On 2022-01-28 19:19, Aurelien Jarno wrote:
On 2022-01-28 19:03, Heinrich Schuchardt wrote:
On 1/28/22 14:47, Alexandre Ghiti wrote:
The following description is copied from the equivalent patch for the Linux Kernel proposed by Aurelien Jarno:
From version 2.38, binutils default to ISA spec version 20191213. This means that the csr read/write (csrr*/csrw*) instructions and fence.i instruction has separated from the `I` extension, become two standalone extensions: Zicsr and Zifencei. As the kernel uses those instruction, this causes the following build failure:
arch/riscv/cpu/mtrap.S: Assembler messages: arch/riscv/cpu/mtrap.S:65: Error: unrecognized opcode `csrr a0,scause' arch/riscv/cpu/mtrap.S:66: Error: unrecognized opcode `csrr a1,sepc' arch/riscv/cpu/mtrap.S:67: Error: unrecognized opcode `csrr a2,stval' arch/riscv/cpu/mtrap.S:70: Error: unrecognized opcode `csrw sepc,a0'
I tried to build qemu-riscv64_smode_defconfig. With your patch I get
arch/riscv/cpu/cpu.c: Assembler messages: arch/riscv/cpu/cpu.c:94: Error: unrecognized opcode `csrs sstatus,a5' arch/riscv/cpu/cpu.c:95: Error: unrecognized opcode `csrw 0x003,0'
The build flag used is -march=rv64imac.
My toolchain is: binutils 2.37.90.20220126-0ubuntu1 riscv64-linux-gnu-gcc (Ubuntu 10.3.0-8ubuntu1) 10.3.0
This GCC does not support _zicsr_zifencei: cc1: error: ‘-march=rv64imac_zicsr_zifencei’: unsupported ISA subset ‘z
Could it be that the GCC is too old for the new binutils? When was the z subset added to GCC?
Yes, GCC 11 is the minimum version that understand those extensions.
GCC 11 is also required to support the not recommended alternative fix -misa-spec=2.2.
If you need to support GCC 10, it seems that the only option is to build binutils with --with-isa-spec=2.2.