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
next 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
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