From 7b4f931bb1bd48fb28e088c33477756c66ea37ce Mon Sep 17 00:00:00 2001
From: Martin Teichmann <martin.teichmann@gmail.com>
Date: Tue, 7 Feb 2023 23:30:31 +0000
Subject: [PATCH] add an absolute value function
---
ebpfcat/ebpf.py | 20 ++++++++++++++++++++
ebpfcat/ebpf_test.py | 8 ++++++++
2 files changed, 28 insertions(+)
diff --git a/ebpfcat/ebpf.py b/ebpfcat/ebpf.py
index 15dea9d..b487b9b 100644
--- a/ebpfcat/ebpf.py
+++ b/ebpfcat/ebpf.py
@@ -460,6 +460,9 @@ class Expression:
def __neg__(self):
return Negate(self.ebpf, self)
+ def __abs__(self):
+ return Absolute(self.ebpf, self)
+
def __bool__(self):
raise AssembleError("Expression only has a value at execution time")
@@ -615,6 +618,23 @@ class Negate(Expression):
return self.arg.contains(no)
+class Absolute(Expression):
+ def __init__(self, ebpf, arg):
+ self.ebpf = ebpf
+ self.arg = arg
+
+ @contextmanager
+ def calculate(self, dst, long, signed, force=False):
+ with self.arg.calculate(dst, long, True, force) as \
+ (dst, long, signed):
+ with self.ebpf.r[dst] < 0:
+ self.ebpf.r[dst] = -self.ebpf.r[dst]
+ yield dst, long, True
+
+ def contains(self, no):
+ return self.arg.contains(no)
+
+
class Sum(Binary):
"""represent the sum of one register and a constant value
diff --git a/ebpfcat/ebpf_test.py b/ebpfcat/ebpf_test.py
index 4646af4..c8ee9f8 100644
--- a/ebpfcat/ebpf_test.py
+++ b/ebpfcat/ebpf_test.py
@@ -583,6 +583,14 @@ class Tests(TestCase):
Instruction(opcode=O.LONG+O.REG+O.MOV, dst=7, src=1, off=0, imm=0),
Instruction(opcode=O.LONG+O.NEG, dst=7, src=0, off=0, imm=0)])
+ def test_absolute(self):
+ e = EBPF()
+ e.r7 = abs(e.r1)
+ self.assertEqual(e.opcodes, [
+ Instruction(opcode=O.LONG+O.REG+O.MOV, dst=7, src=1, off=0, imm=0),
+ Instruction(opcode=O.JGE, dst=7, src=0, off=1, imm=0),
+ Instruction(opcode=O.LONG+O.NEG, dst=7, src=0, off=0, imm=0)])
+
def test_jump_data(self):
e = EBPF()
t1 = e.jumpIf(e.r1 > 0)
--
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