From 6a3193cdd5e5b96ac65f04ee42555c216da332af Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Mon, 22 Mar 2021 16:44:38 -0700 Subject: 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: dd2776222abb ("kbuild: lto: merge module sections") Cc: Nick Desaulniers Signed-off-by: Sean Christopherson Reviewed-by: Sami Tolvanen Tested-by: Sami Tolvanen Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20210322234438.502582-1-seanjc@google.com --- scripts/module.lds.S | 2 ++ 1 file changed, 2 insertions(+) (limited to 'scripts') diff --git a/scripts/module.lds.S b/scripts/module.lds.S index 168cd27e6122..2c52535f9b56 100644 --- a/scripts/module.lds.S +++ b/scripts/module.lds.S @@ -20,6 +20,7 @@ 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. @@ -41,6 +42,7 @@ SECTIONS { } .text : { *(.text .text.[0-9a-zA-Z_]*) } +#endif } /* bring in arch-specific sections */ -- cgit v1.2.3