ++        gcc_cv_libc_provides_ssp=yes
> ++      fi
> ++      ;;
> +        *-*-linux* | *-*-kfreebsd*-gnu | *-*-knetbsd*-gnu)
> +       [# glibc 2.4 and later provides __stack_chk_fail and
> +       # either __stack_chk_guard, or TLS access to stack guard canary.
> +@@ -4686,12 +4695,6 @@ AC_CACHE_CHECK(__stack_chk_fail in target C library,
> + 	     && $EGREP '^[ 	]*#[ 	]*define[ 	]+__GLIBC_MINOR__[ 	]+([1-9][0-9]|[4-9])' \
> + 	     $target_header_dir/features.h > /dev/null; then
> + 	  gcc_cv_libc_provides_ssp=yes
> +-	elif $EGREP '^[ 	]*#[ 	]*define[ 	]+__UCLIBC__[ 	]+1' \
> +-	     $target_header_dir/features.h > /dev/null && \
> +-	     test -f $target_header_dir/bits/uClibc_config.h && \
> +-	     $EGREP '^[ 	]*#[ 	]*define[ 	]+__UCLIBC_HAS_SSP__[ 	]+1' \
> +-	     $target_header_dir/bits/uClibc_config.h > /dev/null; then
> +-	  gcc_cv_libc_provides_ssp=yes
> + 	fi
> +       # all versions of Bionic support stack protector
> +       elif test -f $target_header_dir/sys/cdefs.h \
> +-- 
> +2.4.3
> +
> 


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
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