From 44b81136e86849117f34a083c359e4860662b3be Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Mon, 22 Mar 2021 16:44:38 -0700 Subject: [PATCH] kbuild: lto: Merge module sections if and only if CONFIG_LTO_CLANG is enabled 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 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 Cc: Stephen Boyd Signed-off-by: Greg Kroah-Hartman --- scripts/module.lds.S | 2 ++ 1 file changed, 2 insertions(+) diff --git a/scripts/module.lds.S b/scripts/module.lds.S index 18d5b8423635..c5f12195817b 100644 --- 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 */ -- 2.25.1