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authorSami Tolvanen <samitolvanen@google.com>2020-12-11 10:46:23 -0800
committerKees Cook <keescook@chromium.org>2021-01-14 08:21:09 -0800
commitfbe078d397b4d59232f05fde977d3b1e7d0c2028 (patch)
tree298965a7f44d326039861efb9a197839da21cc86
parentdd2776222abb9893e5b5c237a2c8c880d8854cee (diff)
kbuild: lto: add a default list of used symbols
With CONFIG_LTO_CLANG, LLVM bitcode has not yet been compiled into a binary when the .mod files are generated, which means they don't yet contain references to certain symbols that will be present in the final binaries. This includes intrinsic functions, such as memcpy, memmove, and memset [1], and stack protector symbols [2]. This change adds a default symbol list to use with CONFIG_TRIM_UNUSED_KSYMS when Clang's LTO is used. [1] https://llvm.org/docs/LangRef.html#standard-c-c-library-intrinsics [2] https://llvm.org/docs/LangRef.html#llvm-stackprotector-intrinsic Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20201211184633.3213045-7-samitolvanen@google.com
-rw-r--r--init/Kconfig1
-rw-r--r--scripts/lto-used-symbollist.txt5
2 files changed, 6 insertions, 0 deletions
diff --git a/init/Kconfig b/init/Kconfig
index b77c60f8b963..5271138b8742 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -2297,6 +2297,7 @@ config TRIM_UNUSED_KSYMS
config UNUSED_KSYMS_WHITELIST
string "Whitelist of symbols to keep in ksymtab"
depends on TRIM_UNUSED_KSYMS
+ default "scripts/lto-used-symbollist.txt" if LTO_CLANG
help
By default, all unused exported symbols will be un-exported from the
build when TRIM_UNUSED_KSYMS is selected.
diff --git a/scripts/lto-used-symbollist.txt b/scripts/lto-used-symbollist.txt
new file mode 100644
index 000000000000..38e7bb9ebaae
--- /dev/null
+++ b/scripts/lto-used-symbollist.txt
@@ -0,0 +1,5 @@
+memcpy
+memmove
+memset
+__stack_chk_fail
+__stack_chk_guard

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