From: Brendan Jackman <jackmanb@google.com>
To: bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>, Yonghong Song <yhs@fb.com>,
Daniel Borkmann <daniel@iogearbox.net>,
KP Singh <kpsingh@chromium.org>,
Florent Revest <revest@chromium.org>,
linux-kernel@vger.kernel.org, Jann Horn <jannh@google.com>,
Brendan Jackman <jackmanb@google.com>
Subject: [PATCH v2 bpf-next 10/13] bpf: Add instructions for atomic[64]_[fetch_]sub
Date: Fri, 27 Nov 2020 17:57:35 +0000 [thread overview]
Message-ID: <20201127175738.1085417-11-jackmanb@google.com> (raw)
In-Reply-To: <20201127175738.1085417-1-jackmanb@google.com>
Including only interpreter and x86 JIT support.
x86 doesn't provide an atomic exchange-and-subtract instruction that
could be used for BPF_SUB | BPF_FETCH, however we can just emit a NEG
followed by an XADD to get the same effect.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
arch/x86/net/bpf_jit_comp.c | 16 ++++++++++++++--
include/linux/filter.h | 20 ++++++++++++++++++++
kernel/bpf/core.c | 1 +
kernel/bpf/disasm.c | 16 ++++++++++++----
kernel/bpf/verifier.c | 2 ++
tools/include/linux/filter.h | 20 ++++++++++++++++++++
6 files changed, 69 insertions(+), 6 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 7431b2937157..a8a9fab13fcf 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -823,6 +823,7 @@ static int emit_atomic(u8 **pprog, u8 atomic_op,
/* emit opcode */
switch (atomic_op) {
+ case BPF_SUB:
case BPF_ADD:
/* lock *(u32/u64*)(dst_reg + off) <op>= src_reg */
EMIT1(simple_alu_opcodes[atomic_op]);
@@ -1306,8 +1307,19 @@ st: if (is_imm8(insn->off))
case BPF_STX | BPF_ATOMIC | BPF_W:
case BPF_STX | BPF_ATOMIC | BPF_DW:
- err = emit_atomic(&prog, insn->imm, dst_reg, src_reg,
- insn->off, BPF_SIZE(insn->code));
+ if (insn->imm == (BPF_SUB | BPF_FETCH)) {
+ /*
+ * x86 doesn't have an XSUB insn, so we negate
+ * and XADD instead.
+ */
+ emit_neg(&prog, src_reg, BPF_SIZE(insn->code) == BPF_DW);
+ err = emit_atomic(&prog, BPF_ADD | BPF_FETCH,
+ dst_reg, src_reg, insn->off,
+ BPF_SIZE(insn->code));
+ } else {
+ err = emit_atomic(&prog, insn->imm, dst_reg, src_reg,
+ insn->off, BPF_SIZE(insn->code));
+ }
if (err)
return err;
break;
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 6186280715ed..a20a3a536bf5 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -280,6 +280,26 @@ static inline bool insn_is_zext(const struct bpf_insn *insn)
.off = OFF, \
.imm = BPF_ADD | BPF_FETCH })
+/* Atomic memory sub, *(uint *)(dst_reg + off16) -= src_reg */
+
+#define BPF_ATOMIC_SUB(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_SUB })
+
+/* Atomic memory sub with fetch, src_reg = atomic_fetch_sub(*(dst_reg + off), src_reg); */
+
+#define BPF_ATOMIC_FETCH_SUB(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_SUB | BPF_FETCH })
+
/* Atomic exchange, src_reg = atomic_xchg((dst_reg + off), src_reg) */
#define BPF_ATOMIC_XCHG(SIZE, DST, SRC, OFF) \
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 20a5351d1dc2..0f700464955f 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1650,6 +1650,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack)
