From 2422a15c80815718ce6c3e1528822676dcc65407 Mon Sep 17 00:00:00 2001
From: Martin Teichmann <martin.teichmann@xfel.eu>
Date: Mon, 21 Dec 2020 02:36:22 +0000
Subject: [PATCH] the start of ebpf
---
__init__.py | 0
bpf.py | 45 +++++++++++++++++
ebpf.py | 139 +++++++++++++++++++++++++++++++++++++++++++++++++++
ebpf_test.py | 79 +++++++++++++++++++++++++++++
4 files changed, 263 insertions(+)
create mode 100644 __init__.py
create mode 100644 bpf.py
create mode 100644 ebpf.py
create mode 100644 ebpf_test.py
diff --git a/__init__.py b/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/bpf.py b/bpf.py
new file mode 100644
index 0000000..4d1cf1a
--- /dev/null
+++ b/bpf.py
@@ -0,0 +1,45 @@
+from ctypes import CDLL, c_int, get_errno, cast, c_void_p, create_string_buffer
+from struct import pack
+
+from os import strerror
+
+libc = CDLL("libc.so.6", use_errno=True)
+
+def addrof(ptr):
+ return cast(ptr, c_void_p).value
+
+def bpf(cmd, fmt, *args):
+ attr = pack(fmt, *args)
+ ret = libc.syscall(386, c_int(cmd), attr, len(attr))
+ if ret == -1:
+ raise OSError(get_errno(), strerror(get_errno()))
+ return ret
+
+def create_map(map_type, key_size, value_size, max_entries):
+ return bpf(0, "IIII", map_type, key_size, value_size, max_entries)
+
+def lookup_elem(fd, key, size):
+ value = create_string_buffer(size)
+ bpf(1, "IQQQ", fd, addrof(key), addrof(value), 0)
+ return value.value
+
+def update_elem(fd, key, value, flags):
+ return bpf(2, "IQQQ", fd, addrof(key), addrof(value), flags)
+
+def prog_load(prog_type, insns, license,
+ log_level=0, log_size=4096, kern_version=0):
+ if log_level == 0:
+ log_buf = 0
+ log_size = 0
+ else:
+ log_buf = addrof(create_string_buffer(log_size))
+ license = license.encode("utf8")
+ bpf(5, "IIQQIIQI", prog_type, int(len(insns) // 8), addrof(license),
+ log_level, log_size, log_buf, kern_version)
+ if log_level != 0:
+ return log_buf.value
+
+if __name__ == "__main__":
+ fd = create_map(1, 4, 4, 10)
+ update_elem(fd, b"asdf", b"ckde", 0)
+ print(lookup_elem(fd, b"asdf", 4))
diff --git a/ebpf.py b/ebpf.py
new file mode 100644
index 0000000..adda0fa
--- /dev/null
+++ b/ebpf.py
@@ -0,0 +1,139 @@
+from collections import namedtuple
+from struct import pack
+
+from .bpf import prog_load
+
+Instruction = namedtuple("Instruction",
+ ["opcode", "dst", "src", "off", "imm"])
+
+def augassign(opcode):
+ def ret(self, value):
+ if isinstance(value, int):
+ return Instruction(opcode + 3 * self.long, self.no, 0, 0, value)
+ elif isinstance(value, Register) and self.long == value.long:
+ return Instruction(opcode + 8 + 3 * self.long,
+ self.no, value.no, 0, 0)
+ else:
+ return NotImplemented
+ return ret
+
+
+class Sum:
+ def __init__(self, no, offset):
+ self.no = no
+ self.offset = offset
+
+ def __add__(self, value):
+ if isinstance(value, int):
+ return Sum(self.no, self.offset + value)
+ else:
+ return NotImplemented
+
+ __radd__ = __add__
+
+ def __sub__(self, value):
+ if isinstance(value, int):
+ return Sum(self.no, self.offset - value)
+ else:
+ return NotImplemented
+
+
+class Register:
+ offset = 0
+
+ def __init__(self, no, ebpf, long):
+ self.no = no
+ self.ebpf = ebpf
+ self.long = long
+
+ __iadd__ = augassign(4)
+ __isub__ = augassign(0x14)
+ __imul__ = augassign(0x24)
+ __itruediv__ = augassign(0x34)
+ __ior__ = augassign(0x44)
+ __iand__ = augassign(0x54)
+ __ilshift__ = augassign(0x64)
+ __irshift__ = augassign(0x74)
+ __imod__ = augassign(0x94)
+ __ixor__ = augassign(0xa4)
+
+ def __add__(self, value):
+ if isinstance(value, int) and self.long:
+ return Sum(self.no, value)
+ else:
+ return NotImplemented
+
+ __radd__ = __add__
+
+ def __sub__(self, value):
+ if isinstance(value, int) and self.long:
+ return Sum(self.no, -value)
+ else:
+ return NotImplemented
+
+
+class Memory:
+ def __init__(self, ebpf, bits):
+ self.ebpf = ebpf
+ self.bits = bits
+
+ def __setitem__(self, addr, value):
+ if isinstance(value, int):
+ self.ebpf.append(0x62 + self.bits, addr.no, 0, addr.offset, value)
