https://sourceware.org/bugzilla/show_bug.cgi?id=23930
Bug ID: 23930
Summary: Problems linking objectfiles optimized for size (-Os)
Product: binutils
Version: 2.29
Status: NEW
Severity: normal
Priority: P2
Component: ld
Assignee: unassigned at sourceware dot org
Reporter: asavkov at redhat dot com
Target Milestone: ---
Created attachment 11416
--> https://sourceware.org/bugzilla/attachment.cgi?id=11416&action=edit
Reproducer
The issue was found while building linux kernel with
CONFIG_CC_OPTIMIZE_FOR_SIZE (adds -Os to cflags) and
KCFLAGS="-ffunction-sections", while linking vmlinux I get the fillowing
warnings and error:
ld: warning: dot moved backwards before `.text.__startup_secondary_64'
ld: warning: dot moved backwards before `.text.__startup_secondary_64'
ld: final link failed: File truncated
make: *** [Makefile:1032: vmlinux] Error 1
.iplt section seem to cause issues during linking. This is only reproducible
when vmas and lmas are different, failing section sh_addralign is 1(caused by
-Os) and .iplt is before failing section and the section offset needs to be
just right. I am attaching a small reproducer that I managed to put together
based on linux kernel linker script [1].
This is what I see happening:
.iplt does not have ignored flag set on first pass of
one_lang_size_sections_pass() but has it set on subsequent passes, this results
in dot of the following section moving backwards, resulting in a warning and
section lma not being set properly which later results in s_start being set to
a negative value in assign_file_positions_for_load_sections() yielding a "File
truncated" error.
I have bisected this issue to the following commit: 38b123494b "x86-64: Improve
PLT generation and synthetic PLT symbols"
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/kernel/vmlinux.lds.S
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