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 01/13] bpf: x86: Factor out emission of ModR/M for *(reg + off)
Date: Fri, 27 Nov 2020 17:57:26 +0000 [thread overview]
Message-ID: <20201127175738.1085417-2-jackmanb@google.com> (raw)
In-Reply-To: <20201127175738.1085417-1-jackmanb@google.com>
The case for JITing atomics is about to get more complicated. Let's
factor out some common code to make the review and result more
readable.
NB the atomics code doesn't yet use the new helper - a subsequent
patch will add its use as a side-effect of other changes.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
arch/x86/net/bpf_jit_comp.c | 42 +++++++++++++++++++++----------------
1 file changed, 24 insertions(+), 18 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 796506dcfc42..94b17bd30e00 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -681,6 +681,27 @@ static void emit_mov_reg(u8 **pprog, bool is64, u32 dst_reg, u32 src_reg)
*pprog = prog;
}
+/* Emit the ModR/M byte for addressing *(r1 + off) and r2 */
+static void emit_modrm_dstoff(u8 **pprog, u32 r1, u32 r2, int off)
+{
+ u8 *prog = *pprog;
+ int cnt = 0;
+
+ if (is_imm8(off)) {
+ /* 1-byte signed displacement.
+ *
+ * If off == 0 we could skip this and save one extra byte, but
+ * special case of x86 R13 which always needs an offset is not
+ * worth the hassle
+ */
+ EMIT2(add_2reg(0x40, r1, r2), off);
+ } else {
+ /* 4-byte signed displacement */
+ EMIT1_off32(add_2reg(0x80, r1, r2), off);
+ }
+ *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)
{
@@ -708,15 +729,7 @@ static void emit_ldx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
EMIT2(add_2mod(0x48, src_reg, dst_reg), 0x8B);
break;
}
- /*
- * If insn->off == 0 we can save one extra byte, but
- * special case of x86 R13 which always needs an offset
- * is not worth the hassle
- */
- if (is_imm8(off))
- EMIT2(add_2reg(0x40, src_reg, dst_reg), off);
- else
- EMIT1_off32(add_2reg(0x80, src_reg, dst_reg), off);
+ emit_modrm_dstoff(&prog, src_reg, dst_reg, off);
*pprog = prog;
}
@@ -751,10 +764,7 @@ static void emit_stx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
EMIT2(add_2mod(0x48, dst_reg, src_reg), 0x89);
break;
}
- if (is_imm8(off))
- EMIT2(add_2reg(0x40, dst_reg, src_reg), off);
- else
- EMIT1_off32(add_2reg(0x80, dst_reg, src_reg), off);
+ emit_modrm_dstoff(&prog, dst_reg, src_reg, off);
*pprog = prog;
}
@@ -1240,11 +1250,7 @@ st: if (is_imm8(insn->off))
goto xadd;
case BPF_STX | BPF_XADD | BPF_DW:
EMIT3(0xF0, add_2mod(0x48, dst_reg, src_reg), 0x01);
-xadd: if (is_imm8(insn->off))
- EMIT2(add_2reg(0x40, dst_reg, src_reg), insn->off);
- else
- EMIT1_off32(add_2reg(0x80, dst_reg, src_reg),
- insn->off);
+xadd: emit_modrm_dstoff(&prog, dst_reg, src_reg, insn->off);
break;
/* call */
--
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 ` Brendan Jackman [this message]
2020-11-29 1:15 ` [PATCH v2 bpf-next 01/13] bpf: x86: Factor out emission of ModR/M for *(reg + off) 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 ` [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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