diff options
| author |   Daniel Borkmann <daniel@iogearbox.net> | 2019-01-03 00:58:29 +0100 |
|---|---|---|
| committer |   Alexei Starovoitov <ast@kernel.org> | 2019-01-02 16:01:24 -0800 |
| commit | 9b73bfdd08e73231d6a90ae6db4b46b3fbf56c30 (patch) | |
| tree | 4f1d5e9561299532a0aba9a59496d488c27cfcda /include/linux/filter.h | |
| parent | bpf: move tmp variable into ax register in interpreter (diff) | |
| download | linux-dev-9b73bfdd08e73231d6a90ae6db4b46b3fbf56c30.tar.xz linux-dev-9b73bfdd08e73231d6a90ae6db4b46b3fbf56c30.zip | |
bpf: enable access to ax register also from verifier rewrite
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>
Diffstat (limited to 'include/linux/filter.h')
| -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 84a6a98f8328..ad106d845b22 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -53,12 +53,7 @@ struct sock_reuseport; #define BPF_REG_D BPF_REG_8 /* data, callee-saved */ #define BPF_REG_H BPF_REG_9 /* hlen, callee-saved */ -/* 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 |