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seL4/libsel4/tools/syscall_stub_gen.py

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#!/usr/bin/env python
#
# Copyright 2014, NICTA
#
# This software may be distributed and modified according to the terms of
# the BSD 2-Clause license. Note that NO WARRANTY is provided.
# See "LICENSE_BSD2.txt" for details.
#
# @TAG(NICTA_BSD)
#
#
# seL4 System Call Stub Generator
# ===============================
#
# 2009 David Greenaway
#
# This script generates system call stubs based on an XML specification of the
# objects that the kernel exports (and the methods those objects export).
#
# Previously, Magpie (an IDL compiler) was used to generate these stubs. As
# Magpie development progressed, support for a fixed ABI (i.e., the ABI
# implemented by the seL4 kernel) was lost, and support for generating
# alignment-safe code (required by platforms such as ARM) was also removed.
#
# This script is a stop-gap until these features can be restored in Magpie
# once again.
#
# The script has certain limitations:
#
# * It must be told the size of all types. This includes complex types
# such as structures.
#
# We generate code that will cause compilation to fail if we get any
# object's size wrong, which should help mitigate the number of bugs caused
# because of this script becoming out of date compared to the source files.
#
# * The word-size is fixed at 32 bits, and we may implicitly assume that
# sizeof(int) == sizeof(long) == 32.
#
# Though the constant 'WORD_SIZE_BITS' has been used throughout, there
# may be implicit assumptions hanging around causing things to fail.
#
# * The script has only been tested on the actual seL4 API XML description.
#
# No stress testing has taken place; there may be bugs if new and wonderful
# XML method descriptions are added.
#
import xml.dom.minidom
import optparse
# Number of bits in a standard word
WORD_SIZE_BITS = 32
# Maximum number of words that will be in a message.
MAX_MESSAGE_LENGTH = 32
MESSAGE_REGISTERS_FOR_ARCH = {
"arm": 4,
"ia32": 2,
}
class Type(object):
"""
This class represents a C type (such as an 'int', structure or
pointer.
"""
def __init__(self, name, size_bits, double_word=False, native_size_bits=None):
"""
Define a new type, named 'name' that is 'size_bits' bits
long.
"""
self.name = name
self.size_bits = size_bits
self.double_word = double_word
#
# Store the number of bits C will use for this type
# in its native unpacked form.
#
# Required for 'bool', for example, which only uses 1
# bit when packed, but 32 bits when unpacked.
#
if native_size_bits:
self.native_size_bits = native_size_bits
else:
self.native_size_bits = size_bits
def pass_by_reference(self):
return self.size_bits > WORD_SIZE_BITS and not self.double_word
def render_parameter_name(self, name):
"""
Return a string of C code that would be used in a function
parameter declaration.
"""
return "%s %s" % (self.name, name)
def pointer(self):
"""
Return a new Type class representing a pointer to this
object.
"""
return PointerType(self)
def c_expression(self, var_name, word_num=0):
"""
Return code for a C expression that gets word 'word_num'
of this type.
"""
assert word_num == 0
return "%s" % var_name
def double_word_expression(self, var_name, word_num):
assert(word_num == 0 or word_num == 1)
if word_num == 0:
return "(uint{0}_t) {1}".format(WORD_SIZE_BITS, var_name)
elif word_num == 1:
return "(uint{0}_t) ({1} >> {0})".format(WORD_SIZE_BITS, var_name)
class PointerType(Type):
"""
A pointer to a standard type.
"""
def __init__(self, base_type):
Type.__init__(self, base_type.name, WORD_SIZE_BITS)
self.base_type = base_type
def render_parameter_name(self, name):
return "%s *%s" % (self.name, name)
def c_expression(self, var_name, word_num=0):
assert word_num == 0
return "*%s" % var_name
def pointer(self):
raise NotImplementedError()
class CapType(Type):
"""
A type that is just a typedef of seL4_CPtr.
"""
def __init__(self, name):
Type.__init__(self, name, WORD_SIZE_BITS)
class StructType(Type):
"""
A C 'struct' definition.
