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commit c57cd4d45c4e54b3906171499258dbd3556855d4
Author: Oleksii Kurochko <oleksii.kurochko@gmail.com>
AuthorDate: Tue Apr 18 08:22:20 2023 +0200
Commit: Jan Beulich <jbeulich@suse.com>
CommitDate: Tue Apr 18 08:22:20 2023 +0200

xen/riscv: add EMBEDDED_EXTRA_CFLAGS to CFLAGS

The patch is needed to keep all address of cpu0_boot_stack
PC-relative.

Pseudoinstruction 'la' can be transformed to 'auipc/addi' or
'auipc/l{w|d}'. It depends on the .option directive: nopic and pic
or compiler flags.

Right now, 'la' transforms to 'auipc/l{w|d}', which in case of
cpu0_boot_stack[] will lead to the usage of _GLOBAL_OFFSET_TABLE_
where all addresses will be without counting that it might happen
that linker address != load address ( so addresses inside got
sections will be relative to linker time ).

It happens becuase the compiler from riscv64 docker compiled with
--enable-default-pie:
[user@49295ae49cbe build]$ riscv64-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=riscv64-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/riscv64-linux-gnu/12.2.0/lto-wrapper
Target: riscv64-linux-gnu
Configured with: /build/riscv64-linux-gnu-gcc/src/gcc-12.2.0/configure
--prefix=/usr --program-prefix=riscv64-linux-gnu- --with-local-
prefix=/usr/riscv64-linux-gnu --with-sysroot=/usr/riscv64-linux-gnu --
with-build-sysroot=/usr/riscv64-linux-gnu --libdir=/usr/lib --
libexecdir=/usr/lib --target=riscv64-linux-gnu --host=x86_64-pc-linux-
gnu --build=x86_64-pc-linux-gnu --with-system-zlib --with-isl --with-
linker-hash-style=gnu --disable-nls --disable-libunwind-exceptions --
disable-libstdcxx-pch --disable-libssp --disable-multilib --disable-
werror --enable-languages=c,c++ --enable-shared --enable-threads=posix
--enable-__cxa_atexit --enable-clocale=gnu --enable-gnu-unique-object -
-enable-linker-build-id --enable-lto --enable-plugin --enable-install-
libiberty --enable-gnu-indirect-function --enable-default-pie --enable-
checking=release
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.2.0 (GCC)

Looking at gcc spec file for the RISC-V architecture:
[user@49295ae49cbe build]$ riscv64-linux-gnu-gcc -dumpspecs | grep -i
pic
--traditional-format %(subtarget_asm_debugging_spec) %{fno-pie|fno-
PIE|fno-pic|fno-PIC:;:-fpic} %{march=*} %{mabi=*} %{mno-relax} %{mbig-
endian} %{mlittle-endian} %(subtarget_asm_spec)%{misa-spec=*}
which means that -fpic is enabled if none of the following options are
present on the command line:
-fno-pie
-fno-PIE
-fno-pic
-fno-PIC

That's the reasons why 'la' is transformed to 'aupic/l{w|d} GOT' and
not be dependent on the toolchain used.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
---
xen/arch/riscv/arch.mk | 2 ++
1 file changed, 2 insertions(+)

diff --git a/xen/arch/riscv/arch.mk b/xen/arch/riscv/arch.mk
index 45fe858ee0..7448f759b4 100644
--- a/xen/arch/riscv/arch.mk
+++ b/xen/arch/riscv/arch.mk
@@ -1,6 +1,8 @@
########################################
# RISCV-specific definitions

+$(call cc-options-add,CFLAGS,CC,$(EMBEDDED_EXTRA_CFLAGS))
+
CFLAGS-$(CONFIG_RISCV_64) += -mabi=lp64

riscv-march-$(CONFIG_RISCV_ISA_RV64G) := rv64g
--
generated by git-patchbot for /home/xen/git/xen.git#master