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[RFC,bpf-next,v1,07/14] MIPS: eBPF: fix MOD64 insn on R6 ISA

Message ID fdfdd33463f60cceb3f982aacd2229a1862a17d9.1625970384.git.Tony.Ambardar@gmail.com
State New
Headers show
Series MIPS: eBPF: refactor code, add MIPS32 JIT | expand

Commit Message

Tony Ambardar July 12, 2021, 12:34 a.m. UTC 
The BPF_ALU64 | BPF_MOD implementation is broken on MIPS64R6 due to use of
a 32-bit "modu" insn, as shown by the test_verifier failures:

  455/p MOD64 overflow, check 1 FAIL retval 0 != 1 (run 1/1)
  456/p MOD64 overflow, check 2 FAIL retval 0 != 1 (run 1/1)

Resolve by using the 64-bit "dmodu" instead.

Fixes: 6c2c8a188868 ("MIPS: eBPF: Provide eBPF support for MIPS64R6")
Signed-off-by: Tony Ambardar <Tony.Ambardar@gmail.com>
---
 arch/mips/net/ebpf_jit.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
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Patch

diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c
index 4f641dcb2031..e8c403c6cfa3 100644
--- a/arch/mips/net/ebpf_jit.c
+++ b/arch/mips/net/ebpf_jit.c
@@ -800,7 +800,7 @@  static int build_one_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
 			if (bpf_op == BPF_DIV)
 				emit_instr(ctx, ddivu_r6, dst, dst, MIPS_R_AT);
 			else
-				emit_instr(ctx, modu, dst, dst, MIPS_R_AT);
+				emit_instr(ctx, dmodu, dst, dst, MIPS_R_AT);
 			break;
 		}
 		emit_instr(ctx, ddivu, dst, MIPS_R_AT);
@@ -882,7 +882,7 @@  static int build_one_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
 					emit_instr(ctx, ddivu_r6,
 							dst, dst, src);
 				else
-					emit_instr(ctx, modu, dst, dst, src);
+					emit_instr(ctx, dmodu, dst, dst, src);
 				break;
 			}
 			emit_instr(ctx, ddivu, dst, src);