STX_ATOMIC_W:
switch (IMM) {
ATOMIC(BPF_ADD, add)
+ ATOMIC(BPF_SUB, sub)
case BPF_XCHG:
if (BPF_SIZE(insn->code) == BPF_W)
diff --git a/kernel/bpf/disasm.c b/kernel/bpf/disasm.c
index 3441ac54ac65..f33acffdeed0 100644
--- a/kernel/bpf/disasm.c
+++ b/kernel/bpf/disasm.c
@@ -80,6 +80,11 @@ const char *const bpf_alu_string[16] = {
[BPF_END >> 4] = "endian",
};
+const char *const bpf_atomic_alu_string[16] = {
+ [BPF_ADD >> 4] = "add",
+ [BPF_SUB >> 4] = "sub",
+};
+
static const char *const bpf_ldst_string[] = {
[BPF_W >> 3] = "u32",
[BPF_H >> 3] = "u16",
@@ -154,17 +159,20 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs,
insn->dst_reg,
insn->off, insn->src_reg);
else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
- insn->imm == BPF_ADD) {
- verbose(cbs->private_data, "(%02x) lock *(%s *)(r%d %+d) += r%d\n",
+ (insn->imm == BPF_ADD || insn->imm == BPF_SUB)) {
+ verbose(cbs->private_data, "(%02x) lock *(%s *)(r%d %+d) %s r%d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg, insn->off,
+ bpf_alu_string[BPF_OP(insn->imm) >> 4],
insn->src_reg);
} else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
- insn->imm == (BPF_ADD | BPF_FETCH)) {
- verbose(cbs->private_data, "(%02x) r%d = atomic%s_fetch_add(*(%s *)(r%d %+d), r%d)\n",
+ (insn->imm == (BPF_ADD | BPF_FETCH) ||
+ insn->imm == (BPF_SUB | BPF_FETCH))) {
+ verbose(cbs->private_data, "(%02x) r%d = atomic%s_fetch_%s(*(%s *)(r%d %+d), r%d)\n",
insn->code, insn->src_reg,
BPF_SIZE(insn->code) == BPF_DW ? "64" : "",
+ bpf_atomic_alu_string[BPF_OP(insn->imm) >> 4],
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg, insn->off, insn->src_reg);
} else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c8311cc114ec..dea9ad486ad1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3606,6 +3606,8 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i
switch (insn->imm) {
case BPF_ADD:
case BPF_ADD | BPF_FETCH:
+ case BPF_SUB:
+ case BPF_SUB | BPF_FETCH:
case BPF_XCHG:
case BPF_CMPXCHG:
break;
diff --git a/tools/include/linux/filter.h b/tools/include/linux/filter.h
index ea99bd17d003..387eddaf11e5 100644
--- a/tools/include/linux/filter.h
+++ b/tools/include/linux/filter.h
@@ -190,6 +190,26 @@
.off = OFF, \
.imm = BPF_ADD | BPF_FETCH })
+/* Atomic memory sub, *(uint *)(dst_reg + off16) -= src_reg */
+
+#define BPF_ATOMIC_SUB(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_SUB })
+
+/* Atomic memory sub with fetch, src_reg = atomic_fetch_sub(*(dst_reg + off), src_reg); */
+
+#define BPF_ATOMIC_FETCH_SUB(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_SUB | BPF_FETCH })
+
/* Atomic exchange, src_reg = atomic_xchg((dst_reg + off), src_reg) */
#define BPF_ATOMIC_XCHG(SIZE, DST, SRC, OFF) \
--
2.29.2.454.gaff20da3a2-goog
next prev parent reply other threads:[~2020-11-27 17:58 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-27 17:57 [PATCH v2 bpf-next 00/13] Atomics for eBPF Brendan Jackman
2020-11-27 17:57 ` [PATCH v2 bpf-next 01/13] bpf: x86: Factor out emission of ModR/M for *(reg + off) Brendan Jackman
