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authorLuke Nelson <lukenels@cs.washington.edu>2020-04-21 03:28:04 +0300
committerAlexei Starovoitov <ast@kernel.org>2020-04-26 18:40:01 +0300
commit745abfaa9eafa597d31fdf24a3249e5206a98768 (patch)
tree7317971ec5e492834da0e4e0b0abd564995f32f8
parentae460c022453337850bdc36a36bf7596a6cfcf99 (diff)
downloadlinux-745abfaa9eafa597d31fdf24a3249e5206a98768.tar.xz
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 <luke.r.nels@gmail.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Xi Wang <xi.wang@gmail.com> Link: https://lore.kernel.org/bpf/20200421002804.5118-1-luke.r.nels@gmail.com
-rw-r--r--arch/riscv/net/bpf_jit_comp32.c5
1 files changed, 3 insertions, 2 deletions
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];