public inbox for bpf@vger.kernel.org
 help / color / mirror / Atom feed
From: Dave Thaler <dthaler1968@googlemail.com>
To: bpf@vger.kernel.org
Cc: bpf@ietf.org, Dave Thaler <dthaler@microsoft.com>
Subject: [PATCH bpf-next] bpf, docs: Add signed comparison example
Date: Fri, 10 Mar 2023 23:38:14 +0000	[thread overview]
Message-ID: <20230310233814.4641-1-dthaler1968@googlemail.com> (raw)

From: Dave Thaler <dthaler@microsoft.com>

Improve clarity by adding an example of a signed comparison instruction

Signed-off-by: Dave Thaler <dthaler@microsoft.com>
---
 Documentation/bpf/instruction-set.rst | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst
index 5e43e14abe8..b4464058905 100644
--- a/Documentation/bpf/instruction-set.rst
+++ b/Documentation/bpf/instruction-set.rst
@@ -11,7 +11,8 @@ Documentation conventions
 =========================
 
 For brevity, this document uses the type notion "u64", "u32", etc.
-to mean an unsigned integer whose width is the specified number of bits.
+to mean an unsigned integer whose width is the specified number of bits,
+and "s32", etc. to mean a signed integer of the specified number of bits.
 
 Registers and calling convention
 ================================
@@ -264,6 +265,14 @@ BPF_JSLE  0xd0   PC += off if dst <= src    signed
 The eBPF program needs to store the return value into register R0 before doing a
 BPF_EXIT.
 
+Example:
+
+``BPF_JSGE | BPF_X | BPF_JMP32`` (0x7e) means::
+
+  if (s32)dst s>= (s32)src goto +offset
+
+where 's>=' indicates a signed '>=' comparison.
+
 Helper functions
 ~~~~~~~~~~~~~~~~
 
-- 
2.33.4


             reply	other threads:[~2023-03-10 23:38 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-10 23:38 Dave Thaler [this message]
2023-03-11 19:27 ` [Bpf] [PATCH bpf-next] bpf, docs: Add signed comparison example David Vernet
2023-03-14  5:00 ` John Fastabend
2023-03-14  5:20 ` patchwork-bot+netdevbpf

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=20230310233814.4641-1-dthaler1968@googlemail.com \
    --to=dthaler1968@googlemail.com \
    --cc=bpf@ietf.org \
    --cc=bpf@vger.kernel.org \
    --cc=dthaler@microsoft.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