Re: [PATCH 07/22] kbuild: lto: merge module sections
From: Nick Desaulniers <hidden>
Date: 2020-06-24 21:02:15
Also in:
linux-arch, linux-kbuild, linux-pci, lkml
On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen [off-list ref] wrote:
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 and discards the .eh_frame section that LLD may generate.
For discarding .eh_frame, Kees is currently fighting with a series that I would really like to see land that enables warnings on orphan section placement. I don't see any new flags to inhibit .eh_frame generation, or discard it in the linker script, so I'd expect it to be treated as an orphan section and kept. Was that missed, or should that be removed from the commit message?
quoted hunk ↗ jump to hunk
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.ldsdiff --git a/Makefile b/Makefile index ee66513a5b66..9ffec5fe1737 100644 --- a/Makefile +++ b/Makefile@@ -898,6 +898,8 @@ 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_LTOdiff --git a/scripts/module-lto.lds b/scripts/module-lto.lds new file mode 100644 index 000000000000..65884c652bf2 --- /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* .bss..compoundliteral*) + } + + .data : { + *(.data .data.[0-9a-zA-Z_]*) + *(.data..L* .data..compoundliteral*) + } + + .rodata : { + *(.rodata .rodata.[0-9a-zA-Z_]*) + *(.rodata..L* .rodata..compoundliteral*) + } + + .text : { *(.text .text.[0-9a-zA-Z_]*) } +} --2.27.0.212.ge8ba1cc988-goog
-- Thanks, ~Nick Desaulniers _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel