netdev - [bpf-next PATCH] bpf: add comments to BPF ld/ldx sizes

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Message-ID: <151618713588.21869.16178302277967693140.stgit@firesoul>
Date:   Wed, 17 Jan 2018 12:05:36 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     netdev@...r.kernel.org, Jesper Dangaard Brouer <brouer@...hat.com>
Subject: [bpf-next PATCH] bpf: add comments to BPF ld/ldx sizes

Doc BPF ld/ldx size defines as comments in code, as it makes in
faster to lookup in a programming/review setting, than looking up
the sizes in Documentation/networking/filter.txt.

Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
---
 include/uapi/linux/bpf.h        |    2 +-
 include/uapi/linux/bpf_common.h |    7 ++++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 395d261948de..4729d9a002d4 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -17,7 +17,7 @@
 #define BPF_ALU64	0x07	/* alu mode in double word width */
 
 /* ld/ldx fields */
-#define BPF_DW		0x18	/* double word */
+#define BPF_DW		0x18	/* double word (64-bit) */
 #define BPF_XADD	0xc0	/* exclusive add */
 
 /* alu/jmp fields */
diff --git a/include/uapi/linux/bpf_common.h b/include/uapi/linux/bpf_common.h
index 18be90725ab0..ee97668bdadb 100644
--- a/include/uapi/linux/bpf_common.h
+++ b/include/uapi/linux/bpf_common.h
@@ -15,9 +15,10 @@
 
 /* ld/ldx fields */
 #define BPF_SIZE(code)  ((code) & 0x18)
-#define		BPF_W		0x00
-#define		BPF_H		0x08
-#define		BPF_B		0x10
+#define		BPF_W		0x00 /* 32-bit */
+#define		BPF_H		0x08 /* 16-bit */
+#define		BPF_B		0x10 /*  8-bit */
+/* eBPF		BPF_DW		0x18    64-bit */
 #define BPF_MODE(code)  ((code) & 0xe0)
 #define		BPF_IMM		0x00
 #define		BPF_ABS		0x20