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 bpf-next v4 02/11] bpf: x86: Factor out emission of REX byte
Date: Mon, 7 Dec 2020 16:07:25 +0000 [thread overview]
Message-ID: <20201207160734.2345502-3-jackmanb@google.com> (raw)
In-Reply-To: <20201207160734.2345502-1-jackmanb@google.com>
The JIT case for encoding atomic ops is about to get more
complicated. In order to make the review & resulting code easier,
let's factor out some shared helpers.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
arch/x86/net/bpf_jit_comp.c | 39 ++++++++++++++++++++++---------------
1 file changed, 23 insertions(+), 16 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index cc818ed7c2b9..7106cfd10ba6 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -702,6 +702,21 @@ static void emit_insn_suffix(u8 **pprog, u32 ptr_reg, u32 val_reg, int off)
*pprog = prog;
}
+/*
+ * Emit a REX byte if it will be necessary to address these registers
+ */
+static void maybe_emit_mod(u8 **pprog, u32 dst_reg, u32 src_reg, bool is64)
+{
+ u8 *prog = *pprog;
+ int cnt = 0;
+
+ if (is64)
+ EMIT1(add_2mod(0x48, dst_reg, src_reg));
+ else if (is_ereg(dst_reg) || is_ereg(src_reg))
+ EMIT1(add_2mod(0x40, dst_reg, src_reg));
+ *pprog = prog;
+}
+
/* LDX: dst_reg = *(u8*)(src_reg + off) */
static void emit_ldx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
{
@@ -854,10 +869,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
case BPF_OR: b2 = 0x09; break;
case BPF_XOR: b2 = 0x31; break;
}
- if (BPF_CLASS(insn->code) == BPF_ALU64)
- EMIT1(add_2mod(0x48, dst_reg, src_reg));
- else if (is_ereg(dst_reg) || is_ereg(src_reg))
- EMIT1(add_2mod(0x40, dst_reg, src_reg));
+ maybe_emit_mod(&prog, dst_reg, src_reg,
+ BPF_CLASS(insn->code) == BPF_ALU64);
EMIT2(b2, add_2reg(0xC0, dst_reg, src_reg));
break;
@@ -1301,20 +1314,16 @@ xadd: emit_modrm_dstoff(&prog, dst_reg, src_reg, insn->off);
case BPF_JMP32 | BPF_JSGE | BPF_X:
case BPF_JMP32 | BPF_JSLE | BPF_X:
/* cmp dst_reg, src_reg */
- if (BPF_CLASS(insn->code) == BPF_JMP)
- EMIT1(add_2mod(0x48, dst_reg, src_reg));
- else if (is_ereg(dst_reg) || is_ereg(src_reg))
- EMIT1(add_2mod(0x40, dst_reg, src_reg));
+ maybe_emit_mod(&prog, dst_reg, src_reg,
+ BPF_CLASS(insn->code) == BPF_JMP);
EMIT2(0x39, add_2reg(0xC0, dst_reg, src_reg));
goto emit_cond_jmp;
case BPF_JMP | BPF_JSET | BPF_X:
case BPF_JMP32 | BPF_JSET | BPF_X:
/* test dst_reg, src_reg */
- if (BPF_CLASS(insn->code) == BPF_JMP)
- EMIT1(add_2mod(0x48, dst_reg, src_reg));
- else if (is_ereg(dst_reg) || is_ereg(src_reg))
- EMIT1(add_2mod(0x40, dst_reg, src_reg));
+ maybe_emit_mod(&prog, dst_reg, src_reg,
+ BPF_CLASS(insn->code) == BPF_JMP);
EMIT2(0x85, add_2reg(0xC0, dst_reg, src_reg));
goto emit_cond_jmp;
@@ -1350,10 +1359,8 @@ xadd: emit_modrm_dstoff(&prog, dst_reg, src_reg, insn->off);
case BPF_JMP32 | BPF_JSLE | BPF_K:
/* test dst_reg, dst_reg to save one extra byte */
if (imm32 == 0) {
- if (BPF_CLASS(insn->code) == BPF_JMP)
- EMIT1(add_2mod(0x48, dst_reg, dst_reg));
- else if (is_ereg(dst_reg))
- EMIT1(add_2mod(0x40, dst_reg, dst_reg));
+ maybe_emit_mod(&prog, dst_reg, dst_reg,
+ BPF_CLASS(insn->code) == BPF_JMP);
EMIT2(0x85, add_2reg(0xC0, dst_reg, dst_reg));
goto emit_cond_jmp;
}
--
2.29.2.576.ga3fc446d84-goog
next prev parent reply other threads:[~2020-12-07 16:09 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-07 16:07 [PATCH bpf-next v4 00/11] Atomics for eBPF Brendan Jackman
2020-12-07 16:07 ` [PATCH bpf-next v4 01/11] bpf: x86: Factor out emission of ModR/M for *(reg + off) Brendan Jackman
2020-12-07 21:04 ` John Fastabend
2020-12-07 16:07 ` Brendan Jackman [this message]
2020-12-07 21:07 ` [PATCH bpf-next v4 02/11] bpf: x86: Factor out emission of REX byte John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 03/11] bpf: x86: Factor out a lookup table for some ALU opcodes Brendan Jackman
2020-12-07 21:08 ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 04/11] bpf: Rename BPF_XADD and prepare to encode other atomics in .imm Brendan Jackman
2020-12-07 21:56 ` John Fastabend
2020-12-08 9:26 ` Brendan Jackman
2020-12-09 5:40 ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 05/11] bpf: Move BPF_STX reserved field check into BPF_STX verifier code Brendan Jackman
2020-12-08 1:35 ` Yonghong Song
2020-12-08 5:13 ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 06/11] bpf: Add BPF_FETCH field / create atomic_fetch_add instruction Brendan Jackman
2020-12-08 1:41 ` Yonghong Song
2020-12-08 9:31 ` Brendan Jackman
2020-12-08 5:31 ` John Fastabend
2020-12-08 9:59 ` Brendan Jackman
2020-12-07 16:07 ` [PATCH bpf-next v4 07/11] bpf: Add instructions for atomic_[cmp]xchg Brendan Jackman
2020-12-08 1:44 ` Yonghong Song
2020-12-08 6:37 ` John Fastabend
2020-12-14 15:39 ` Brendan Jackman
2020-12-08 6:42 ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 08/11] bpf: Pull out a macro for interpreting atomic ALU operations Brendan Jackman
2020-12-07 16:07 ` [PATCH bpf-next v4 09/11] bpf: Add bitwise atomic instructions Brendan Jackman
2020-12-08 1:47 ` Yonghong Song
2020-12-10 0:22 ` kernel test robot
2020-12-07 16:07 ` [PATCH bpf-next v4 10/11] bpf: Add tests for new BPF atomic operations Brendan Jackman
2020-12-08 3:18 ` Yonghong Song
2020-12-08 12:41 ` Brendan Jackman
2020-12-08 16:38 ` Yonghong Song
2020-12-08 16:59 ` Brendan Jackman
2020-12-08 18:15 ` Yonghong Song
2020-12-15 11:12 ` Brendan Jackman
2020-12-16 7:18 ` Yonghong Song
2020-12-16 11:51 ` Brendan Jackman
2020-12-16 20:00 ` Yonghong Song
2020-12-07 16:07 ` [PATCH bpf-next v4 11/11] bpf: Document new atomic instructions Brendan Jackman
2020-12-08 3:25 ` Yonghong Song
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