Fixing linker warnings #2012
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Fixing linker warnings #2012
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Starting with release 2.39 of the GNU Binutils, the ld linker warns with "missing .note.GNU-stack section implies executable stack" if it encounters an object file without a .note.GNU-stack section, and with "relocation in read-only section" if it encounters an object file containing a text relocation. In the both the kernel and the various bootloaders, such object files exist and are those built from assembly source files. The `-z noexecstack` linker option silences the first warning (and makes the linker assume that the output executable does not need an executable stack). The `-z notext` option silences the second warning (which does not reveal an actual issue, because the kernel is able to apply text relocations when doing KASLR). #1870
Starting with release 2.39 of the GNU Binutils, the linker warns when creating an ELF file containing a LOAD segment with RWX permissions (#1870). With the curent linker script for the x86 bootloader, the resulting ELF file contains such a segment. This change adds a PHDRS directive to the linker script and maps the different sections to the appropriate segments, so that no LOAD segments with RWX permissions exist in the stage2.elf file. This does not affet the final binary file of the bootloader, but silences the above warning. In addition, the SECTIONS directive of the linker script has been fixed so that all the input sections are mapped to the output sections specified in the script; this decreases by around 2% the size of the bootloader binary file. Closes #2010
This change amends the linker scripts for the klibs so that each klib ELF file has 3 segments: a text segment with read and execute permissions, a data segment with read-only permissions, and a data segment with read/write permissions. This avoids mapping an entire klib image with both write and execute permissions when the kernel loads a klib. In addition, the SECTIONS directive in the linker scripts has been fixed so that all the read-only input sections are mapped to the .text and .rodata output sections; this decreases the size of the klib ELF files.
eyberg
approved these changes
Mar 23, 2024
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This changeset fixes linker warnings that appeared starting with release 2.39 of the GNU binutils.
In addition, it amends the x86 bootloader linker script so that the size of the bootloader binary file is decreased by around 2%.
Closes #1870 and #2010