"""
def __init__(self, name, size_bits):
Type.__init__(self, name, size_bits)
def c_expression(self, var_name, word_num, member_name):
assert word_num < self.size_bits / WORD_SIZE_BITS
# Multiword structure.
assert self.pass_by_reference()
return "%s->%s" % (var_name, member_name[word_num])
class BitFieldType(Type):
"""
A special C 'struct' generated by the bitfield generator
"""
def __init__(self, name, size_bits):
Type.__init__(self, name, size_bits)
def c_expression(self, var_name, word_num=0):
return "%s.words[%d]" % (var_name, word_num)
class Parameter(object):
def __init__(self, name, type):
self.name = name
self.type = type
#
# Return the size (in bits) of a particular type.
#
types = [
# Simple Types
Type("uint8_t", 8),
Type("uint16_t", 16),
Type("uint32_t", 32),
Type("uint64_t", 64, double_word=True),
Type("int", WORD_SIZE_BITS),
Type("bool", 1, native_size_bits=8),
Type("seL4_Word", WORD_SIZE_BITS),
Type("seL4_CapRights", WORD_SIZE_BITS),
# seL4 Structures
BitFieldType("seL4_CapData_t", WORD_SIZE_BITS),
# Object types
CapType("seL4_CPtr"),
CapType("seL4_CNode"),
CapType("seL4_IRQHandler"),
CapType("seL4_IRQControl"),
CapType("seL4_TCB"),
CapType("seL4_Untyped"),
CapType("seL4_DomainSet"),
]
#
# Arch-specific types.
#
arch_types = {
"arm" : [
Type("seL4_ARM_VMAttributes", WORD_SIZE_BITS),
CapType("seL4_ARM_Page"),
CapType("seL4_ARM_PageTable"),
CapType("seL4_ARM_PageDirectory"),
CapType("seL4_ARM_ASIDControl"),
CapType("seL4_ARM_ASIDPool"),
StructType("seL4_UserContext", WORD_SIZE_BITS * 17),
],
"ia32" : [
Type("seL4_IA32_VMAttributes", WORD_SIZE_BITS),
CapType("seL4_IA32_ASIDControl"),
CapType("seL4_IA32_ASIDPool"),
CapType("seL4_IA32_IOSpace"),
CapType("seL4_IA32_IOPort"),
CapType("seL4_IA32_Page"),
CapType("seL4_IA32_PageDirectory"),
CapType("seL4_IA32_PageTable"),
CapType("seL4_IA32_IOPageTable"),
StructType("seL4_UserContext", WORD_SIZE_BITS * 13),
]
}
# Retrieve a member list for a given struct type
def struct_members(type, structs):
members = [member for struct_name, member in structs if struct_name == type.name]
assert len(members) == 1
return members[0]
# Keep increasing the given number 'x' until 'x % a == 0'.
def align_up(x, a):
if x % a == 0:
return x
return x + a - (x % a)
def get_parameter_positions(parameters):
"""
Determine where each parameter should be packed in the generated message.
We generate a list of:
(param_name, param_type, first_bit, num_bits)
tuples.
We guarantee that either (num_words == 1) or (bit_offset == 0).
"""
words_used = 0
bits_used = 0
results = []
for param in parameters:
# How big are we?
type_size = param.type.size_bits
# We need everything to be a power of two, or word sized.
assert ((type_size & (type_size - 1)) == 0) or (type_size % WORD_SIZE_BITS == 0)
# Align up to our own size, or the next word. (Whichever is smaller)
bits_used = align_up(bits_used, min(type_size, WORD_SIZE_BITS))
# Place ourself.
results.append((param, bits_used, type_size))
bits_used += type_size
return results
def generate_param_list(input_params, output_params):
# Generate parameters
params = []
for param in input_params:
if not param.type.pass_by_reference():
params.append(param.type.render_parameter_name(param.name))
else:
params.append(param.type.pointer().render_parameter_name(param.name))
for param in output_params:
if param.type.pass_by_reference():
params.append(param.type.pointer().render_parameter_name(param.name))
return ", ".join(params)
def generate_marshal_expressions(params, num_mrs, structs):
"""
Generate marshalling expressions for the given set of inputs.
We return a list of expressions; one expression per word required
to marshal all the inputs.
"""
def generate_param_code(param, first_bit, num_bits, word_array):
"""
Generate code to marshal the given parameter into the correct
location in the message.
'word_array' is an array of the final contents of the message.
word_array[k] contains what should be placed in the k'th message
register, and is an array of expressions that will (eventually)
be bitwise-or'ed into it.