+ elif isinstance(value, Register):
+ self.ebpf.append(0x63 + self.bits, addr.no, value.no,
+ addr.offset, 0)
+ else:
+ raise RuntimeError("cannot compile")
+
+ def __getitem__(self, addr):
+ pass
+
+
+class RegisterDesc:
+ def __init__(self, no, long):
+ self.no = no
+ self.long = long
+
+ def __get__(self, instance, owner=None):
+ if instance is None:
+ return self
+ else:
+ return Register(self.no, instance, self.long)
+
+ def __set__(self, instance, value):
+ if isinstance(value, int):
+ instance.append(0xb4 + 3 * self.long, self.no, 0, 0, value)
+ elif isinstance(value, Register) and self.long == value.long:
+ instance.append(0xbc + 3 * self.long, self.no, value.no, 0, 0)
+ elif isinstance(value, Instruction):
+ instance.opcodes.append(value)
+ else:
+ raise RuntimeError("cannot compile")
+
+
+class EBPF:
+ def __init__(self, prog_type=0, license="", kern_version=0):
+ self.opcodes = []
+ self.prog_type = prog_type
+ self.license = license
+ self.kern_version = kern_version
+
+ def append(self, opcode, dst, src, off, imm):
+ self.opcodes.append(Instruction(opcode, dst, src, off, imm))
+
+ def assemble(self):
+ return b"".join(
+ pack("<BBHI", i.opcode, i.dst << 4 | i.src, i.off, i.imm)
+ for i in self.opcodes)
+
+ def load(self, log_level=0, log_size=4096):
+ return prog_load(self.prog_type, self.assemble(), self.license,
+ log_level, log_size, self.kern_version)
+
+
+for i in range(10):
+ setattr(EBPF, f"r{i}", RegisterDesc(i, True))
+
+for i in range(10):
+ setattr(EBPF, f"s{i}", RegisterDesc(i, False))
diff --git a/ebpf_test.py b/ebpf_test.py
new file mode 100644
index 0000000..7b3ff93
--- /dev/null
+++ b/ebpf_test.py
@@ -0,0 +1,79 @@
+from unittest import TestCase, main
+
+from .ebpf import EBPF, Instruction
+
+
+class Tests(TestCase):
+ def test_assemble(self):
+ e = EBPF()
+ e.append(0x24, 3, 4, 0x2c3d, 0x2d3e4f5e)
+ self.assertEqual(e.assemble(), b"$4=,^O>-")
+
+ def test_assign(self):
+ e = EBPF()
+ e.r5 = 7
+ e.r6 = e.r3
+ self.assertEqual(e.opcodes,
+ [Instruction(0xb7, 5, 0, 0, 7),
+ Instruction(0xbf, 6, 3, 0, 0)])
+
+ def test_short(self):
+ e = EBPF()
+ e.s3 = 7
+ e.s4 = e.s1
+ e.s2 += 3
+ e.s5 += e.s6
+ self.assertEqual(e.opcodes,
+ [Instruction(0xb4, 3, 0, 0, 7),
+ Instruction(0xbc, 4, 1, 0, 0),
+ Instruction(opcode=4, dst=2, src=0, off=0, imm=3),
+ Instruction(opcode=0xc, dst=5, src=6, off=0, imm=0)])
+
+ def test_augassign(self):
+ e = EBPF()
+ e.r5 += 7
+ e.r3 += e.r6
+ e.r4 -= 3
+ e.r4 -= e.r7
+ e.r4 *= 3
+ e.r4 *= e.r7
+ e.r4 /= 3
+ e.r4 /= e.r7
+ e.r4 |= 3
+ e.r4 |= e.r7
+ e.r4 &= 3
+ e.r4 &= e.r7
+ e.r4 <<= 3
+ e.r4 <<= e.r7
+ e.r4 >>= 3
+ e.r4 >>= e.r7
+ e.r4 %= 3
+ e.r4 %= e.r7
+ e.r4 ^= 3
+ e.r4 ^= e.r7
+
+ self.assertEqual(e.opcodes,
+ [Instruction(opcode=7, dst=5, src=0, off=0, imm=7),
+ Instruction(opcode=15, dst=3, src=6, off=0, imm=0),
+ Instruction(opcode=0x17, dst=4, src=0, off=0, imm=3),
+ Instruction(opcode=0x1f, dst=4, src=7, off=0, imm=0),
+ Instruction(opcode=0x27, dst=4, src=0, off=0, imm=3),
+ Instruction(opcode=0x2f, dst=4, src=7, off=0, imm=0),
+ Instruction(opcode=0x37, dst=4, src=0, off=0, imm=3),
+ Instruction(opcode=0x3f, dst=4, src=7, off=0, imm=0),
+ Instruction(opcode=0x47, dst=4, src=0, off=0, imm=3),
+ Instruction(opcode=0x4f, dst=4, src=7, off=0, imm=0),
+ Instruction(opcode=0x57, dst=4, src=0, off=0, imm=3),
+ Instruction(opcode=0x5f, dst=4, src=7, off=0, imm=0),
+ Instruction(opcode=0x67, dst=4, src=0, off=0, imm=3),
+ Instruction(opcode=0x6f, dst=4, src=7, off=0, imm=0),
+ Instruction(opcode=0x77, dst=4, src=0, off=0, imm=3),
+ Instruction(opcode=0x7f, dst=4, src=7, off=0, imm=0),
+ Instruction(opcode=0x97, dst=4, src=0, off=0, imm=3),
+ Instruction(opcode=0x9f, dst=4, src=7, off=0, imm=0),
+ Instruction(opcode=0xa7, dst=4, src=0, off=0, imm=3),
+ Instruction(opcode=0xaf, dst=4, src=7, off=0, imm=0)])
+
+
+if __name__ == "__main__":
+ main()
--
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