2020-11-29 1:15 ` Alexei Starovoitov
2020-12-01 12:14 ` Brendan Jackman
2020-12-02 5:50 ` Alexei Starovoitov
2020-12-02 10:52 ` Brendan Jackman
2020-12-02 17:35 ` Alexei Starovoitov
2020-11-27 17:57 ` [PATCH v2 bpf-next 02/13] bpf: x86: Factor out emission of REX byte Brendan Jackman
2020-11-29 1:14 ` Alexei Starovoitov
2020-12-01 12:12 ` Brendan Jackman
2020-12-02 5:48 ` Alexei Starovoitov
2020-12-02 10:54 ` Brendan Jackman
2020-11-27 17:57 ` [PATCH v2 bpf-next 03/13] bpf: x86: Factor out function to emit NEG Brendan Jackman
2020-11-27 17:57 ` [PATCH v2 bpf-next 04/13] bpf: x86: Factor out a lookup table for some ALU opcodes Brendan Jackman
2020-11-27 17:57 ` [PATCH v2 bpf-next 05/13] bpf: Rename BPF_XADD and prepare to encode other atomics in .imm Brendan Jackman
2020-11-28 3:43 ` Yonghong Song
2020-12-01 12:17 ` Brendan Jackman
2020-11-27 17:57 ` [PATCH v2 bpf-next 06/13] bpf: Move BPF_STX reserved field check into BPF_STX verifier code Brendan Jackman
2020-11-27 17:57 ` [PATCH v2 bpf-next 07/13] bpf: Add BPF_FETCH field / create atomic_fetch_add instruction Brendan Jackman
2020-11-28 4:15 ` Yonghong Song
2020-12-01 12:22 ` Brendan Jackman
2020-11-27 17:57 ` [PATCH v2 bpf-next 08/13] bpf: Add instructions for atomic_[cmp]xchg Brendan Jackman
2020-11-28 5:25 ` Yonghong Song
2020-12-01 12:27 ` Brendan Jackman
2020-11-29 1:27 ` Alexei Starovoitov
2020-12-01 12:32 ` Brendan Jackman
2020-11-27 17:57 ` [PATCH v2 bpf-next 09/13] bpf: Pull out a macro for interpreting atomic ALU operations Brendan Jackman
2020-11-27 17:57 ` Brendan Jackman [this message]
2020-11-27 21:39 ` [PATCH v2 bpf-next 10/13] bpf: Add instructions for atomic[64]_[fetch_]sub kernel test robot
2020-11-27 21:39 ` [RFC PATCH] bpf: bpf_atomic_alu_string[] can be static kernel test robot
2020-11-28 5:35 ` [PATCH v2 bpf-next 10/13] bpf: Add instructions for atomic[64]_[fetch_]sub Yonghong Song
2020-11-29 1:34 ` Alexei Starovoitov
2020-11-30 17:18 ` Yonghong Song
2020-12-01 12:38 ` Brendan Jackman
2020-12-02 5:55 ` Alexei Starovoitov
2020-12-02 11:19 ` Brendan Jackman
2020-11-27 17:57 ` [PATCH v2 bpf-next 11/13] bpf: Add bitwise atomic instructions Brendan Jackman
2020-11-28 5:39 ` Yonghong Song
2020-11-29 1:36 ` Alexei Starovoitov
2020-11-30 17:20 ` Yonghong Song
2020-11-27 17:57 ` [PATCH v2 bpf-next 12/13] bpf: Add tests for new BPF atomic operations Brendan Jackman
2020-12-01 3:55 ` Yonghong Song
2020-12-01 12:56 ` Brendan Jackman
2020-12-01 17:24 ` Yonghong Song
2020-12-02 2:22 ` Andrii Nakryiko
2020-12-02 12:26 ` Brendan Jackman
2020-11-27 17:57 ` [PATCH v2 bpf-next 13/13] bpf: Document new atomic instructions Brendan Jackman
2020-11-28 5:53 ` [PATCH v2 bpf-next 00/13] Atomics for eBPF Yonghong Song
2020-11-29 1:40 ` Alexei Starovoitov
2020-11-30 17:22 ` Yonghong Song
2020-12-01 3:48 ` Yonghong Song
2020-12-02 2:00 ` Andrii Nakryiko
2020-12-02 5:05 ` Yonghong Song
2020-12-02 5:53 ` John Fastabend
2020-12-02 5:59 ` Andrii Nakryiko
2020-12-02 6:27 ` John Fastabend
2020-12-02 8:03 ` Yonghong Song
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