From 745abfaa9eafa597d31fdf24a3249e5206a98768 Mon Sep 17 00:00:00 2001 From: Luke Nelson Date: Mon, 20 Apr 2020 17:28:04 -0700 Subject: bpf, riscv: Fix tail call count off by one in RV32 BPF JIT This patch fixes an off by one error in the RV32 JIT handling for BPF tail call. Currently, the code decrements TCC before checking if it is less than zero. This limits the maximum number of tail calls to 32 instead of 33 as in other JITs. The fix is to instead check the old value of TCC before decrementing. Fixes: 5f316b65e99f ("riscv, bpf: Add RV32G eBPF JIT") Signed-off-by: Luke Nelson Signed-off-by: Alexei Starovoitov Acked-by: Xi Wang Link: https://lore.kernel.org/bpf/20200421002804.5118-1-luke.r.nels@gmail.com --- arch/riscv/net/bpf_jit_comp32.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'arch/riscv/net') diff --git a/arch/riscv/net/bpf_jit_comp32.c b/arch/riscv/net/bpf_jit_comp32.c index 302934177760..11083d4d5f2d 100644 --- a/arch/riscv/net/bpf_jit_comp32.c +++ b/arch/riscv/net/bpf_jit_comp32.c @@ -770,12 +770,13 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx) emit_bcc(BPF_JGE, lo(idx_reg), RV_REG_T1, off, ctx); /* - * if ((temp_tcc = tcc - 1) < 0) + * temp_tcc = tcc - 1; + * if (tcc < 0) * goto out; */ emit(rv_addi(RV_REG_T1, RV_REG_TCC, -1), ctx); off = (tc_ninsn - (ctx->ninsns - start_insn)) << 2; - emit_bcc(BPF_JSLT, RV_REG_T1, RV_REG_ZERO, off, ctx); + emit_bcc(BPF_JSLT, RV_REG_TCC, RV_REG_ZERO, off, ctx); /* * prog = array->ptrs[index]; -- cgit v1.2.3