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zephyr/scripts/gen_syscalls.py
Andy Ross 6564974bae userspace: Support for split 64 bit arguments 
System call arguments, at the arch layer, are single words.  So
passing wider values requires splitting them into two registers at
call time.  This gets even more complicated for values (e.g
k_timeout_t) that may have different sizes depending on configuration.
This patch adds a feature to gen_syscalls.py to detect functions with
wide arguments and automatically generates code to split/unsplit them.

Unfortunately the current scheme of Z_SYSCALL_DECLARE_* macros won't
work with functions like this, because for N arguments (our current
maximum N is 10) there are 2^N possible configurations of argument
widths.  So this generates the complete functions for each handler and
wrapper, effectively doing in python what was originally done in the
preprocessor.

Another complexity is that traditional the z_hdlr_*() function for a
system call has taken the raw list of word arguments, which does not
work when some of those arguments must be 64 bit types.  So instead of
using a single Z_SYSCALL_HANDLER macro, this splits the job of
z_hdlr_*() into two steps: An automatically-generated unmarshalling
function, z_mrsh_*(), which then calls a user-supplied verification
function z_vrfy_*().  The verification function is typesafe, and is a
simple C function with exactly the same argument and return signature
as the syscall impl function.  It is also not responsible for
validating the pointers to the extra parameter array or a wide return
value, that code gets automatically generated.

This commit includes new vrfy/msrh handling for all syscalls invoked
during CI runs.  Future commits will port the less testable code.

Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
2019-09-12 11:31:50 +08:00

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#!/usr/bin/env python3
#
# Copyright (c) 2017 Intel Corporation
#
# SPDX-License-Identifier: Apache-2.0
"""
Script to generate system call invocation macros
This script parses the system call metadata JSON file emitted by
parse_syscalls.py to create several files:
- A file containing weak aliases of any potentially unimplemented system calls,
as well as the system call dispatch table, which maps system call type IDs
to their handler functions.
- A header file defing the system call type IDs, as well as function
prototypes for all system call handler functions.
- A directory containing header files. Each header corresponds to a header
that was identified as containing system call declarations. These
generated headers contain the inline invocation functions for each system
call in that header.
"""
import sys
import re
import argparse
import os
import json
types64 = ["s64_t", "u64_t"]
# The kernel linkage is complicated. These functions from
# userspace_handlers.c are present in the kernel .a library after
# userspace.c, which contains the weak fallbacks defined here. So the
# linker finds the weak one first and stops searching, and thus won't
# see the real implementation which should override. Yet changing the
# order runs afoul of a comment in CMakeLists.txt that the order is
# critical. These are core syscalls that won't ever be unconfigured,
# just disable the fallback mechanism as a simple workaround.
noweak = set(["z_mrsh_k_object_release",
"z_mrsh_k_object_access_grant",
"z_mrsh_k_object_alloc"])
table_template = """/* auto-generated by gen_syscalls.py, don't edit */
/* Weak handler functions that get replaced by the real ones unless a system
* call is not implemented due to kernel configuration.
