bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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 11/13] bpf: Add bitwise atomic instructions
Date: Fri, 27 Nov 2020 17:57:36 +0000	[thread overview]
Message-ID: <20201127175738.1085417-12-jackmanb@google.com> (raw)
In-Reply-To: <20201127175738.1085417-1-jackmanb@google.com>

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.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 arch/x86/net/bpf_jit_comp.c  | 49 ++++++++++++++++++++++++++++-
 include/linux/filter.h       | 60 ++++++++++++++++++++++++++++++++++++
 kernel/bpf/core.c            |  5 ++-
 kernel/bpf/disasm.c          |  7 +++--
 kernel/bpf/verifier.c        |  6 ++++
 tools/include/linux/filter.h | 60 ++++++++++++++++++++++++++++++++++++
 6 files changed, 183 insertions(+), 4 deletions(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index a8a9fab13fcf..46b977ee21c4 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -823,8 +823,11 @@ static int emit_atomic(u8 **pprog, u8 atomic_op,
 
 	/* emit opcode */
 	switch (atomic_op) {
-	case BPF_SUB:
 	case BPF_ADD:
+	case BPF_SUB:
+	case BPF_AND:
+	case BPF_OR:
+	case BPF_XOR:
 		/* lock *(u32/u64*)(dst_reg + off) <op>= src_reg */
 		EMIT1(simple_alu_opcodes[atomic_op]);
 		break;
@@ -1307,6 +1310,50 @@ st:			if (is_imm8(insn->off))
 
 		case BPF_STX | BPF_ATOMIC | BPF_W:
 		case BPF_STX | BPF_ATOMIC | BPF_DW:
+			if (insn->imm == (BPF_AND | BPF_FETCH) ||
+			    insn->imm == (BPF_OR | BPF_FETCH) ||
+			    insn->imm == (BPF_XOR | BPF_FETCH)) {
+				u8 *branch_target;
+				bool is64 = BPF_SIZE(insn->code) == BPF_DW;
+
+				/*
+				 * Can't be implemented with a single x86 insn.
+				 * Need to do a CMPXCHG loop.
+				 */
+
+				/* Will need RAX as a CMPXCHG operand so save R0 */
+				emit_mov_reg(&prog, true, BPF_REG_AX, BPF_REG_0);
+				branch_target = prog;
+				/* Load old value */
+				emit_ldx(&prog, BPF_SIZE(insn->code),
+					 BPF_REG_0, dst_reg, insn->off);
+				/*
+				 * Perform the (commutative) operation locally,
+				 * put the result in the AUX_REG.
+				 */
+				emit_mov_reg(&prog, is64, AUX_REG, BPF_REG_0);
+				maybe_emit_rex(&prog, AUX_REG, src_reg, is64);
+				EMIT2(simple_alu_opcodes[BPF_OP(insn->imm)],
+				      add_2reg(0xC0, AUX_REG, src_reg));
+				/* Attempt to swap in new value */
+				err = emit_atomic(&prog, BPF_CMPXCHG,
+						  dst_reg, AUX_REG, insn->off,
+						  BPF_SIZE(insn->code));
+				if (WARN_ON(err))
+					return err;
+				/*
+				 * ZF tells us whether we won the race. If it's
+				 * cleared we need to try again.
+				 */
+				EMIT2(X86_JNE, -(prog - branch_target) - 2);
+				/* Return the pre-modification value */
+				emit_mov_reg(&prog, is64, src_reg, BPF_REG_0);
+				/* Restore R0 after clobbering RAX */
+				emit_mov_reg(&prog, true, BPF_REG_0, BPF_REG_AX);
+				break;
+
+			}
+
 			if (insn->imm == (BPF_SUB | BPF_FETCH)) {
 				/*
 				 * x86 doesn't have an XSUB insn, so we negate
diff --git a/include/linux/filter.h b/include/linux/filter.h
index a20a3a536bf5..cb5d865cce3c 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -300,6 +300,66 @@ static inline bool insn_is_zext(const struct bpf_insn *insn)
 		.off   = OFF,					\
 		.imm   = BPF_SUB | BPF_FETCH })
 
+/* Atomic memory and, *(uint *)(dst_reg + off16) -= src_reg */
+
+#define BPF_ATOMIC_AND(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_AND })
+
+/* Atomic memory and with fetch, src_reg = atomic_fetch_and(*(dst_reg + off), src_reg); */
+
+#define BPF_ATOMIC_FETCH_AND(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_AND | BPF_FETCH })
+
+/* Atomic memory or, *(uint *)(dst_reg + off16) -= src_reg */
+
+#define BPF_ATOMIC_OR(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_OR })
+
+/* Atomic memory or with fetch, src_reg = atomic_fetch_or(*(dst_reg + off), src_reg); */
+
+#define BPF_ATOMIC_FETCH_OR(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_OR | BPF_FETCH })
+
+/* Atomic memory xor, *(uint *)(dst_reg + off16) -= src_reg */
+
+#define BPF_ATOMIC_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 })
+
+/* Atomic memory xor with fetch, src_reg = atomic_fetch_xor(*(dst_reg + off), src_reg); */
+
+#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) */
 
