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doc: Add info for building Xen target with Clang

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When build Xen target with Clang, the linker reports failure.

This patch adds the related info in the documentation as a known issue
and gives details for how to dismiss the building failure with Clang.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
This commit is contained in:
Leo Yan
2023-05-04 15:54:59 +08:00
committed by Tom Rini
parent 4787c764f9
commit e45fcb0e76
1 changed files with 36 additions and 0 deletions
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36
doc/build/clang.rst vendored
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@@ -74,3 +74,39 @@ simplified with a simple wrapper script - saved as
#!/bin/sh
exec clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd "$@"
Known Issues
------------
When build U-boot for `xenguest_arm64_defconfig` target, it reports linkage
error:
.. code-block:: bash
aarch64-linux-gnu-ld.bfd: drivers/xen/hypervisor.o: in function `do_hypervisor_callback':
/home/leoy/Dev2/u-boot/drivers/xen/hypervisor.c:188: undefined reference to `__aarch64_swp8_acq_rel'
aarch64-linux-gnu-ld.bfd: drivers/xen/hypervisor.o: in function `synch_test_and_set_bit':
/home/leoy/Dev2/u-boot/./arch/arm/include/asm/xen/system.h:40: undefined reference to `__aarch64_ldset1_acq_rel'
aarch64-linux-gnu-ld.bfd: drivers/xen/hypervisor.o: in function `synch_test_and_clear_bit':
/home/leoy/Dev2/u-boot/./arch/arm/include/asm/xen/system.h:28: undefined reference to `__aarch64_ldclr1_acq_rel'
aarch64-linux-gnu-ld.bfd: drivers/xen/hypervisor.o: in function `synch_test_and_set_bit':
/home/leoy/Dev2/u-boot/./arch/arm/include/asm/xen/system.h:40: undefined reference to `__aarch64_ldset1_acq_rel'
aarch64-linux-gnu-ld.bfd: drivers/xen/hypervisor.o: in function `synch_test_and_clear_bit':
/home/leoy/Dev2/u-boot/./arch/arm/include/asm/xen/system.h:28: undefined reference to `__aarch64_ldclr1_acq_rel'
aarch64-linux-gnu-ld.bfd: drivers/xen/events.o: in function `synch_test_and_clear_bit':
/home/leoy/Dev2/u-boot/./arch/arm/include/asm/xen/system.h:28: undefined reference to `__aarch64_ldclr1_acq_rel'
aarch64-linux-gnu-ld.bfd: drivers/xen/events.o: in function `synch_test_and_set_bit':
/home/leoy/Dev2/u-boot/./arch/arm/include/asm/xen/system.h:40: undefined reference to `__aarch64_ldset1_acq_rel'
aarch64-linux-gnu-ld.bfd: drivers/xen/gnttab.o: in function `gnttab_end_access':
/home/leoy/Dev2/u-boot/drivers/xen/gnttab.c:109: undefined reference to `__aarch64_cas2_acq_rel'
Segmentation fault
To fix the failure, we need to append option `-mno-outline-atomics` in Clang
command to not generate local calls to out-of-line atomic operations:
.. code-block:: bash
make HOSTCC=clang xenguest_arm64_defconfig
make HOSTCC=clang CROSS_COMPILE=aarch64-linux-gnu- \
CC="clang -target aarch64-linux-gnueabi -mno-outline-atomics" -j8