upload android base code part3

android/bionic/libc/tools/genseccomp.py

@@ -0,0 +1,238 @@
+#!/usr/bin/env python
+import collections
+import os
+import textwrap
+from gensyscalls import SysCallsTxtParser
+from subprocess import Popen, PIPE
+
+
+BPF_JGE = "BPF_JUMP(BPF_JMP|BPF_JGE|BPF_K, {0}, {1}, {2})"
+BPF_ALLOW = "BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW)"
+
+
+class SyscallRange(object):
+  def __init__(self, name, value):
+    self.names = [name]
+    self.begin = value
+    self.end = self.begin + 1
+
+  def __str__(self):
+    return "(%s, %s, %s)" % (self.begin, self.end, self.names)
+
+  def add(self, name, value):
+    if value != self.end:
+      raise ValueError
+    self.end += 1
+    self.names.append(name)
+
+
+def get_names(syscall_files, architecture):
+  syscall_lists = []
+  for syscall_file in syscall_files:
+    parser = SysCallsTxtParser()
+    parser.parse_open_file(syscall_file)
+    syscall_lists.append(parser.syscalls)
+
+  bionic, whitelist, blacklist = syscall_lists[0], syscall_lists[1], syscall_lists[2]
+  for x in blacklist:
+    if not x in bionic:
+      raise RuntimeError("Blacklist item not in bionic - aborting " + str(x))
+
+    if x in whitelist:
+      raise RuntimeError("Blacklist item in whitelist - aborting " + str(x))
+
+  bionic_minus_blacklist = [x for x in bionic if x not in blacklist]
+  syscalls = bionic_minus_blacklist + whitelist
+
+  # Select only elements matching required architecture
+  syscalls = [x for x in syscalls if architecture in x and x[architecture]]
+
+  # We only want the name
+  names = [x["name"] for x in syscalls]
+
+  # Check for duplicates
+  dups = [name for name, count in collections.Counter(names).items() if count > 1]
+
+  # x86 has duplicate socketcall entries, so hard code for this
+  if architecture == "x86":
+    dups.remove("socketcall")
+
+  if len(dups) > 0:
+    raise RuntimeError("Duplicate entries found - aborting " + str(dups))
+
+  # Remove remaining duplicates
+  return list(set(names))
+
+
+def convert_names_to_NRs(names, header_dir, extra_switches):
+  # Run preprocessor over the __NR_syscall symbols, including unistd.h,
+  # to get the actual numbers
+  prefix = "__SECCOMP_"  # prefix to ensure no name collisions
+  cpp = Popen(["../../prebuilts/clang/host/linux-x86/clang-stable/bin/clang",
+               "-E", "-nostdinc", "-I" + header_dir, "-Ikernel/uapi/"]
+               + extra_switches
+               + ["-"],
+              stdin=PIPE, stdout=PIPE)
+  cpp.stdin.write("#include <asm/unistd.h>\n")
+  for name in names:
+    # In SYSCALLS.TXT, there are two arm-specific syscalls whose names start
+    # with __ARM__NR_. These we must simply write out as is.
+    if not name.startswith("__ARM_NR_"):
+      cpp.stdin.write(prefix + name + ", __NR_" + name + "\n")
+    else:
+      cpp.stdin.write(prefix + name + ", " + name + "\n")
+  content = cpp.communicate()[0].split("\n")
+
+  # The input is now the preprocessed source file. This will contain a lot
+  # of junk from the preprocessor, but our lines will be in the format:
+  #
+  #     __SECCOMP_${NAME}, (0 + value)
+
+  syscalls = []
+  for line in content:
+    if not line.startswith(prefix):
+      continue
+
+    # We might pick up extra whitespace during preprocessing, so best to strip.
