kbuild: lto: Merge module sections if and only if CONFIG_LTO_CLANG is enabled
Merge module sections only when using Clang LTO. With ld.bfd, merging sections does not appear to update the symbol tables for the module, e.g. 'readelf -s' shows the value that a symbol would have had, if sections were not merged. ld.lld does not show this problem. The stale symbol table breaks gdb's function disassembler, and presumably other things, e.g. gdb -batch -ex "file arch/x86/kvm/kvm.ko" -ex "disassemble kvm_init" reads the wrong bytes and dumps garbage. Fixes: dd277622 ("kbuild: lto: merge module sections") Cc: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by:Sean Christopherson <seanjc@google.com> Reviewed-by:
Sami Tolvanen <samitolvanen@google.com> Tested-by:
Sami Tolvanen <samitolvanen@google.com> Signed-off-by:
Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20210322234438.502582-1-seanjc@google.com
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