bpf: provide helper that indicates eBPF was migrated

During recent discussions we had with Michael, we found that it would
be useful to have an indicator that tells the JIT that an eBPF program
had been migrated from classic instructions into eBPF instructions, as
only in that case A and X need to be cleared in the prologue. Such eBPF
programs do not set a particular type, but all have BPF_PROG_TYPE_UNSPEC.
Thus, introduce a small helper for cde66c2d88da ("s390/bpf: Only clear
A and X for converted BPF programs") and possibly others in future.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index bbbac6da37afedacfa3458f4bda8f5b1752a0477..9f4bbc09bf07b634092aede3058d89226ef60f97 100644 (file)
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -1245,7 +1245,7 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp)
        jit->lit = jit->lit_start;
        jit->prg = 0;
 
-       bpf_jit_prologue(jit, fp->type == BPF_PROG_TYPE_UNSPEC);
+       bpf_jit_prologue(jit, bpf_prog_was_classic(fp));
        for (i = 0; i < fp->len; i += insn_count) {
                insn_count = bpf_jit_insn(jit, fp, i);
                if (insn_count < 0)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 69d00555ce35239e8b93aa4b2a46fdb8171ca390..6b025491120d17e5a3bb676712100dc091e8a8de 100644 (file)
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -354,6 +354,16 @@ static inline unsigned int bpf_prog_size(unsigned int proglen)
                   offsetof(struct bpf_prog, insns[proglen]));
 }
 
+static inline bool bpf_prog_was_classic(const struct bpf_prog *prog)
+{
+       /* When classic BPF programs have been loaded and the arch
+        * does not have a classic BPF JIT (anymore), they have been
+        * converted via bpf_migrate_filter() to eBPF and thus always
+        * have an unspec program type.
+        */
+       return prog->type == BPF_PROG_TYPE_UNSPEC;
+}
+
 #define bpf_classic_proglen(fprog) (fprog->len * sizeof(fprog->filter[0]))
 
 #ifdef CONFIG_DEBUG_SET_MODULE_RONX