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From: Yonghong Song <yhs@fb.com>
To: <ast@fb.com>, <daniel@iogearbox.net>, <netdev@vger.kernel.org>
Cc: <kernel-team@fb.com>
Subject: [PATCH bpf-next v8 04/10] bpf: remove never-hit branches in verifier adjust_scalar_min_max_vals
Date: Sat, 28 Apr 2018 00:01:59 -0700	[thread overview]
Message-ID: <20180428070205.1059628-5-yhs@fb.com> (raw)
In-Reply-To: <20180428070205.1059628-1-yhs@fb.com>

In verifier function adjust_scalar_min_max_vals,
when src_known is false and the opcode is BPF_LSH/BPF_RSH,
early return will happen in the function. So remove
the branch in handling BPF_LSH/BPF_RSH when src_known is false.

Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
 kernel/bpf/verifier.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 988400e..6e3f859 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2940,10 +2940,7 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 			dst_reg->umin_value <<= umin_val;
 			dst_reg->umax_value <<= umax_val;
 		}
-		if (src_known)
-			dst_reg->var_off = tnum_lshift(dst_reg->var_off, umin_val);
-		else
-			dst_reg->var_off = tnum_lshift(tnum_unknown, umin_val);
+		dst_reg->var_off = tnum_lshift(dst_reg->var_off, umin_val);
 		/* We may learn something more from the var_off */
 		__update_reg_bounds(dst_reg);
 		break;
@@ -2971,11 +2968,7 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 		 */
 		dst_reg->smin_value = S64_MIN;
 		dst_reg->smax_value = S64_MAX;
-		if (src_known)
-			dst_reg->var_off = tnum_rshift(dst_reg->var_off,
-						       umin_val);
-		else
-			dst_reg->var_off = tnum_rshift(tnum_unknown, umin_val);
+		dst_reg->var_off = tnum_rshift(dst_reg->var_off, umin_val);
 		dst_reg->umin_value >>= umax_val;
 		dst_reg->umax_value >>= umin_val;
 		/* We may learn something more from the var_off */
-- 
2.9.5

  parent reply	other threads:[~2018-04-28  7:02 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-28  7:01 [PATCH bpf-next v8 00/10] bpf: add bpf_get_stack helper Yonghong Song
2018-04-28  7:01 ` [PATCH bpf-next v8 01/10] bpf: change prototype for stack_map_get_build_id_offset Yonghong Song
2018-04-28  7:01 ` [PATCH bpf-next v8 02/10] bpf: add bpf_get_stack helper Yonghong Song
2018-04-28  7:01 ` [PATCH bpf-next v8 03/10] bpf/verifier: refine retval R0 state for " Yonghong Song
2018-04-28  7:01 ` Yonghong Song [this message]
2018-04-28  7:02 ` [PATCH bpf-next v8 05/10] bpf/verifier: improve register value range tracking with ARSH Yonghong Song
2018-04-28 16:52   ` Alexei Starovoitov
2018-04-28  7:02 ` [PATCH bpf-next v8 06/10] tools/bpf: add bpf_get_stack helper to tools headers Yonghong Song
2018-04-28  7:02 ` [PATCH bpf-next v8 07/10] samples/bpf: move common-purpose trace functions to selftests Yonghong Song
2018-04-28  7:02 ` [PATCH bpf-next v8 08/10] tools/bpf: add a verifier test case for bpf_get_stack helper and ARSH Yonghong Song
2018-04-28  7:02 ` [PATCH bpf-next v8 09/10] tools/bpf: add a test for bpf_get_stack with raw tracepoint prog Yonghong Song
2018-04-28 16:56   ` Alexei Starovoitov
2018-04-28 18:17     ` Y Song
2018-04-28 19:06       ` Alexei Starovoitov
2018-04-28 20:02         ` Yonghong Song
2018-04-28  7:02 ` [PATCH bpf-next v8 10/10] tools/bpf: add a test for bpf_get_stack with " Yonghong Song

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