*/
%s
const _k_syscall_handler_t _k_syscall_table[K_SYSCALL_LIMIT] = {
\t%s
};
"""
list_template = """
/* auto-generated by gen_syscalls.py, don't edit */
#ifndef ZEPHYR_SYSCALL_LIST_H
#define ZEPHYR_SYSCALL_LIST_H
%s
#ifndef _ASMLANGUAGE
#include <zephyr/types.h>
#endif /* _ASMLANGUAGE */
#endif /* ZEPHYR_SYSCALL_LIST_H */
"""
syscall_template = """
/* auto-generated by gen_syscalls.py, don't edit */
%s
#ifndef _ASMLANGUAGE
#include <syscall_list.h>
#include <syscall_macros.h>
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wstrict-aliasing"
#ifdef __cplusplus
extern "C" {
#endif
%s
#ifdef __cplusplus
}
#endif
#pragma GCC diagnostic pop
#endif
#endif /* include guard */
"""
handler_template = """
extern u32_t z_hdlr_%s(u32_t arg1, u32_t arg2, u32_t arg3,
u32_t arg4, u32_t arg5, u32_t arg6, void *ssf);
"""
weak_template = """
__weak ALIAS_OF(handler_no_syscall)
u32_t %s(u32_t arg1, u32_t arg2, u32_t arg3,
u32_t arg4, u32_t arg5, u32_t arg6, void *ssf);
"""
typename_regex = re.compile(r'(.*?)([A-Za-z0-9_]+)$')
class SyscallParseException(Exception):
pass
def typename_split(item):
if "[" in item:
raise SyscallParseException(
"Please pass arrays to syscalls as pointers, unable to process '%s'" %
item)
if "(" in item:
raise SyscallParseException(
"Please use typedefs for function pointers")
mo = typename_regex.match(item)
if not mo:
raise SyscallParseException("Malformed system call invocation")
m = mo.groups()
return (m[0].strip(), m[1])
def need_split(argtype):
return argtype in types64
# Note: "lo" and "hi" are named in little endian conventions,
# but it doesn't matter as long as they are consistently
# generated.
def union_decl(type):
return "union { struct { u32_t lo, hi; } split; %s val; }" % type
def wrapper_defs(func_name, func_type, args):
ret64 = func_type in types64
mrsh_args = [] # List of rvalue expressions for the marshalled invocation
split_args = []
nsplit = 0
for i, argrec in enumerate(args):
(argtype, argname) = argrec
if need_split(argtype):
split_args.append((argtype, argname))
mrsh_args.append("parm%d.split.lo" % nsplit)
mrsh_args.append("parm%d.split.hi" % nsplit)
nsplit += 1
else:
mrsh_args.append("*(u32_t *)&" + argname)
if ret64:
mrsh_args.append("(u32_t)&ret64")
decl_arglist = ", ".join([" ".join(argrec) for argrec in args])
wrap = "extern %s z_impl_%s(%s);\n" % (func_type, func_name, decl_arglist)
wrap += "static inline %s %s(%s)\n" % (func_type, func_name, decl_arglist)
wrap += "{\n"
wrap += "#ifdef CONFIG_USERSPACE\n"
wrap += ("\t" + "u64_t ret64;\n") if ret64 else ""
wrap += "\t" + "if (z_syscall_trap()) {\n"
for parmnum, rec in enumerate(split_args):
(argtype, argname) = rec
wrap += "\t\t%s parm%d;\n" % (union_decl(argtype), parmnum)
wrap += "\t\t" + "parm%d.val = %s;\n" % (parmnum, argname)
if len(mrsh_args) > 6:
wrap += "\t\t" + "u32_t more[] = {\n"
wrap += "\t\t\t" + (",\n\t\t\t".join(mrsh_args[5:])) + "\n"
wrap += "\t\t" + "};\n"
mrsh_args[5:] = ["(u32_t) &more"]
syscall_id = "K_SYSCALL_" + func_name.upper()
invoke = ("z_arch_syscall_invoke%d(%s)"
% (len(mrsh_args),
", ".join(mrsh_args + [syscall_id])))
if ret64:
wrap += "\t\t" + "(void)%s;\n" % invoke
wrap += "\t\t" + "return (%s)ret64;\n" % func_type
elif func_type == "void":
wrap += "\t\t" + "%s;\n" % invoke
wrap += "\t\t" + "return;\n";
else:
wrap += "\t\t" + "return (%s) %s;\n" % (func_type, invoke)
wrap += "\t" + "}\n"
wrap += "#endif\n"
