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If an executable has copy relocations for extern protected data, that can only work if the shared object containing the definition is built with assumptions (a) the compiler emits GOT-generating relocations (b) the linker produces R_*_GLOB_DAT instead of R_*_RELATIVE. Otherwise the shared object uses its own definition directly and the executable accesses a stale copy. Note: the GOT relocations defeat the purpose of protected visibility as an optimization, and it turns out this never worked perfectly. glibc 2.36 will warn on copy relocations on protected data. Let's produce a warning at link time, matching ld.lld which has been used on many aarch64 OSes. Note: x86 requires GNU_PROPERTY_NO_COPY_ON_PROTECTED to have the error. This is to largely due to GCC 5's "x86-64: Optimize access to globals in PIE with copy reloc" which started to use direct access relocations for external data symbols in -fpie mode. GCC's aarch64 port does not have the change. Nowadays with most builds switching to -fpie/-fpic, aarch64 mostly doesn't need to worry about copy relocations. So for aarch64 we simply don't check GNU_PROPERTY_NO_COPY_ON_PROTECTED.
3 lines
99 B
Makefile
3 lines
99 B
Makefile
.*: tmpdir/copy-reloc-exe.o: copy relocation against non-copyable protected symbol `global_a'
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