riscv: compat: vdso: Add COMPAT_VDSO base code implementation
There is no vgettimeofday supported in rv32 that makes simple to
generate rv32 vdso code which only needs riscv64 compiler. Other
architectures need change compiler or -m (machine parameter) to
support vdso32 compiling. If rv32 support vgettimeofday (which
cause C compile) in future, we would add CROSS_COMPILE to support
that makes more requirement on compiler enviornment.
linux-rv64/arch/riscv/kernel/compat_vdso/compat_vdso.so.dbg:
file format elf64-littleriscv
Disassembly of section .text:
0000000000000800 <__vdso_rt_sigreturn>:
800:
08b00893 li a7,139
804:
00000073 ecall
808: 0000 unimp
...
000000000000080c <__vdso_getcpu>:
80c:
0a800893 li a7,168
810:
00000073 ecall
814: 8082 ret
...
0000000000000818 <__vdso_flush_icache>:
818:
10300893 li a7,259
81c:
00000073 ecall
820: 8082 ret
linux-rv32/arch/riscv/kernel/vdso/vdso.so.dbg:
file format elf32-littleriscv
Disassembly of section .text:
00000800 <__vdso_rt_sigreturn>:
800:
08b00893 li a7,139
804:
00000073 ecall
808: 0000 unimp
...
0000080c <__vdso_getcpu>:
80c:
0a800893 li a7,168
810:
00000073 ecall
814: 8082 ret
...
00000818 <__vdso_flush_icache>:
818:
10300893 li a7,259
81c:
00000073 ecall
820: 8082 ret
Finally, reuse all *.S from vdso in compat_vdso that makes
implementation clear and readable.
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20220405071314.3225832-17-guoren@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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