# Otherwise fall through to direct invocation of the impl func.
# Note the compiler barrier: that is required to prevent code from
# the impl call from being hoisted above the check for user
# context.
impl_arglist = ", ".join([argrec[1] for argrec in args])
impl_call = "z_impl_%s(%s)" % (func_name, impl_arglist)
wrap += "\t" + "compiler_barrier();\n"
wrap += "\t" + "%s%s;\n" % ("return " if func_type != "void" else "",
impl_call)
wrap += "}\n"
return wrap
# Returns an expression for the specified (zero-indexed!) marshalled
# parameter to a syscall, with handling for a final "more" parameter.
def mrsh_rval(mrsh_num, total):
if mrsh_num < 5 or total <= 6:
return "arg%d" % mrsh_num
else:
return "(((u32_t *)more)[%d])" % (mrsh_num - 5)
def marshall_defs(func_name, func_type, args):
mrsh_name = "z_mrsh_" + func_name
nmrsh = 0 # number of marshalled u32_t parameter
vrfy_parms = [] # list of (arg_num, mrsh_or_parm_num, bool_is_split)
split_parms = [] # list of a (arg_num, mrsh_num) for each split
for i, argrec in enumerate(args):
(argtype, argname) = argrec
if need_split(argtype):
vrfy_parms.append((i, len(split_parms), True))
split_parms.append((i, nmrsh))
nmrsh += 2
else:
vrfy_parms.append((i, nmrsh, False))
nmrsh += 1
# Final argument for a 64 bit return value?
if func_type in types64:
nmrsh += 1
decl_arglist = ", ".join([" ".join(argrec) for argrec in args])
mrsh = "extern %s z_vrfy_%s(%s);\n" % (func_type, func_name, decl_arglist)
mrsh += "u32_t %s(u32_t arg0, u32_t arg1, u32_t arg2,\n" % mrsh_name
if nmrsh <= 6:
mrsh += "\t\t" + "u32_t arg3, u32_t arg4, u32_t arg5, void *ssf)\n";
else:
mrsh += "\t\t" + "u32_t arg3, u32_t arg4, void *more, void *ssf)\n";
mrsh += "{\n"
mrsh += "\t" + "_current_cpu->syscall_frame = ssf;\n";
for unused_arg in range(nmrsh, 6):
mrsh += "\t(void) arg%d;\t/* unused */\n" % unused_arg
if nmrsh > 6:
mrsh += ("\tZ_OOPS(Z_SYSCALL_MEMORY_READ(more, "
+ str(nmrsh - 6) + " * sizeof(u32_t)));\n")
for i, split_rec in enumerate(split_parms):
arg_num, mrsh_num = split_rec
arg_type = args[arg_num][0];
mrsh += "\t%s parm%d;\n" % (union_decl(arg_type), i);
mrsh += "\t" + "parm%d.split.lo = %s;\n" % (i, mrsh_rval(mrsh_num,
nmrsh))
mrsh += "\t" + "parm%d.split.hi = %s;\n" % (i, mrsh_rval(mrsh_num + 1,
nmrsh))
# Finally, invoke the verify function
out_args = []
for i, argn, is_split in vrfy_parms:
if is_split:
out_args.append("parm%d.val" % argn)
else:
out_args.append("*(%s*)&%s" % (args[i][0], mrsh_rval(argn, nmrsh)))
vrfy_call = "z_vrfy_%s(%s)\n" % (func_name, ", ".join(out_args))
if func_type == "void":
mrsh += "\t" + "%s;\n" % vrfy_call
mrsh += "\t" + "return 0;\n"
else:
mrsh += "\t" + "%s ret = %s;\n" % (func_type, vrfy_call)
if func_type in types64:
ptr = "((u64_t *)%s)" % mrsh_rval(nmrsh - 1, nmrsh)
mrsh += "\t" + "Z_OOPS(Z_SYSCALL_MEMORY_WRITE(%s, 8));\n" % ptr
mrsh += "\t" + "*%s = ret;\n" % ptr
mrsh += "\t" + "return 0;\n"
else:
mrsh += "\t" + "return (u32_t) ret;\n"
mrsh += "}\n"
return mrsh, mrsh_name
def analyze_fn(match_group):
func, args = match_group
try:
if args == "void":
args = []
else:
args = [typename_split(a.strip()) for a in args.split(",")]
func_type, func_name = typename_split(func)
except SyscallParseException:
sys.stderr.write("In declaration of %s\n" % func)
raise
sys_id = "K_SYSCALL_" + func_name.upper()
