From b7127cfea050a3b371d6da7a3ce9e69942f945f0 Mon Sep 17 00:00:00 2001 From: David Daney Date: Tue, 13 Jun 2017 16:49:36 -0700 Subject: [PATCH] test_bpf: Add test to make conditional jump cross a large number of insns. On MIPS, conditional branches can only span 32k instructions. To exceed this limit in the JIT with the BPF maximum of 4k insns, we need to choose eBPF insns that expand to more than 8 machine instructions. Use BPF_LD_ABS as it is quite complex. This forces the JIT to invert the sense of the branch to branch around a long jump to the end. This (somewhat) verifies that the branch inversion logic and target address calculation of the long jumps are done correctly. Signed-off-by: David Daney Acked-by: Daniel Borkmann Signed-off-by: David S. Miller --- lib/test_bpf.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/lib/test_bpf.c b/lib/test_bpf.c index 070bde56474c..c871e0e76c2a 100644 --- a/lib/test_bpf.c +++ b/lib/test_bpf.c @@ -435,6 +435,30 @@ static int bpf_fill_ld_abs_vlan_push_pop(struct bpf_test *self) return 0; } +static int bpf_fill_jump_around_ld_abs(struct bpf_test *self) +{ + unsigned int len = BPF_MAXINSNS; + struct bpf_insn *insn; + int i = 0; + + insn = kmalloc_array(len, sizeof(*insn), GFP_KERNEL); + if (!insn) + return -ENOMEM; + + insn[i++] = BPF_MOV64_REG(R6, R1); + insn[i++] = BPF_LD_ABS(BPF_B, 0); + insn[i] = BPF_JMP_IMM(BPF_JEQ, R0, 10, len - i - 2); + i++; + while (i < len - 1) + insn[i++] = BPF_LD_ABS(BPF_B, 1); + insn[i] = BPF_EXIT_INSN(); + + self->u.ptr.insns = insn; + self->u.ptr.len = len; + + return 0; +} + static int __bpf_fill_stxdw(struct bpf_test *self, int size) { unsigned int len = BPF_MAXINSNS; @@ -5044,6 +5068,14 @@ static struct bpf_test tests[] = { { { ETH_HLEN, 0xbef } }, .fill_helper = bpf_fill_ld_abs_vlan_push_pop, }, + { + "BPF_MAXINSNS: jump around ld_abs", + { }, + INTERNAL, + { 10, 11 }, + { { 2, 10 } }, + .fill_helper = bpf_fill_jump_around_ld_abs, + }, /* * LD_IND / LD_ABS on fragmented SKBs */ -- GitLab