path: root/arch/sparc/net/bpf_jit_comp.c
diff options
authorEric Dumazet <edumazet@google.com>2014-01-15 06:50:07 -0800
committerDavid S. Miller <davem@davemloft.net>2014-01-15 17:02:08 -0800
commitaee636c4809fa54848ff07a899b326eb1f9987a2 (patch)
tree8f0c327f82dd7d5056dc487064f05f3f804f2fea /arch/sparc/net/bpf_jit_comp.c
parentbe2net: add dma_mapping_error() check for dma_map_page() (diff)
bpf: do not use reciprocal divide
At first Jakub Zawadzki noticed that some divisions by reciprocal_divide were not correct. (off by one in some cases) http://www.wireshark.org/~darkjames/reciprocal-buggy.c He could also show this with BPF: http://www.wireshark.org/~darkjames/set-and-dump-filter-k-bug.c The reciprocal divide in linux kernel is not generic enough, lets remove its use in BPF, as it is not worth the pain with current cpus. Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Jakub Zawadzki <darkjames-ws@darkjames.pl> Cc: Mircea Gherzan <mgherzan@gmail.com> Cc: Daniel Borkmann <dxchgb@gmail.com> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org> Cc: Matt Evans <matt@ozlabs.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: David S. Miller <davem@davemloft.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/sparc/net/bpf_jit_comp.c')
1 files changed, 14 insertions, 3 deletions
diff --git a/arch/sparc/net/bpf_jit_comp.c b/arch/sparc/net/bpf_jit_comp.c
index 218b6b23c378..01fe9946d388 100644
--- a/arch/sparc/net/bpf_jit_comp.c
+++ b/arch/sparc/net/bpf_jit_comp.c
@@ -497,9 +497,20 @@ void bpf_jit_compile(struct sk_filter *fp)
case BPF_S_ALU_MUL_K: /* A *= K */
emit_alu_K(MUL, K);
- case BPF_S_ALU_DIV_K: /* A /= K */
- emit_alu_K(MUL, K);
- emit_read_y(r_A);
+ case BPF_S_ALU_DIV_K: /* A /= K with K != 0*/
+ if (K == 1)
+ break;
+ emit_write_y(G0);
+#ifdef CONFIG_SPARC32
+ /* The Sparc v8 architecture requires
+ * three instructions between a %y
+ * register write and the first use.
+ */
+ emit_nop();
+ emit_nop();
+ emit_nop();
+ emit_alu_K(DIV, K);
case BPF_S_ALU_DIV_X: /* A /= X; */
emit_cmpi(r_X, 0);