 #define BPF_ATOMIC_XCHG(SIZE, DST, SRC, OFF)			\
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 0f700464955f..d5f4b1f2c9fe 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1651,7 +1651,10 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack)
 		switch (IMM) {
 		ATOMIC(BPF_ADD, add)
 		ATOMIC(BPF_SUB, sub)
-
+		ATOMIC(BPF_AND, and)
+		ATOMIC(BPF_OR, or)
+		ATOMIC(BPF_XOR, xor)
+#undef ATOMIC
 		case BPF_XCHG:
 			if (BPF_SIZE(insn->code) == BPF_W)
 				SRC = (u32) atomic_xchg(
diff --git a/kernel/bpf/disasm.c b/kernel/bpf/disasm.c
index f33acffdeed0..4c861632efac 100644
--- a/kernel/bpf/disasm.c
+++ b/kernel/bpf/disasm.c
@@ -83,6 +83,7 @@ const char *const bpf_alu_string[16] = {
 const char *const bpf_atomic_alu_string[16] = {
 	[BPF_ADD >> 4]  = "add",
 	[BPF_SUB >> 4]  = "sub",
+	[BPF_AND >> 4]  = "and",
 };
 
 static const char *const bpf_ldst_string[] = {
@@ -159,7 +160,8 @@ 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 || insn->imm == BPF_SUB)) {
+			 (insn->imm == BPF_ADD || insn->imm == BPF_SUB ||
+			  (insn->imm == BPF_AND))) {
 			verbose(cbs->private_data, "(%02x) lock *(%s *)(r%d %+d) %s r%d\n",
 				insn->code,
 				bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
@@ -168,7 +170,8 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs,
 				insn->src_reg);
 		} else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
 			   (insn->imm == (BPF_ADD | BPF_FETCH) ||
-			    insn->imm == (BPF_SUB | BPF_FETCH))) {
+			    insn->imm == (BPF_SUB | BPF_FETCH) ||
+			    insn->imm == (BPF_AND | 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" : "",
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index dea9ad486ad1..188f152a0c32 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3608,6 +3608,12 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i
 	case BPF_ADD | BPF_FETCH:
 	case BPF_SUB:
 	case BPF_SUB | BPF_FETCH:
+	case BPF_AND:
+	case BPF_AND | BPF_FETCH:
+	case BPF_OR:
+	case BPF_OR | BPF_FETCH:
+	case BPF_XOR:
+	case BPF_XOR | BPF_FETCH:
 	case BPF_XCHG:
 	case BPF_CMPXCHG:
 		break;
diff --git a/tools/include/linux/filter.h b/tools/include/linux/filter.h
index 387eddaf11e5..2a64149af056 100644
--- a/tools/include/linux/filter.h
+++ b/tools/include/linux/filter.h
@@ -210,6 +210,66 @@
 		.off   = OFF,					\
 		.imm   = BPF_SUB | BPF_FETCH })
 
+/* Atomic memory and, *(uint *)(dst_reg + off16) -= src_reg */
+
+#define BPF_ATOMIC_AND(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_AND })
+
+/* Atomic memory and with fetch, src_reg = atomic_fetch_and(*(dst_reg + off), src_reg); */
+
+#define BPF_ATOMIC_FETCH_AND(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_AND | BPF_FETCH })
+
+/* Atomic memory or, *(uint *)(dst_reg + off16) -= src_reg */
+
+#define BPF_ATOMIC_OR(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_OR })
+
+/* Atomic memory or with fetch, src_reg = atomic_fetch_or(*(dst_reg + off), src_reg); */
+
+#define BPF_ATOMIC_FETCH_OR(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_OR | BPF_FETCH })
+
+/* Atomic memory xor, *(uint *)(dst_reg + off16) -= src_reg */
+
+#define BPF_ATOMIC_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 })
+
+/* Atomic memory xor with fetch, src_reg = atomic_fetch_xor(*(dst_reg + off), src_reg); */
+
+#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) */
 
 #define BPF_ATOMIC_XCHG(SIZE, DST, SRC, OFF)			\
-- 
2.29.2.454.gaff20da3a2-goog


  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 ` [PATCH v2 bpf-next 10/13] bpf: Add instructions for atomic[64]_[fetch_]sub Brendan Jackman
2020-11-27 21:39   ` 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 ` Brendan Jackman [this message]
2020-11-28  5:39   ` [PATCH v2 bpf-next 11/13] bpf: Add bitwise atomic instructions 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20201127175738.1085417-12-jackmanb@google.com \
    --to=jackmanb@google.com \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=jannh@google.com \
    --cc=kpsingh@chromium.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=revest@chromium.org \
    --cc=yhs@fb.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).