Re: [PATCH bpf-next 1/2] bpf,riscv: Implement PROBE_MEM32 pseudo instructions

From: Pu Lehui
Date: Sat Mar 23 2024 - 12:41:19 EST



On 2024/3/23 23:46, Puranjay Mohan wrote:
Add support for [LDX | STX | ST], PROBE_MEM32, [B | H | W | DW]
[snip]
#define BPF_FIXUP_OFFSET_MASK GENMASK(26, 0)
#define BPF_FIXUP_REG_MASK GENMASK(31, 27)
+#define DONT_CLEAR 16 /* RV_REG_A6 unused in BPF */

This is a bit misleading. RV_REG_A6 is actually used in riscv64. Maybe "RV_REG_A6 unused in pt_regmap" or change to other register will be better.

bool ex_handler_bpf(const struct exception_table_entry *ex,
[snip]
stack_adjust = round_up(stack_adjust, 16);
stack_adjust += bpf_stack_adjust;
@@ -1794,6 +1974,10 @@ void bpf_jit_build_prologue(struct rv_jit_context *ctx, bool is_subprog)
emit_sd(RV_REG_SP, store_offset, RV_REG_S6, ctx);
store_offset -= 8;
}
+ if (ctx->arena_vm_start) {
+ emit_sd(RV_REG_SP, store_offset, RV_REG_S11, ctx);
+ store_offset -= 8;
+ }

I think it's fine to use s7 and keep the original dynamic stack code style.

emit_addi(RV_REG_FP, RV_REG_SP, stack_adjust, ctx);
@@ -1807,6 +1991,9 @@ void bpf_jit_build_prologue(struct rv_jit_context *ctx, bool is_subprog)
emit_mv(RV_REG_TCC_SAVED, RV_REG_TCC, ctx);
ctx->stack_size = stack_adjust;
+
+ if (ctx->arena_vm_start)
+ emit_imm(RV_REG_S11, ctx->arena_vm_start, ctx);
}
void bpf_jit_build_epilogue(struct rv_jit_context *ctx)
diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c
index 6b3acac30c06..9b6696b1290a 100644
--- a/arch/riscv/net/bpf_jit_core.c
+++ b/arch/riscv/net/bpf_jit_core.c
@@ -50,6 +50,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
int pass = 0, prev_ninsns = 0, i;
struct rv_jit_data *jit_data;
struct rv_jit_context *ctx;
+ u64 arena_vm_start;

unused variable