[FFmpeg-devel] [PATCH 1/3] configure: Force mingw's ld to keep the reloc section
michaelni at gmx.at
Wed Sep 23 01:43:22 CEST 2015
On Mon, Sep 21, 2015 at 12:41:36AM -0400, Alex Smith wrote:
> From: Alex Smith <alex.smith at warpsharp.info>
> Binutils will always strip the relocation information from executable
> files even if it needs it (dynamicbase/ASLR). We can work around this
> by using the pic-executable flag combined with setting the correct entry
> point since apparently ld forgets what that should be. This problem
> affects both 32 and 64-bit mingw-w64.
> We can combine the nxcompat/dynamicbase check because they were added to
> binutils at the same time.
> Signed-off-by: Alex Smith <alex.smith at warpsharp.info>
> configure | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
> diff --git a/configure b/configure
> index d2a25bb..d6ab35a 100755
> --- a/configure
> +++ b/configure
> @@ -4367,8 +4367,6 @@ case $target_os in
> enabled shared && ! enabled small && check_cmd $windres --version && enable gnu_windres
> - check_ldflags -Wl,--nxcompat
> - check_ldflags -Wl,--dynamicbase
> enabled x86_32 && check_ldflags -Wl,--large-address-aware
> @@ -4392,6 +4390,17 @@ case $target_os in
> enable dos_paths
> + check_ldflags -Wl,--nxcompat,--dynamicbase
> + # Lets work around some stupidity in binutils.
> + # ld will strip relocations from executables even though we need them
> + # for dynamicbase (ASLR). Using -pie does retain the reloc section
> + # however ld then forgets what the entry point should be (oops) so we
> + # have to manually (re)set it.
> + if enabled x86_32; then
> + add_ldexeflags -Wl,--pic-executable,-e,_mainCRTStartup
> + elif enabled x86_64; then
> + add_ldexeflags -Wl,--pic-executable,-e,mainCRTStartup
> + fi
this is ugly, but ASLR is important thus applied
i did not apply the nxcompat dynamicbase merge as its unrelated
PS: if this breaks some version of mingw then this should be reverted
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
If a bugfix only changes things apparently unrelated to the bug with no
further explanation, that is a good sign that the bugfix is wrong.
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