Widevine AARCH64 support

[tmm1]

We have aarch64 version of libwidevinecdm.so available now, as detailed here: emilsvennesson/script.module.inputstreamhelper#530

However to use it is still a challenge. I will document the requirements in this issue.

1. libnspr4.so dependency

   not sure if this is new, but the libnspr4 package must be installed because libwidevinecdm.so depends on libnspr4.so

2. glibc patch for _dt_determine_tlsoffset

   this patch is required: https://github.com/LibreELEC/LibreELEC.tv/blob/master/packages/devel/glibc/patches/arm/glibc-tls-libwidevinecdm.so-since-4.10.2252.0-has-TLS-with.patch

   without it, there will be a SEGV when running dlopen(). note that RPIOS already includes this patch in their libc6==2.31-13+rpt2+rpi1+deb11u5 package

3. glibc patch for GLIBC_ABI_DT_RELR support (if using glibc >= 2.36)

   patch found here: https://github.com/LibreELEC/LibreELEC.tv/blob/master/packages/devel/glibc/patches/arm/glibc-HACK-Don-t-check-GLIBC_ABI_DT_RELR-support-for-Chrom.patch

   not currently required on ubuntu (using glibc 2.35) or debian/rpios (using glibc 2.31)

4. LSE atomic symbols present in .dynsym

   inside the .so file, there are references to two required symbols:

   $ readelf -Ws libwidevinecdm.so | grep -v GLIBC | grep -v WEAK | grep -v NOTYPE | grep UND
       25: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __aarch64_ldadd4_acq_rel
      132: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __aarch64_swp4_acq_rel
   

   it seems on chromeos they have modified glibc/gcc packages to provide these as dynamic symbols inside various libraries. on stock linux glibc systems, these are not present because they are only used as static/hidden methods provided by libgcc.a and embedded inside every library that uses them. we would expect that these definitions would be embedded inside the widevine.so, but instead they are undefined and expected to be provided by an external library

[CastagnaIT]

have you some ideas when will be available a stable build?

[tmm1]

I only know what was posted here: https://groups.google.com/a/chromium.org/g/chromium-os-dev/c/GdZ0mebutXw

[jakermx]

@CastagnaIT hi there, long time no see... hope you are doing great

[Nachtzuster]

FYI: aarch64 seems to have hit stable:
from: https://chromiumdash.appspot.com/serving-builds?deviceCategory=ChromeOS
I pulled the 110 build for trogdor/lazor https://dl.google.com/dl/edgedl/chromeos/recovery/chromeos_15278.64.0_trogdor_recovery_stable-channel_mp-v7.bin.zip

$ file ROOT-A/opt/google/chrome/WidevineCdm/_platform_specific/cros_arm64/libwidevinecdm.so 
ROOT-A/opt/google/chrome/WidevineCdm/_platform_specific/cros_arm64/libwidevinecdm.so: ELF 64-bit LSB shared object, ARM aarch64, version 1 (SYSV), dynamically linked, BuildID[sha1]=b71fd3342a03fdb140e1f7a757960df219d63625, stripped
$ ls -l ROOT-A/opt/google/chrome/WidevineCdm/_platform_specific/cros_arm64/libwidevinecdm.so 
-rw-r--r--. 1 root root 9490256 Feb 14 03:21 ROOT-A/opt/google/chrome/WidevineCdm/_platform_specific/cros_arm64/libwidevinecdm.so

[CastagnaIT]

I have add new Wiki page with references to PR/Issue
so i close