[Android] Segmentation fault in libcoreclr.so

[yanzhenms]

Hi, after followed this tutorial https://github.com/qmfrederik/coredroid, I got a lot of binaries successfull. I pushed them to Android /data/local/tmp/ and try to run a HelloWorld sample. It doesn't show "Hello, world" but gives me a "segmentation fault in libcoreclr.so".

HWNXT:/data/local/tmp/hello1 $ ../dotnet/corerun  hello
WARNING: linker: /data/local/tmp/dotnet/libcoreclr.so: unused DT entry: type 0xf arg 0xeba
Segmentation fault

Are there pre-built binaries or docker for Android cross built so I can save some time?

Thanks~

[janvorli]

I am not aware of any prebuilt binaries availability. Have you tried to run it under lldb as the tutorial describes? That could give us some idea on what's wrong.

[yanzhenms]

I cannot build the master branch cause it keeps reporting "cannot find version.cpp" error, even if 'skipgenerateversion' argument is present, so I switch to release/2.2.

I can build v2.2 successfully, and run it under lldb, I got the following information:

(lldb) run /data/local/tmp/coredroid/helloworld.dll
Process 24591 launched: '/home/yanzhen/.lldb/module_cache/remote-android/.cache/AA3284A1-3274-0BBC-7BC2-628EB50E7CE1-4B6635AD/corerun' (aarch64)
(lldb) WARNING: linker: /data/local/tmp/coredroid/libcoreclr.so: unused DT entry: type 0xf arg 0xee1
Process 24591 stopped
* thread dotnet/coreclr#1, name = 'corerun', stop reason = signal SIGSEGV: address access protected (fault address: 0x7fb6ec2bd0)
    frame #0: 0x0000007fb7f5ba10 linker64`__dl__ZN6soinfo8relocateI20plain_reloc_iteratorEEbRK14VersionTrackerOT_RK10LinkedListIS_19SoinfoListAllocatorESB_ + 1144
linker64`__dl__ZN6soinfo8relocateI20plain_reloc_iteratorEEbRK14VersionTrackerOT_RK10LinkedListIS_19SoinfoListAllocatorESB_:
->  0x7fb7f5ba10 <+1144>: str    x8, [x19]
    0x7fb7f5ba14 <+1148>: ldp    x8, x28, [x23, #0x8]
    0x7fb7f5ba18 <+1152>: add    x21, x21, #0x1            ; =0x1 
    0x7fb7f5ba1c <+1156>: cmp    x28, x8
bt
* thread dotnet/coreclr#1, name = 'corerun', stop reason = signal SIGSEGV: address access protected (fault address: 0x7fb6ec2bd0)
  * frame #0: 0x0000007fb7f5ba10 linker64`__dl__ZN6soinfo8relocateI20plain_reloc_iteratorEEbRK14VersionTrackerOT_RK10LinkedListIS_19SoinfoListAllocatorESB_ + 1144
    frame dotnet/coreclr#1: 0x0000007fb7f5aa70 linker64`__dl__ZN6soinfo10link_imageERK10LinkedListIS_19SoinfoListAllocatorES4_PK17android_dlextinfo + 520
    frame dotnet/coreclr#2: 0x0000007fb7f5dfb4 linker64`__dl__ZL14find_librariesP19android_namespace_tP6soinfoPKPKcmPS2_PNSt3__16vectorIS2_NS8_9allocatorIS2_EEEEmiPK17android_dlextinfob + 3312
    frame dotnet/coreclr#3: 0x0000007fb7f575a8 linker64`__dl__Z9do_dlopenPKciPK17android_dlextinfoPv + 504
    frame dotnet/coreclr#4: 0x0000007fb7f5457c linker64`__dl_dlopen + 60
    frame dotnet/coreclr#5: corerun`ExecuteManagedAssembly(currentExeAbsolutePath=0x0000007fb782e018, clrFilesAbsolutePath=0x0000007fb782e098, managedAssemblyAbsolutePath=0x0000007fb782f018, managedAssemblyArgc=0, managedAssemblyArgv=0x0000000000000000) at coreruncommon.cpp:344
    frame dotnet/coreclr#6: corerun`corerun(argc=2, argv=0x0000007ffffffdc8) at corerun.cpp:149
    frame dotnet/coreclr#7: corerun`main(argc=2, argv=0x0000007ffffffdc8) at corerun.cpp:161
    frame dotnet/coreclr#8: 0x0000007fb7e16710 libc.so`__libc_init + 92
    frame dotnet/coreclr#9: 0x000000555555e374 corerun`do_arm64_start + 64
    frame dotnet/coreclr#10: 0x0000007fb7f53e7c linker64`__dl__start + 8

[janvorli]

It looks like there is a relocation in the libcoreclr.so and that is not allowed on Android. We used to have such an issue in the past, but at that time, the dynamic loader was not crashing with SIGSEGV, but rather showing "dlopen failed to open the libcoreclr.so with error dlopen failed: text relocations (DT_TEXTREL) found in 64-bit ELF file "/data/data/com.termux/files/usr/bin/Product/Linux.arm64.Debug/libcoreclr.so".
Since we use -fPIC option when building coreclr, my guess is that some newly added / modified assembler helper is responsible for that.

[janvorli]

@yanzhenms I am going to try it on my local Android device. I was actually able to build it from the master branch, the thing was to actually not to pass in the skipgenerateversion. This option seems to be broken for crossgen build now.
But I needed to update the cross/build-android-rootfs.sh due to the fact that libicu and liblzma package versions were updated.

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