From: Paul Chaignon paul.chaignon@orange.com
[ Upstream commit e49e6f6db04e915dccb494ae10fa14888fea6f89 ]
All BPF JIT compilers except RISC-V's and MIPS' enforce a 33-tail calls limit at runtime. In addition, a test was recently added, in tailcalls2, to check this limit.
This patch updates the tail call limit in MIPS' JIT compiler to allow 33 tail calls.
Fixes: b6bd53f9c4e8 ("MIPS: Add missing file for eBPF JIT.") Reported-by: Mahshid Khezri khezri.mahshid@gmail.com Signed-off-by: Paul Chaignon paul.chaignon@orange.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Martin KaFai Lau kafai@fb.com Link: https://lore.kernel.org/bpf/b8eb2caac1c25453c539248e56ca22f74b5316af.1575916... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/mips/net/ebpf_jit.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c index 46b76751f3a5..3ec69d9cbe88 100644 --- a/arch/mips/net/ebpf_jit.c +++ b/arch/mips/net/ebpf_jit.c @@ -604,6 +604,7 @@ static void emit_const_to_reg(struct jit_ctx *ctx, int dst, u64 value) static int emit_bpf_tail_call(struct jit_ctx *ctx, int this_idx) { int off, b_off; + int tcc_reg;
ctx->flags |= EBPF_SEEN_TC; /* @@ -616,14 +617,14 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int this_idx) b_off = b_imm(this_idx + 1, ctx); emit_instr(ctx, bne, MIPS_R_AT, MIPS_R_ZERO, b_off); /* - * if (--TCC < 0) + * if (TCC-- < 0) * goto out; */ /* Delay slot */ - emit_instr(ctx, daddiu, MIPS_R_T5, - (ctx->flags & EBPF_TCC_IN_V1) ? MIPS_R_V1 : MIPS_R_S4, -1); + tcc_reg = (ctx->flags & EBPF_TCC_IN_V1) ? MIPS_R_V1 : MIPS_R_S4; + emit_instr(ctx, daddiu, MIPS_R_T5, tcc_reg, -1); b_off = b_imm(this_idx + 1, ctx); - emit_instr(ctx, bltz, MIPS_R_T5, b_off); + emit_instr(ctx, bltz, tcc_reg, b_off); /* * prog = array->ptrs[index]; * if (prog == NULL)