[FFmpeg-devel] [PATCH] libavcodec: Remove dynamic relocs from aarch64/h264idct_neon.S

[Manoj Gupta]

On Wed, Jan 2, 2019 at 2:33 PM Michael Niedermayer
<michael at niedermayer.cc> wrote:
>
> On Wed, Jan 02, 2019 at 10:12:33AM -0800, Manoj Gupta wrote:
> > On Mon, Dec 31, 2018 at 8:31 AM Michael Niedermayer
> > <michael at niedermayer.cc> wrote:
> > >
> > > On Fri, Dec 28, 2018 at 03:12:53PM -0800, Manoj Gupta wrote:
> > > > Hi All,
> > > >
> > > > I recently had a problem building ffmpeg for AArch64 where lld linker
> > > > complained about text relocations in readonly segment. The following
> > > > patch fixes the linker complains by referring to a local label instead
> > > > of function name.
> > > >
> > > > This is similar in nature as the following previous commits:
> > > > https://www.mail-archive.com/ffmpeg-cvslog@ffmpeg.org/msg34290.html
> > > > https://www.mail-archive.com/ffmpeg-cvslog@ffmpeg.org/msg34419.html
> > > >
> > > > Thanks,
> > > > Manoj
> > > >
> > > > Patch:
> > > >
> > > > libavcodec: Remove dynamic relocs from aarch64/h264idct_neon.S
> > > >
> > > > Some of the assembly functions e.g. ff_h264_idct_dc_add_neon
> > > > has code like:
> > > >         movrel          x14, X(ff_h264_idct_add_neon)
> > > >
> > > > Linker cannot resolve them fully at link time and emits dynamic
> > > > relocations.
> > > > Use explicit labels instead so that no dynamic relocations are
> > > > needed at all.
> > > >
> > > > This avoids lld complains about text relocations.
> > > >
> > > > For background, see https://crbug.com/917919
> > > >
> > > > Signed-off-by: Manoj Gupta <manojgupta at chromium.org>
> > > > ---
> > > >  libavcodec/aarch64/h264idct_neon.S | 20 ++++++++++++--------
> > > >  1 file changed, 12 insertions(+), 8 deletions(-)
> > >
> > > Has this been tested on all common aarch64 platforms ?
> > >
> > I have tested this on Chromium with clang+lld linker and Debian
> > aarch64 cross compiler gcc + bfd linker.
> > Please let me know if more testing is needed.
>
> it would be good to test on apple too
>

Thanks, tested on my macbook compiling to aarch64 and the build itself was fine.

Use the following configure (+ make) command, hopefully I did it the right way.

 ./configure --cc=$HOME/ffmpeg/my-clang --cxx=$HOME/ffmpeg/my-clang++
--prefix=$HOME/ffmpeg/ffmpeg_out --enable-cross-compile --arch=aarch64
--target-os=darwin
--sysroot=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS12.0.sdk
--sysinclude=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS12.0.sdk

my-clang and my-clang++ are wrapper scripts passing the iphone SDK
headers to clang.

$ cat my-clang
#! /bin/bash
clang -isysroot $(xcrun --sdk iphoneos --show-sdk-path) -arch arm64 "$@"

Thanks,
Manoj

> thx
>
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