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authorSean Christopherson <seanjc@google.com>2021-03-22 16:44:38 -0700
committerKees Cook <keescook@chromium.org>2021-04-01 14:15:59 -0700
commit6a3193cdd5e5b96ac65f04ee42555c216da332af (patch)
treeb61f86cf72c116c8df62e778709fa3c8037db509
parenta5e13c6df0e41702d2b2c77c8ad41677ebb065b3 (diff)
downloadlinux-6a3193cdd5e5b96ac65f04ee42555c216da332af.tar.bz2
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 <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
-rw-r--r--scripts/module.lds.S2
1 files changed, 2 insertions, 0 deletions
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 */