marshaller = None
marshaller, handler = marshall_defs(func_name, func_type, args)
invocation = wrapper_defs(func_name, func_type, args)
# Entry in _k_syscall_table
table_entry = "[%s] = %s" % (sys_id, handler)
return (handler, invocation, marshaller, sys_id, table_entry)
def parse_args():
global args
parser = argparse.ArgumentParser(
description=__doc__,
formatter_class=argparse.RawDescriptionHelpFormatter)
parser.add_argument("-i", "--json-file", required=True,
help="Read syscall information from json file")
parser.add_argument("-d", "--syscall-dispatch", required=True,
help="output C system call dispatch table file")
parser.add_argument("-l", "--syscall-list", required=True,
help="output C system call list header")
parser.add_argument("-o", "--base-output", required=True,
help="Base output directory for syscall macro headers")
parser.add_argument("-s", "--split-type", action="append",
help="A long type that must be split/marshalled")
args = parser.parse_args()
def main():
parse_args()
if args.split_type != None:
for t in args.split_type:
types64.append(t)
with open(args.json_file, 'r') as fd:
syscalls = json.load(fd)
invocations = {}
mrsh_defs = {}
mrsh_includes = {}
ids = []
table_entries = []
handlers = []
for match_group, fn in syscalls:
handler, inv, mrsh, sys_id, entry = analyze_fn(match_group)
if fn not in invocations:
invocations[fn] = []
invocations[fn].append(inv)
ids.append(sys_id)
table_entries.append(entry)
handlers.append(handler)
if mrsh:
syscall = typename_split(match_group[0])[1]
mrsh_defs[syscall] = mrsh
mrsh_includes[syscall] = "#include <syscalls/%s>" % fn
with open(args.syscall_dispatch, "w") as fp:
table_entries.append("[K_SYSCALL_BAD] = handler_bad_syscall")
weak_defines = "".join([weak_template % name
for name in handlers
if not name in noweak])
# The "noweak" ones just get a regular declaration
weak_defines += "\n".join(["extern u32_t %s(u32_t arg1, u32_t arg2, u32_t arg3, u32_t arg4, u32_t arg5, u32_t arg6, void *ssf);"
% s for s in noweak])
fp.write(table_template % (weak_defines,
",\n\t".join(table_entries)))
# Listing header emitted to stdout
ids.sort()
ids.extend(["K_SYSCALL_BAD", "K_SYSCALL_LIMIT"])
ids_as_defines = ""
for i, item in enumerate(ids):
ids_as_defines += "#define {} {}\n".format(item, i)
with open(args.syscall_list, "w") as fp:
fp.write(list_template % ids_as_defines)
os.makedirs(args.base_output, exist_ok=True)
for fn, invo_list in invocations.items():
out_fn = os.path.join(args.base_output, fn)
ig = re.sub("[^a-zA-Z0-9]", "_", "Z_INCLUDE_SYSCALLS_" + fn).upper()
include_guard = "#ifndef %s\n#define %s\n" % (ig, ig)
header = syscall_template % (include_guard, "\n\n".join(invo_list))
with open(out_fn, "w") as fp:
fp.write(header)
# Likewise emit _mrsh.c files for syscall inclusion
for fn in mrsh_defs:
mrsh_fn = os.path.join(args.base_output, fn + "_mrsh.c")
with open(mrsh_fn, "w") as fp:
fp.write("/* auto-generated by gen_syscalls.py, don't edit */\n")
fp.write("#pragma GCC diagnostic push\n")
fp.write("#pragma GCC diagnostic ignored \"-Wstrict-aliasing\"\n")
fp.write(mrsh_includes[fn] + "\n")
fp.write("\n")
fp.write(mrsh_defs[fn] + "\n")
fp.write("#pragma GCC diagnostic pop\n")
if __name__ == "__main__":
main()
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