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LoongArch: BPF: Optimize the calculation method of jmp_offset in the emit_bpf_tail_call function #9013

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LoongArch: BPF: Optimize the calculation method of jmp_offset in the emit_bpf_tail_call function #9013

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28 changes: 9 additions & 19 deletions arch/loongarch/net/bpf_jit.c
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Original file line number Diff line number Diff line change
Expand Up @@ -208,9 +208,7 @@ bool bpf_jit_supports_far_kfunc_call(void)
return true;
}

/* initialized on the first pass of build_body() */
static int out_offset = -1;
static int emit_bpf_tail_call(struct jit_ctx *ctx)
static int emit_bpf_tail_call(int insn, struct jit_ctx *ctx)
{
int off;
u8 tcc = tail_call_reg(ctx);
Expand All @@ -220,9 +218,8 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
u8 t2 = LOONGARCH_GPR_T2;
u8 t3 = LOONGARCH_GPR_T3;
const int idx0 = ctx->idx;

#define cur_offset (ctx->idx - idx0)
#define jmp_offset (out_offset - (cur_offset))
int tc_ninsn = 0;
int jmp_offset = 0;

/*
* a0: &ctx
Expand All @@ -232,8 +229,11 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
* if (index >= array->map.max_entries)
* goto out;
*/
tc_ninsn = insn ? ctx->offset[insn+1] - ctx->offset[insn] :
ctx->offset[0];
off = offsetof(struct bpf_array, map.max_entries);
emit_insn(ctx, ldwu, t1, a1, off);
jmp_offset = tc_ninsn - (ctx->idx - idx0);
/* bgeu $a2, $t1, jmp_offset */
if (emit_tailcall_jmp(ctx, BPF_JGE, a2, t1, jmp_offset) < 0)
goto toofar;
Expand All @@ -243,6 +243,7 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
* goto out;
*/
emit_insn(ctx, addid, REG_TCC, tcc, -1);
jmp_offset = tc_ninsn - (ctx->idx - idx0);
if (emit_tailcall_jmp(ctx, BPF_JSLT, REG_TCC, LOONGARCH_GPR_ZERO, jmp_offset) < 0)
goto toofar;

Expand All @@ -254,6 +255,7 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
emit_insn(ctx, alsld, t2, a2, a1, 2);
off = offsetof(struct bpf_array, ptrs);
emit_insn(ctx, ldd, t2, t2, off);
jmp_offset = tc_ninsn - (ctx->idx - idx0);
/* beq $t2, $zero, jmp_offset */
if (emit_tailcall_jmp(ctx, BPF_JEQ, t2, LOONGARCH_GPR_ZERO, jmp_offset) < 0)
goto toofar;
Expand All @@ -263,22 +265,11 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx)
emit_insn(ctx, ldd, t3, t2, off);
__build_epilogue(ctx, true);

/* out: */
if (out_offset == -1)
out_offset = cur_offset;
if (cur_offset != out_offset) {
pr_err_once("tail_call out_offset = %d, expected %d!\n",
cur_offset, out_offset);
return -1;
}

return 0;

toofar:
pr_info_once("tail_call: jump too far\n");
return -1;
#undef cur_offset
#undef jmp_offset
}

static void emit_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
Expand Down Expand Up @@ -916,7 +907,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
/* tail call */
case BPF_JMP | BPF_TAIL_CALL:
mark_tail_call(ctx);
if (emit_bpf_tail_call(ctx) < 0)
if (emit_bpf_tail_call(i, ctx) < 0)
return -EINVAL;
break;

Expand Down Expand Up @@ -1342,7 +1333,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
if (tmp_blinded)
bpf_jit_prog_release_other(prog, prog == orig_prog ? tmp : orig_prog);

out_offset = -1;

return prog;

Expand Down
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