在 2025-05-29星期四的 10:02 +0800，Hengqi Chen写道： > Hi Haoran, > > On Wed, May 28, 2025 at 6:40 PM Haoran Jiang < > jianghaoran@xxxxxxxxxx > > wrote: > > For a ebpf subprog JIT，the last call bpf_int_jit_compile > > function will > > directly enter the skip_init_ctx process. At this point, > > out_offset = -1, > > the jmp_offset in emit_bpf_tail_call is calculated > > by #define jmp_offset (out_offset - (cur_offset)) is a negative > > number, > > which does not meet expectations.The final generated assembly > > as follow. > > > > 54: bgeu $a2, $t1, -8 # 0x0000004c > > 58: addi.d $a6, $s5, -1 > > 5c: bltz $a6, -16 # 0x0000004c > > 60: alsl.d $t2, $a2, $a1, 0x3 > > 64: ld.d $t2, $t2, 264 > > 68: beq $t2, $zero, -28 # 0x0000004c > > > > Before apply this patch, the follow test case will reveal soft > > lock issues. > > > > cd tools/testing/selftests/bpf/ > > ./test_progs --allow=tailcalls/tailcall_bpf2bpf_1 > > > > dmesg: > > watchdog: BUG: soft lockup - CPU#2 stuck for 26s! > > [test_progs:25056] > > > > This is a known issue. Does this change pass all tailcall tests ? > If not, please refer to the tailcall hierarchy patchset([1]). > We should address it once and for all. Thanks. > > [1]: > https://lore.kernel.org/bpf/20240714123902.32305-1-hffilwlqm@xxxxxxxxx/ > > Thanks,I'll keep looking into these patches. > > Signed-off-by: Haoran Jiang < > > jianghaoran@xxxxxxxxxx > > > > > --- > > arch/loongarch/net/bpf_jit.c | 28 +++++++++------------------- > > 1 file changed, 9 insertions(+), 19 deletions(-) > > > > diff --git a/arch/loongarch/net/bpf_jit.c > > b/arch/loongarch/net/bpf_jit.c > > index fa1500d4aa3e..d85490e7de89 100644 > > --- a/arch/loongarch/net/bpf_jit.c > > +++ b/arch/loongarch/net/bpf_jit.c > > @@ -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); > > @@ -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 > > @@ -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; > > @@ -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; > > > > @@ -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; > > @@ -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) > > @@ -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; > > > > @@ -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; > > > > -- > > 2.43.0 > >
