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[RFC,bpf-next,v1,08/14] MIPS: eBPF: support long jump for BPF_JMP|EXIT

Message ID 068c7d433d5ca78e791827f93275474fec64ef6d.1625970384.git.Tony.Ambardar@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series MIPS: eBPF: refactor code, add MIPS32 JIT | expand

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netdev/tree_selection success Clearly marked for bpf-next
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netdev/cc_maintainers fail 2 blamed authors not CCed: david.daney@cavium.com davem@davemloft.net; 2 maintainers not CCed: davem@davemloft.net david.daney@cavium.com
netdev/source_inline success Was 0 now: 0
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netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/kdoc success Errors and warnings before: 4 this patch: 4
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netdev/checkpatch warning WARNING: From:/Signed-off-by: email address mismatch: 'From: Tony Ambardar <tony.ambardar@gmail.com>' != 'Signed-off-by: Tony Ambardar <Tony.Ambardar@gmail.com>'
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
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Commit Message

Tony Ambardar July 12, 2021, 12:34 a.m. UTC
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@gmail.com>
---
 arch/mips/net/ebpf_jit.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
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Patch

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;