+    name, value = [w.strip() for w in line.split(",")]
+    name = name[len(prefix):]
+
+    # Note that some of the numbers were expressed as base + offset, so we
+    # need to eval, not just int
+    value = eval(value)
+    syscalls.append((name, value))
+
+  return syscalls
+
+
+def convert_NRs_to_ranges(syscalls):
+  # Sort the values so we convert to ranges and binary chop
+  syscalls = sorted(syscalls, lambda x, y: cmp(x[1], y[1]))
+
+  # Turn into a list of ranges. Keep the names for the comments
+  ranges = []
+  for name, value in syscalls:
+    if not ranges:
+      ranges.append(SyscallRange(name, value))
+      continue
+
+    last_range = ranges[-1]
+    if last_range.end == value:
+      last_range.add(name, value)
+    else:
+      ranges.append(SyscallRange(name, value))
+  return ranges
+
+
+# Converts the sorted ranges of allowed syscalls to a binary tree bpf
+# For a single range, output a simple jump to {fail} or {allow}. We can't set
+# the jump ranges yet, since we don't know the size of the filter, so use a
+# placeholder
+# For multiple ranges, split into two, convert the two halves and output a jump
+# to the correct half
+def convert_to_intermediate_bpf(ranges):
+  if len(ranges) == 1:
+    # We will replace {fail} and {allow} with appropriate range jumps later
+    return [BPF_JGE.format(ranges[0].end, "{fail}", "{allow}") +
+            ", //" + "|".join(ranges[0].names)]
+  else:
+    half = (len(ranges) + 1) / 2
+    first = convert_to_intermediate_bpf(ranges[:half])
+    second = convert_to_intermediate_bpf(ranges[half:])
+    jump = [BPF_JGE.format(ranges[half].begin, len(first), 0) + ","]
+    return jump + first + second
+
+
+def convert_ranges_to_bpf(ranges):
+  bpf = convert_to_intermediate_bpf(ranges)
+
+  # Now we know the size of the tree, we can substitute the {fail} and {allow}
+  # placeholders
+  for i, statement in enumerate(bpf):
+    # Replace placeholder with
+    # "distance to jump to fail, distance to jump to allow"
+    # We will add a kill statement and an allow statement after the tree
+    # With bpfs jmp 0 means the next statement, so the distance to the end is
+    # len(bpf) - i - 1, which is where we will put the kill statement, and
+    # then the statement after that is the allow statement
+    if "{fail}" in statement and "{allow}" in statement:
+      bpf[i] = statement.format(fail=str(len(bpf) - i),
+                                allow=str(len(bpf) - i - 1))
+
+
+  # Add the allow calls at the end. If the syscall is not matched, we will
+  # continue. This allows the user to choose to match further syscalls, and
+  # also to choose the action when we want to block
+  bpf.append(BPF_ALLOW + ",")
+
+  # Add check that we aren't off the bottom of the syscalls
+  bpf.insert(0, BPF_JGE.format(ranges[0].begin, 0, str(len(bpf))) + ',')
+  return bpf
+
+
+def convert_bpf_to_output(bpf, architecture):
+  header = textwrap.dedent("""\
+    // Autogenerated file - edit at your peril!!
+
+    #include <linux/filter.h>
+    #include <errno.h>
+
+    #include "seccomp_bpfs.h"
+    const sock_filter {architecture}_filter[] = {{
+    """).format(architecture=architecture)
+
+  footer = textwrap.dedent("""\
+
+    }};
+
+    const size_t {architecture}_filter_size = sizeof({architecture}_filter) / sizeof(struct sock_filter);
+    """).format(architecture=architecture)
+  return header + "\n".join(bpf) + footer
+
+
+def construct_bpf(syscall_files, architecture, header_dir, extra_switches):
+  names = get_names(syscall_files, architecture)
+  syscalls = convert_names_to_NRs(names, header_dir, extra_switches)
+  ranges = convert_NRs_to_ranges(syscalls)
+  bpf = convert_ranges_to_bpf(ranges)
+  return convert_bpf_to_output(bpf, architecture)
+
+
+ANDROID_SYSCALL_FILES = ["SYSCALLS.TXT",
+                         "SECCOMP_WHITELIST.TXT",
+                         "SECCOMP_BLACKLIST.TXT"]
+
+
+POLICY_CONFIGS = [("arm", "kernel/uapi/asm-arm", []),
+                  ("arm64", "kernel/uapi/asm-arm64", []),
+                  ("x86", "kernel/uapi/asm-x86", ["-D__i386__"]),
+                  ("x86_64", "kernel/uapi/asm-x86", []),
+                  ("mips", "kernel/uapi/asm-mips", ["-D_MIPS_SIM=_MIPS_SIM_ABI32"]),
+                  ("mips64", "kernel/uapi/asm-mips", ["-D_MIPS_SIM=_MIPS_SIM_ABI64"])]
+
+
+def set_dir():
+  # Set working directory for predictable results
+  os.chdir(os.path.join(os.environ["ANDROID_BUILD_TOP"], "bionic/libc"))
+
+
+def main():
+  set_dir()
+  for arch, header_path, switches in POLICY_CONFIGS:
+    files = [open(filename) for filename in ANDROID_SYSCALL_FILES]
+    output = construct_bpf(files, arch, header_path, switches)
+
+    # And output policy
+    existing = ""
+    output_path = "seccomp/{}_policy.cpp".format(arch)
+    if os.path.isfile(output_path):
+      existing = open(output_path).read()
+    if output == existing:
+      print "File " + output_path + " not changed."
+    else:
+      with open(output_path, "w") as output_file:
+        output_file.write(output)
+      print "Generated file " + output_path
+
+if __name__ == "__main__":
+  main()