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The Linux kernels ELF-FDPIC binfmt program loader can support loading and
running conventional ELF format binaries on noMMU kernels when compiled
appropriately. That is when they are constant displacement binaries such
as generated using the -pie compile option.
Add a configure option to allow selecting ELF binary support in noMMU
mode configurations on architectures that support this. The main
requirement is to generate the ldso run-time loader to perform relocation
at load time. These configurations do not support shared libraries, so
there is no need to generate a full shared library, only the static
version is required.
The use of ELF format binaries does mean a slightly simpler toolchain
generation (does not require a -uclinux- for some architectures) and does
not require an extra tool like elf2flt.
This initial support targets M68K, ARM and RISC-V architectures. No kernel
changes are required, the required support for this is already in mainline
kernels (certainly as of linux-6.6).
Note that for the M68K and ARM architectures that the initialized
registers and stack layout at process startup is slightly different for
the flat format loader and the ELF/ELF-FDPIC loaders. So we need some
changes to the startup code (crt1.S) for them.
I have not done extensive testing outside of M68K, ARM and RISC-V.
I had to make changes to a couple of the dl-startup.h architecture files
to get them to build for this noMMU case. I did not dig down too deep on
the reasons, but they still seem ok for the MMU case as well.
Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
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on i386, x86_64, and arm.
This patch adds the generation of rcrt1.o which is used by gcc when compiling with the --static-pie flag.
rcrt1.o differs from crt1.o and Scrt1.o in that it the executable has a dynamic section but no relocations have been performed prior to _start being called.
crt1.o assumes there to be no dynamic relocations, and Scrt1.o has all relocations performed prior to execution by lsdo.
The new reloc_static_pie function handles parsing the dynamic section, and performing the relocations in a architecture agnostic method.
It also sets _dl_load_base which is used when initalizing TLS to ensure loading from the proper location.
This allows for easier porting of static-pie support to additional architectures as only modifications to crt1.S to find the load address are required.
Signed-off-by: linted <linted@users.noreply.github.com>
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* ldso/ldso/arm/aeabi_read_tp.S: Add Thumb version.
* ldso/ldso/arm/dl-startup.h: Do not force ARM encoding, adjust
for Thumb.
* ldso/ldso/arm/resolve.S: Force Thumb encoding on Thumb-only
processors.
* libc/sysdeps/linux/arm/crt1.S: Do not force ARM encoding, adjust
for Thumb.
Signed-off-by: Mickaël Guêné <mickael.guene@st.com>
Signed-off-by: Christophe Lyon <christophe.lyon@st.com>
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* libc/sysdeps/linux/arm/crt1.S: Define _start for __FDPIC__.
Signed-off-by: Mickaël Guêné <mickael.guene@st.com>
Signed-off-by: Christophe Lyon <christophe.lyon@st.com>
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This matches a similar change made to glibc.
No functional changes here.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
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* fix a problem with Thumb PIE binaries,
where the GOT was located incorrectly because of an offset 8
Signed-off-by: Khem Raj <raj.khem@gmail.com>
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This patch fixes position-independent executables (PIEs) for Thumb-2. In
Thumb assembly, instructions reading pc give a value 4 greater than the
address of the instruction, rather than 8 greater as in ARM mode, so the
offset to the GOT needs to have the right offset. (The Thumb-1 code
already gets this right; it's the code shared by ARM and Thumb-2 that
needs fixing.)
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The attached patch adds support for compiling arm uClibc as pure Thumb code.
This is needed because some recent ARM codes do not implement traditional ARM
mode. Specifically:
* Cortex-M1 - An extremely minimal FPGA based core that only implements
Thumb-1 (aka ARMv6-M).
* Cortex-M3 - A Thumb-2 only ARMv7-M core.
Most of uClibc already builds in Thumb mode, all that is left are a handful of
assembly bits.
Tested on arm-uclinuxeabi.
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The patch below tweaks the ARM nommu startup code so that doubleword stack
alignment is preserved. This is required on EABI targets.
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__PIC__. Add these weaks to mips/crt1.S as well.
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properly with the new ABI
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has a chance of perhaps working...
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