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 02/13] bpf: x86: Factor out emission of REX byte
Date: Fri, 27 Nov 2020 17:57:27 +0000 [thread overview]
Message-ID: <20201127175738.1085417-3-jackmanb@google.com> (raw)
In-Reply-To: <20201127175738.1085417-1-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 94b17bd30e00..a839c1a54276 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -702,6 +702,21 @@ static void emit_modrm_dstoff(u8 **pprog, u32 r1, u32 r2, int off)
*pprog = prog;
}
+/*
+ * Emit a REX byte if it will be necessary to address these registers
+ */
+static void maybe_emit_rex(u8 **pprog, u32 reg_rm, u32 reg_reg, bool wide)
+{
+ u8 *prog = *pprog;
+ int cnt = 0;
+
+ if (wide)
+ EMIT1(add_2mod(0x48, reg_rm, reg_reg));
+ else if (is_ereg(reg_rm) || is_ereg(reg_reg))
+ EMIT1(add_2mod(0x40, reg_rm, reg_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_rex(&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_rex(&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_rex(&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_rex(&prog, dst_reg, dst_reg,
+ BPF_CLASS(insn->code) == BPF_JMP);
EMIT2(0x85, add_2reg(0xC0, dst_reg, dst_reg));
goto emit_cond_jmp;
}
--
2.29.2.454.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 ` Brendan Jackman [this message]
2020-11-29 1:14 ` [PATCH v2 bpf-next 02/13] bpf: x86: Factor out emission of REX byte 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
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=20201127175738.1085417-3-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).