wonderful-mobile/exynos-linux-stable
2
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

ANDROID: modpost: filter function/data section ldflags

Browse source 
The previous addition of -plugin-opt=-function-sections and
-plugin-opt=-data-sections to LDFLAGS when performing LTO with gold was
causing kernel modules to have individual sections for functions and
data. This means that rather than having multiple symbols in the
standard .text, .bss, and .data sections, there were now tens of
thousands of sections, each with one symbol. This was problematic for
third party tools used for parsing ramdumps that expect to find symbols
in the standard object layout.

This patch filters out these flags from LDFLAGS when constructing
modules.

Modules are linked in two phases with LTO.
1. produces <module>.lto.o
2. produces <module>.ko

We must not use these flags during BOTH links otherwise these objects
will have individual function and data sections.  Running `readelf -S`
on the above two files should show a number of sections in the order of
tens (vs. tens of thousands) for the tooling to work properly.

A more robust solution may be to look into is fixing the tooling to work
with function and data section object layouts, but this should fix the
tooling to work with the previous object layout for now.

Bug: 116819139
Bug: 119467548
Bug: 120503084
Change-Id: I2a388f42d5e460654de9cbd0b37dae4463bbb73e
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Rapherion Rollerscaperers <rapherion@raphielgang.org>
This commit is contained in:
Nick Desaulniers 2018-12-13 15:23:08 -08:00 • committed by xxmustafacooTR
parent 3caa54b873
commit 2c6dc3d015
No known key found for this signature in database
GPG key ID: 520B6FE385CBF5C9
1 changed files with 7 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

10
scripts/Makefile.modpost
View file

@ -88,8 +88,10 @@ modpost-ext = $(if $(CONFIG_LTO_CLANG),.lto,)
ifdef CONFIG_LTO_CLANG
quiet_cmd_cc_lto_link_modules = LD [M] $@
bad_ld_flags = -plugin-opt=-function-sections -plugin-opt=-data-sections
filtered_ld_flags = $(filter-out $(bad_ld_flags),$(ld_flags))
cmd_cc_lto_link_modules = \
$(LD) $(ld_flags) -r -o $(@) \
$(LD) $(filtered_ld_flags) -r -o $(@) \
$(shell [ -s $(@:$(modpost-ext).o=.o.symversions) ] && \
echo -T $(@:$(modpost-ext).o=.o.symversions)) \
--whole-archive $(filter-out FORCE,$^)
@ -136,8 +138,10 @@ ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
quiet_cmd_ld_ko_o = LD [M] $@
ifdef CONFIG_LTO_CLANG
cmd_ld_ko_o = \
$(LD) -r $(LDFLAGS) \
bad_ld_flags = -plugin-opt=-function-sections -plugin-opt=-data-sections
filtered_ldflags = $(filter-out $(bad_ld_flags),$(LDFLAGS))
cmd_ld_ko_o = \
$(LD) -r $(filtered_ld_flags) \
$(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE) \
$(shell [ -s $(@:.ko=.o.symversions) ] && \
echo -T $(@:.ko=.o.symversions)) \