[PATCH v2 13/28] kbuild: lto: merge module sections
From: Sami Tolvanen <samitolvanen@google.com>
Date: 2020-09-03 20:36:13
Also in:
linux-arch, linux-kbuild, linux-pci, lkml
Subsystem:
kernel build + files below scripts/ (unless maintained elsewhere), module support, the rest · Maintainers:
Nathan Chancellor, Nicolas Schier, Luis Chamberlain, Petr Pavlu, Daniel Gomez, Sami Tolvanen, Linus Torvalds
LLD always splits sections with LTO, which increases module sizes. This change adds a linker script that merges the split sections in the final module. Suggested-by: Nick Desaulniers <redacted> Signed-off-by: Sami Tolvanen <samitolvanen@google.com> --- Makefile | 2 ++ scripts/module-lto.lds | 26 ++++++++++++++++++++++++++ 2 files changed, 28 insertions(+) create mode 100644 scripts/module-lto.lds
diff --git a/Makefile b/Makefile
index c69e07bd506a..bb82a4323f1d 100644
--- a/Makefile
+++ b/Makefile@@ -921,6 +921,8 @@ CC_FLAGS_LTO_CLANG += -fvisibility=default # Limit inlining across translation units to reduce binary size LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5 KBUILD_LDFLAGS += $(LD_FLAGS_LTO_CLANG) + +KBUILD_LDS_MODULE += $(srctree)/scripts/module-lto.lds endif ifdef CONFIG_LTO
diff --git a/scripts/module-lto.lds b/scripts/module-lto.lds
new file mode 100644
index 000000000000..cbb11dc3639a
--- /dev/null
+++ b/scripts/module-lto.lds@@ -0,0 +1,26 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and + * -ffunction-sections, which increases the size of the final module. + * Merge the split sections in the final binary. + */ +SECTIONS { + __patchable_function_entries : { *(__patchable_function_entries) } + + .bss : { + *(.bss .bss.[0-9a-zA-Z_]*) + *(.bss..L*) + } + + .data : { + *(.data .data.[0-9a-zA-Z_]*) + *(.data..L*) + } + + .rodata : { + *(.rodata .rodata.[0-9a-zA-Z_]*) + *(.rodata..L*) + } + + .text : { *(.text .text.[0-9a-zA-Z_]*) } +}
--
2.28.0.402.g5ffc5be6b7-goog
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