Cross compiling to Android "pie executable" results in "LSB shared
object"
lazarus / 43-Android

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han · 2024-06-26 17:50

I have Fpcupdeluxe installed. I want to cross compile from Linux to
Android pie executable.

Compiling a Hello Word program to Linux using options  -k-pie -k-znow
-Cg  gives the following Linux executable:

file test2
test2: ELF 64-bit LSB pie executable, ARM aarch64, version 1 (SYSV),
dynamically linked, interpreter /lib/ld-linux-aarch64.so.1, with
debug_info, not stripped

Changing the platform to Android gives the following result:

ELF 64-bit LSB shared object, ARM aarch64, version 1 (SYSV),
dynamically linked, interpreter libdl.so,
BuildID[sha1]=9eab5a4e162e001f4892880a899c0843f5cea6eb, with
debug_info, not stripped

So a shared object instead of the pie executable.

With only option -Cg-,  I can get an Android executable but it is not
Pie, so it doesn't work for Android 5+. Note the option -Cg-.
test2: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV),
dynamically linked, interpreter libdl.so,
BuildID[sha1]=79cf6dff7bf31d286eaed661e4e9dc02dda7df79, with
debug_info, not stripped


How can I cross compile to an Android pie executable? Or is this
caused by a problem with the cross compiler?

Han

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han · 2024-06-26 21:05

I have also compiled to Android using LAMW_manager. Same result. The
result is still a shared object and not a pie executable.

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nobody.00 · 2024-06-28 01:50

Quote from: han on June 26, 2024, 07:50:56 pmI have Fpcupdeluxe
installed. I want to cross compile from Linux to Android pie
executable.

Compiling a Hello Word program to Linux using options  -k-pie -k-znow
-Cg  gives the following Linux executable:

file test2
test2: ELF 64-bit LSB pie executable, ARM aarch64, version 1 (SYSV),
dynamically linked, interpreter /lib/ld-linux-aarch64.so.1, with
debug_info, not stripped

Changing the platform to Android gives the following result:

ELF 64-bit LSB shared object, ARM aarch64, version 1 (SYSV),
dynamically linked, interpreter libdl.so,
BuildID[sha1]=9eab5a4e162e001f4892880a899c0843f5cea6eb, with
debug_info, not stripped

So a shared object instead of the pie executable.

With only option -Cg-,  I can get an Android executable but it is not
Pie, so it doesn't work for Android 5+. Note the option -Cg-.
test2: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV),
dynamically linked, interpreter libdl.so,
BuildID[sha1]=79cf6dff7bf31d286eaed661e4e9dc02dda7df79, with
debug_info, not stripped


How can I cross compile to an Android pie executable? Or is this
caused by a problem with the cross compiler?

Han
Compile first as -o file.o
After using ld passing pie options
I have tais problem recently , after i put a detailed command to help
you

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han · 2024-06-28 08:53

Thanks. I assume you suggest to use the produced  .o file but how is
unclear to me.

There are some hints here:
https://wiki.freepascal.org/hardening
This suggest to add {$linklib c} to the source code. The output is
still a LSB shared object. Puzzling.

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han · 2024-06-28 10:44

From the link below it seem that a pie executable can be reported as a
shared object. But both Lubuntu 22 and Debian 12 report my command-
line program as a shared object.

https://forum.lazarus.freepascal.org/index.php/topic,56842.30.html
https://forum.lazarus.freepascal.org/index.php/topic,39338.msg451236.h
tml#msg451236

I got a report that this command seems to makes the program executable
in Android:
patchelf --set-interpreter /system/bin/linker64  yourprogram

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han · 2024-06-28 15:05

At moment I understand that a shared object is the same as a pie
executable. So that is no longer a problem. However the interpreter
for Android is wrongly defined as libdl.so. It should be 
/system/bin/linker64 or  /system/bin/linker for 32 bit:

This is what is reported after entering in Linux: file yourprogram:
yourprogram: ELF 64-bit LSB shared object, ARM aarch64, version 1
(SYSV), dynamically linked, interpreter libdl.so,
BuildID[sha1]=8eeee3c498f7728fe5428122b4acb179362e7bc3, stripped

The interpreter can be corrected using the patchelf program as
follows:

patchelf --set-interpreter /system/bin/linker64 ./yourprogram

This results in:
yourprogram: ELF 64-bit LSB shared object, ARM aarch64, version 1
(SYSV), dynamically linked, interpreter /system/bin/linker64,
BuildID[sha1]=2bf966cbb671b53c38504d838ff2d4c6b4979095, stripped

The options -Cg -k-pie -k-znow are not required. Default for Android?

The outstanding question is now how to get the correct Android
interpreter without using patchelf.

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han · 2024-07-17 09:06

A fix was added to the Fpcupdeluxe code:

https://github.com/LongDirtyAnimAlf/fpcupdeluxe/issues/697#event-
13532554461