"""
target_word = first_bit / WORD_SIZE_BITS
target_offset = first_bit % WORD_SIZE_BITS
# double word type
if param.type.double_word:
word_array[target_word].append(param.type.double_word_expression(param.name, 0))
word_array[target_word + 1].append(param.type.double_word_expression(param.name, 1))
return
# Single full word?
if num_bits == WORD_SIZE_BITS:
assert target_offset == 0
expr = param.type.c_expression(param.name);
word_array[target_word].append(expr)
return
# Part of a word?
if num_bits < WORD_SIZE_BITS:
expr = param.type.c_expression(param.name);
expr = "(%s & %#x)" % (expr, (1 << num_bits) - 1)
if target_offset:
expr = "(%s << %d)" % (expr, target_offset)
word_array[target_word].append(expr)
return
# Multiword array
assert target_offset == 0
num_words = num_bits / WORD_SIZE_BITS
for i in range(num_words):
expr = param.type.c_expression(param.name, i, struct_members(param.type, structs));
word_array[target_word + i].append(expr)
# Get their marshalling positions
positions = get_parameter_positions(params)
# Generate marshal code.
words = [[] for _ in range(num_mrs, MAX_MESSAGE_LENGTH)]
for (param, first_bit, num_bits) in positions:
generate_param_code(param, first_bit, num_bits, words)
# Return list of expressions.
return [" | ".join(x) for x in words if len(x) > 0]
def generate_unmarshal_expressions(params):
"""
Generate unmarshalling expressions for the given set of outputs.
We return a list of list of expressions; one list per variable, containing
expressions for the words in it that must be unmarshalled. The expressions
will have tokens of the form:
"%(w0)s"
in them, indicating a read from a word in the message.
"""
def unmarshal_single_param(first_bit, num_bits):
"""
Unmarshal a single parameter.
"""
first_word = first_bit / WORD_SIZE_BITS
bit_offset = first_bit % WORD_SIZE_BITS
# Multiword type?
if num_bits > WORD_SIZE_BITS:
result = []
for x in range(num_bits / WORD_SIZE_BITS):
result.append("%%(w%d)s" % (x + first_word))
return result
# Otherwise, bit packed.
if num_bits == WORD_SIZE_BITS:
return ["%%(w%d)s" % first_word]
elif bit_offset == 0:
return ["(%%(w%d)s & %#x)" % (
first_word, (1 << num_bits) - 1)]
else:
return ["(%%(w%d)s >> %d) & %#x" % (
first_word, bit_offset, (1 << num_bits) - 1)]
# Get their marshalling positions
positions = get_parameter_positions(params)
# Generate the unmarshal code.
results = []
for (param, first_bit, num_bits) in positions:
results.append((param, unmarshal_single_param(first_bit, num_bits)))
return results
def generate_result_struct(interface_name, method_name, output_params):
"""
Generate a structure definition to be returned by the system call stubs to
the user.
We have a few constraints:
* We always need an 'error' output parameter, even though it won't
appear in the list 'output_params' given to us.
* Output parameters may be marked as 'pass_by_reference', indicating
that we only ever see pointers to the item.
If no structure is needed (i.e., we just return an error code), we return
'None'.
"""
# Do we actually need a structure?
if len([x for x in output_params if not x.type.pass_by_reference()]) == 0:
return None
#
# Generate the structure:
#
# struct seL4_CNode_Copy {
# int error;
# seL4_Word foo;
# };
# typedef struct seL4_CNode_Copy seL4_CNode_Copy_t;
#
result = []
result.append("struct %s_%s {" % (interface_name, method_name))
result.append("\tint error;")
for i in output_params:
if not i.type.pass_by_reference():
result.append("\t%s;" % i.type.render_parameter_name(i.name))
result.append("};")
result.append("typedef struct %s_%s %s_%s_t;" % (
(interface_name, method_name, interface_name, method_name)))
result.append("")
return "\n".join(result)
def generate_stub(arch, interface_name, method_name, method_id, input_params, output_params, structs, use_only_ipc_buffer):
result = []
if use_only_ipc_buffer:
num_mrs = 0
else:
num_mrs = MESSAGE_REGISTERS_FOR_ARCH[arch]
# Split out cap parameters and standard parameters
standard_params = []
cap_params = []
for x in input_params:
if isinstance(x.type, CapType):
cap_params.append(x)
else:
standard_params.append(x)
# Determine if we are returning a structure, or just the error code.
returning_struct = False
results_structure = generate_result_struct(interface_name, method_name, output_params)
if results_structure:
return_type = "%s_%s_t" % (interface_name, method_name)
returning_struct = True
else:
return_type = "int"
