Always use PIC on FreeBSD, just like on Linux

[valpackett]

This fixes errors like

[…]
/usr/bin/ld: error: can't create dynamic relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol: _D4core5cpuid6_ssse3yb in reado
nly segment; recompile object files with -fPIC                                                                               
>>> defined in runtime/objects-shared/core/cpuid.o
>>> referenced by cpuid.d                                                                                                    
>>>               runtime/objects-shared/core/cpuid.o:(_D4core5cpuid5ssse3FNaNbNdNiNeZb)                                     

/usr/bin/ld: error: can't create dynamic relocation R_AARCH64_LDST8_ABS_LO12_NC against symbol: _D4core5cpuid6_ssse3yb in read
only segment; recompile object files with -fPIC
>>> defined in runtime/objects-shared/core/cpuid.o
>>> referenced by cpuid.d
>>>               runtime/objects-shared/core/cpuid.o:(_D4core5cpuid5ssse3FNaNbNdNiNeZb)                                     
                                                                                                                             
/usr/bin/ld: error: can't create dynamic relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol: _D4core5cpuid6_sse41yb in reado
nly segment; recompile object files with -fPIC                                                                               
>>> defined in runtime/objects-shared/core/cpuid.o                                                                           
>>> referenced by cpuid.d
>>>               runtime/objects-shared/core/cpuid.o:(_D4core5cpuid5sse41FNaNbNdNiNeZb)                                     

/usr/bin/ld: error: can't create dynamic relocation R_AARCH64_LDST8_ABS_LO12_NC against symbol: _D4core5cpuid6_sse41yb in read
only segment; recompile object files with -fPIC
>>> defined in runtime/objects-shared/core/cpuid.o
>>> referenced by cpuid.d
>>>               runtime/objects-shared/core/cpuid.o:(_D4core5cpuid5sse41FNaNbNdNiNeZb)

and allows ASLR on HardenedBSD (/ "coming soon" ASR on upstream FreeBSD) to do its thing

[kinke]

This shouldn't happen when linking shared druntime. The D modules for shared libraries are/should be explicitly compiled with -relocation-model=pic: https://github.com/ldc-developers/ldc/blob/master/runtime/CMakeLists.txt#L596

[valpackett]

This was coming from the variants macro I think. (But adding -relocation-model=pic there resulted in complaining about this option used two times.)

[kinke]

But adding -relocation-model=pic there resulted in complaining about this option used two times

Used two times because it's added in build_runtime_variant() I referred to; the variants macro calls the former. That's why I'm saying you shouldn't have troubles when linking shared druntime with current master.

[valpackett]

hm. I actually ended up with these after screwing with the CMake files. The original errors are in curl

/usr/bin/ld: error: can't create dynamic relocation R_AARCH64_ADD_ABS_LO12_NC against symbol: _D6object__T7destroyTS3std3net4curl4SMTP4ImplZQBiFKQBeZ9__lambda3MFNaNbNiNeZv in readonly segment; recompile object files with -fPIC                         
>>> defined in runtime/objects-debug/etc/c/curl.o
>>> referenced by object.d:530 (/home/greg/src/github.com/ldc-developers/ldc/runtime/druntime/src/object.d:530)              
>>>               runtime/objects-debug/etc/c/curl.o:(_D6object__T7destroyTS3std3net4curl4SMTP4ImplZQBiFKQBeZv)

[kinke]

This is Phobos now, which should be compiled once as PIC too [without BUILD_SHARED_LIBS=OFF; added in build_runtime_variant() too]. What's the library failing to link?

[kinke]

Argh... list(APPEND ${phobos2_d_flags} ...) in line 566 should most likely be list(APPEND phobos2_d_flags ...).

[valpackett]

Yep looks like that helped

[kinke]

Thx for checking. So is defaulting to PIC for FreeBSD safe/needed already, or would that fix suffice for the moment?

[valpackett]

Not strictly needed all the time I guess, but many C/C++ programs need it for various reasons.

/usr/ports % rg "fPIC" | wc -l
917
/usr/ports % rg "CFLAGS.*fPIC" | wc -l
482