diff options
| author | Daniel Borkmann <daniel@iogearbox.net> | 2019-04-03 18:39:07 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-04-20 09:15:08 +0200 |
| commit | b101cf55c6da31b86ee8144ac0113b7ecfb7c06b (patch) | |
| tree | 708cfca6d862ea7aa24de9cafbbe9de279b1050a /include | |
| parent | ee282977c63d1c195ee0de6df173b0f216d14c28 (diff) | |
bpf: enable access to ax register also from verifier rewrite
commit 9b73bfdd08e73231d6a90ae6db4b46b3fbf56c30 upstream.
Right now we are using BPF ax register in JIT for constant blinding as
well as in interpreter as temporary variable. Verifier will not be able
to use it simply because its use will get overridden from the former in
bpf_jit_blind_insn(). However, it can be made to work in that blinding
will be skipped if there is prior use in either source or destination
register on the instruction. Taking constraints of ax into account, the
verifier is then open to use it in rewrites under some constraints. Note,
ax register already has mappings in every eBPF JIT.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
[backported to 4.14 sblbir]
Signed-off-by: Balbir Singh <sblbir@amzn.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/filter.h | 7 |
1 files changed, 1 insertions, 6 deletions
diff --git a/include/linux/filter.h b/include/linux/filter.h index f7880c716308..ac2272778f2e 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -46,12 +46,7 @@ struct bpf_prog_aux; #define BPF_REG_X BPF_REG_7 #define BPF_REG_TMP BPF_REG_8 -/* Kernel hidden auxiliary/helper register for hardening step. - * Only used by eBPF JITs. It's nothing more than a temporary - * register that JITs use internally, only that here it's part - * of eBPF instructions that have been rewritten for blinding - * constants. See JIT pre-step in bpf_jit_blind_constants(). - */ +/* Kernel hidden auxiliary/helper register. */ #define BPF_REG_AX MAX_BPF_REG #define MAX_BPF_EXT_REG (MAX_BPF_REG + 1) #define MAX_BPF_JIT_REG MAX_BPF_EXT_REG |