netdev - [RFC PATCH bpf-next v1 08/14] MIPS: eBPF: support long jump for BPF

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sun, 11 Jul 2021 17:34:54 -0700
From:   Tony Ambardar <tony.ambardar@...il.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Paul Burton <paulburton@...nel.org>
Cc:     Tony Ambardar <Tony.Ambardar@...il.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-mips@...r.kernel.org,
        Johan Almbladh <johan.almbladh@...finetworks.com>,
        Hassan Naveed <hnaveed@...ecomp.com>,
        David Daney <ddaney@...iumnetworks.com>,
        Luke Nelson <luke.r.nels@...il.com>,
        Serge Semin <fancer.lancer@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>
Subject: [RFC PATCH bpf-next v1 08/14] MIPS: eBPF: support long jump for BPF_JMP|EXIT

Existing JIT code supports only short (18-bit) branches for BPF EXIT, and
results in some tests from module test_bpf not being jited. Update code
to fall back to long (28-bit) jumps if short branches are insufficient.

Before:
  test_bpf: #296 BPF_MAXINSNS: exec all MSH jited:0 1556004 PASS
  test_bpf: #297 BPF_MAXINSNS: ld_abs+get_processor_id jited:0 824957 PASS
  test_bpf: Summary: 378 PASSED, 0 FAILED, [364/366 JIT'ed]

After:
  test_bpf: #296 BPF_MAXINSNS: exec all MSH jited:1 221998 PASS
  test_bpf: #297 BPF_MAXINSNS: ld_abs+get_processor_id jited:1 490507 PASS
  test_bpf: Summary: 378 PASSED, 0 FAILED, [366/366 JIT'ed]

Fixes: b6bd53f9c4e8 ("MIPS: Add missing file for eBPF JIT.")
Signed-off-by: Tony Ambardar <Tony.Ambardar@...il.com>
---
 arch/mips/net/ebpf_jit.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c
index e8c403c6cfa3..f510c692975e 100644
--- a/arch/mips/net/ebpf_jit.c
+++ b/arch/mips/net/ebpf_jit.c
@@ -994,9 +994,14 @@ static int build_one_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
 	case BPF_JMP | BPF_EXIT:
 		if (this_idx + 1 < exit_idx) {
 			b_off = b_imm(exit_idx, ctx);
-			if (is_bad_offset(b_off))
-				return -E2BIG;
-			emit_instr(ctx, beq, MIPS_R_ZERO, MIPS_R_ZERO, b_off);
+			if (is_bad_offset(b_off)) {
+				target = j_target(ctx, exit_idx);
+				if (target == (unsigned int)-1)
+					return -E2BIG;
+				emit_instr(ctx, j, target);
+			} else {
+				emit_instr(ctx, b, b_off);
+			}
 			emit_instr(ctx, nop);
 		}
 		break;
-- 
2.25.1