On 12/4/20 1:36 AM, Brendan Jackman wrote:
On Thu, Dec 03, 2020 at 10:42:19PM -0800, Yonghong Song wrote:
On 12/3/20 8:02 AM, Brendan Jackman wrote:
This adds instructions for
atomic[64]_[fetch_]and
atomic[64]_[fetch_]or
atomic[64]_[fetch_]xor
All these operations are isomorphic enough to implement with the same
verifier, interpreter, and x86 JIT code, hence being a single commit.
The main interesting thing here is that x86 doesn't directly support
the fetch_ version these operations, so we need to generate a CMPXCHG
loop in the JIT. This requires the use of two temporary registers,
IIUC it's safe to use BPF_REG_AX and x86's AUX_REG for this purpose.
Change-Id: I340b10cecebea8cb8a52e3606010cde547a10ed4
Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx>
---
arch/x86/net/bpf_jit_comp.c | 50 +++++++++++++++++++++++++++++-
include/linux/filter.h | 60 ++++++++++++++++++++++++++++++++++++
kernel/bpf/core.c | 5 ++-
kernel/bpf/disasm.c | 21 ++++++++++---
kernel/bpf/verifier.c | 6 ++++
tools/include/linux/filter.h | 60 ++++++++++++++++++++++++++++++++++++
6 files changed, 196 insertions(+), 6 deletions(-)
[...]
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 6186280715ed..698f82897b0d 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -280,6 +280,66 @@ static inline bool insn_is_zext(const struct bpf_insn *insn)
[...]
+#define BPF_ATOMIC_FETCH_XOR(SIZE, DST, SRC, OFF) \
+ ((struct bpf_insn) { \
+ .code = BPF_STX | BPF_SIZE(SIZE) | BPF_ATOMIC, \
+ .dst_reg = DST, \
+ .src_reg = SRC, \
+ .off = OFF, \
+ .imm = BPF_XOR | BPF_FETCH })
+
/* Atomic exchange, src_reg = atomic_xchg((dst_reg + off), src_reg) */
Looks like BPF_ATOMIC_XOR/OR/AND/... all similar to each other.
The same is for BPF_ATOMIC_FETCH_XOR/OR/AND/...
I am wondering whether it makes sence to have to
BPF_ATOMIC_BOP(BOP, SIZE, DST, SRC, OFF) and
BPF_ATOMIC_FETCH_BOP(BOP, SIZE, DST, SRC, OFF)
can have less number of macros?
Hmm yeah I think that's probably a good idea, it would be consistent
with the macros for non-atomic ALU ops.
I don't think 'BOP' would be very clear though, 'ALU' might be more
obvious.
BPF_ATOMIC_ALU and BPF_ATOMIC_FETCH_ALU indeed better.
