From: Sean Christopherson <seanjc@xxxxxxxxxx> 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@xxxxxxxxxx> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> Reviewed-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx> Tested-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Link: https://lore.kernel.org/r/20210322234438.502582-1-seanjc@xxxxxxxxxx Cc: Stephen Boyd <swboyd@xxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 */ Patches currently in stable-queue which might be from seanjc@xxxxxxxxxx are queue-5.10/kbuild-lto-merge-module-sections-if-and-only-if-config_lto_clang-is-enabled.patch queue-5.10/revert-svm-add-warning-message-for-avic-ipi-invalid-target.patch