#
# Print function header.
#
# static inline int
# seL4_Untyped_Retype(...)
# {
#
result.append("static inline %s" % return_type)
result.append("%s_%s(%s)" % (interface_name, method_name,
generate_param_list(input_params, output_params)))
result.append("{")
#
# Get a list of expressions for our caps and inputs.
#
input_expressions = generate_marshal_expressions(standard_params, num_mrs, structs)
cap_expressions = [x.name for x in cap_params]
service_cap = cap_expressions[0]
cap_expressions = cap_expressions[1:]
#
# Compute how many words the inputs and output will require.
#
input_param_words = len(input_expressions)
output_param_words = sum([p.type.size_bits for p in output_params]) / WORD_SIZE_BITS
#
# Setup variables we will need.
#
if returning_struct:
result.append("\t%s result;" % return_type)
result.append("\tseL4_MessageInfo_t tag = seL4_MessageInfo_new(%s, 0, %d, %d);" % (method_id, len(cap_expressions), len(input_expressions)))
result.append("\tseL4_MessageInfo_t output_tag;")
for i in range(min(num_mrs, max(input_param_words, output_param_words))):
result.append("\tseL4_Word mr%d;" % i)
result.append("")
#
# Copy capabilities.
#
# /* Setup input capabilities. */
# seL4_SetCap(i, cap);
#
if len(cap_expressions) > 0:
result.append("\t/* Setup input capabilities. */")
for i in range(len(cap_expressions)):
result.append("\tseL4_SetCap(%d, %s);" % (i, cap_expressions[i]))
result.append("")
#
# Copy in the inputs.
#
# /* Marshal input parameters. */
# seL4_SetMR(i, v);
# ...
#
if len(input_expressions) > 0:
result.append("\t/* Marshal input parameters. */")
for i in range(len(input_expressions)):
if i < num_mrs:
result.append("\tmr%d = %s;" % (i, input_expressions[i]))
else:
result.append("\tseL4_SetMR(%d, %s);" % (i, input_expressions[i]))
result.append("")
#
# Generate the call.
#
call_arguments = []
for i in range(num_mrs):
if i < max(input_param_words, output_param_words):
call_arguments.append("&mr%d" % i)
else:
call_arguments.append("NULL")
if use_only_ipc_buffer:
result.append("\t/* Perform the call. */")
result.append("\toutput_tag = seL4_Call(%s, tag);" % service_cap)
else:
result.append("\t/* Perform the call, passing in-register arguments directly. */")
result.append("\toutput_tag = seL4_CallWithMRs(%s, tag," % (service_cap))
result.append("\t\t%s);" % ', '.join(
[call_arguments[i] for i in range(num_mrs)]))
result.append("")
#
# Generate unmarshalling code.
#
if len(output_params) > 0:
result.append("\t/* Unmarshal result. */")
source_words = {}
for i in range(MAX_MESSAGE_LENGTH):
if i < num_mrs:
source_words["w%d" % i] = "mr%d" % i;
else:
source_words["w%d" % i] = "seL4_GetMR(%d)" % i;
unmashalled_params = generate_unmarshal_expressions(output_params)
for (param, words) in unmashalled_params:
if param.type.pass_by_reference():
members = struct_members(param.type, structs);
for i in range(len(words)):
result.append("\t%s->%s = %s;" % (param.name, members[i], words[i] % source_words))
else:
if param.type.double_word:
result.append("\tresult.%s = ((uint64_t)%s + ((uint64_t)%s << 32));" % (param.name, words[0] % source_words, words[1] % source_words))
else:
for word in words:
result.append("\tresult.%s = %s;" % (param.name, word % source_words))
result.append("")
# Return result
if returning_struct:
result.append("\tresult.error = seL4_MessageInfo_get_label(output_tag);")
result.append("\treturn result;")
else:
result.append("\treturn seL4_MessageInfo_get_label(output_tag);")
#
# }
#
result.append("}")
return "\n".join(result) + "\n"
def parse_xml_file(input_file, valid_types):
"""
Parse an XML file containing method definitions.
