From: Sean Christopherson seanjc@google.com
commit 6a3193cdd5e5b96ac65f04ee42555c216da332af upstream.
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: dd2776222abb ("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 Cc: Stephen Boyd swboyd@chromium.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- scripts/module.lds.S | 2 ++ 1 file changed, 2 insertions(+)
--- a/scripts/module.lds.S +++ b/scripts/module.lds.S @@ -26,6 +26,7 @@ SECTIONS {
__patchable_function_entries : { *(__patchable_function_entries) }
+#ifdef CONFIG_LTO_CLANG /* * With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and * -ffunction-sections, which increases the size of the final module. @@ -47,6 +48,7 @@ SECTIONS { }
.text : { *(.text .text.[0-9a-zA-Z_]*) } +#endif }
/* bring in arch-specific sections */