[xen master] xen/riscv: add EMBEDDED_EXTRA_CFLAGS to CFLAGS

[patchbot@xxxxxxx]

commit c57cd4d45c4e54b3906171499258dbd3556855d4
Author:     Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
AuthorDate: Tue Apr 18 08:22:20 2023 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
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@xxxxxxxx>
    Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Alistair Francis <alistair.francis@xxxxxxx>
---
 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
--
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