"""
# Create a dictionary of type name to type.
type_names = {}
for i in valid_types:
type_names[i.name] = i
# Parse the XML to generate method structures.
methods = []
structs = []
doc = xml.dom.minidom.parse(input_file)
for struct in doc.getElementsByTagName("struct"):
struct_members = []
struct_name = struct.getAttribute("name")
for members in struct.getElementsByTagName("member"):
member_name = members.getAttribute("name")
struct_members.append(member_name)
structs.append( (struct_name, struct_members) )
for interface in doc.getElementsByTagName("interface"):
interface_name = interface.getAttribute("name")
for method in interface.getElementsByTagName("method"):
method_name = method.getAttribute("name")
method_id = method.getAttribute("id")
#
# Get parameters.
#
# We always have an implicit cap parameter.
#
input_params = [Parameter("service", type_names[interface_name])]
output_params = []
for param in method.getElementsByTagName("param"):
param_name = param.getAttribute("name")
param_type = type_names.get(param.getAttribute("type"))
if not param_type:
raise Exception("Unknown type '%s'." % (param.getAttribute("type")))
param_dir = param.getAttribute("dir")
assert (param_dir == "in") or (param_dir == "out")
if (param_dir == "in"):
input_params.append(Parameter(param_name, param_type))
else:
output_params.append(Parameter(param_name, param_type))
methods.append((interface_name, method_name, method_id, input_params, output_params))
return (methods, structs)
def generate_stub_file(arch, input_files, output_file, use_only_ipc_buffer):
"""
Generate a header file containing system call stubs for seL4.
"""
result = []
# Ensure architecture looks sane.
if not arch in arch_types.keys():
raise Exception("Invalid architecture. Expected %s.",
" or ".join(arch_types.keys()))
# Parse XML
methods = []
structs = []
for file in input_files:
method, struct = parse_xml_file(file, types + arch_types[arch])
methods += method
structs += struct
# Print header.
result.append("""
/*
* Automatically generated system call stubs.
*/
#ifndef __LIBSEL4_SEL4_CLIENT_H
#define __LIBSEL4_SEL4_CLIENT_H
#include <stddef.h>
#include <stdbool.h>
#include <stdint.h>
#include "sel4/types.h"
#include "sel4/invocation.h"
#include "sel4/arch/functions.h"
#include "sel4/arch/syscalls.h"
""");
#
# Emit code to ensure that all of our type sizes are consistent with
# the compiler's.
#
result.append("""
/*
* The following code generates a compile-time error if the system call
* stub generator has an incorrect understanding of how large a type is.
*
* If you receive a compile-time error here, you will need to adjust
* the type information in the stub generator.
*/
#define assert_size_correct(type, expected_bytes) \\
typedef unsigned long __type_##type##_size_incorrect[ \\
(sizeof(type) == expected_bytes) ? 1 : -1]
""")
for x in types + arch_types[arch]:
result.append("assert_size_correct(%s, %d);" % (x.name, x.native_size_bits / 8))
result.append("")
#
# Generate structures needed to return results back to the user.
#
# We can not use pass-by-reference (except for really large objects), as
# the verification framework does not support them.
#
result.append("/*")
result.append(" * Return types for generated methods.")
result.append(" */")
for (interface_name, method_name, _, _, output_params) in methods:
results_structure = generate_result_struct(interface_name, method_name, output_params)
if results_structure:
result.append(results_structure)
#
# Generate the actual stub code.
#
result.append("/*")
result.append(" * Generated stubs.")
result.append(" */")
for (interface_name, method_name, method_id, inputs, outputs) in methods:
result.append(generate_stub(arch, interface_name, method_name,
method_id, inputs, outputs, structs, use_only_ipc_buffer))
# Print footer.
result.append("#endif /* __LIBSEL4_SEL4_CLIENT_H */")
result.append("")
# Write the output
output = open(output_file, "w")
output.write("\n".join(result))
output.close()
def main():
#
# Read command line arguments.
#
parser = optparse.OptionParser(
usage = "usage: %prog -a <arch> [-o <ouput file] <input XML> [<input XML> ...]")
parser.add_option("-a", "--arch",
dest="arch", help="Architecture to generate stubs for.")
parser.add_option("-o", "--output",
dest="output", help="Output file to write stub to.")
parser.add_option("-b", "--buffer", action="store_true",
help="Use IPC buffer exclusively (i.e. do not pass syscall "
"arguments by registers).")
(options, args) = parser.parse_args()
# Validate arguments
if len(args) < 1:
parser.error("Require at least one input file.")
if not options.arch:
parser.error("Require an architecture to be specified.")
if not options.output:
options.output = "/dev/stdout"
input_files = args
# Generate the stubs.
generate_stub_file(options.arch, input_files, options.output, options.buffer)
main()
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