chromium/sandbox/linux/seccomp-bpf/syscall.cc

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/351564777): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif

#include "sandbox/linux/seccomp-bpf/syscall.h"

#include <errno.h>
#include <stdint.h>

#include <ostream>

#include "base/check_op.h"
#include "build/build_config.h"
#include "sandbox/linux/bpf_dsl/seccomp_macros.h"

namespace sandbox {

namespace {

#if defined(ARCH_CPU_X86_FAMILY) || defined(ARCH_CPU_ARM_FAMILY) || \
    defined(ARCH_CPU_MIPS_FAMILY)
// Number that's not currently used by any Linux kernel ABIs.
const int kInvalidSyscallNumber = …;
#else
#error Unrecognized architecture
#endif

asm …;  // asm

#if defined(__x86_64__)
extern "C" {
intptr_t SyscallAsm(intptr_t nr, const intptr_t args[6]);
}
#elif defined(__mips__)
extern "C" {
intptr_t SyscallAsm(intptr_t nr, const intptr_t args[8]);
}
#endif

}  // namespace

intptr_t Syscall::InvalidCall() { … }

intptr_t Syscall::Call(int nr,
                       intptr_t p0,
                       intptr_t p1,
                       intptr_t p2,
                       intptr_t p3,
                       intptr_t p4,
                       intptr_t p5,
                       intptr_t p6,
                       intptr_t p7) { … }

void Syscall::PutValueInUcontext(intptr_t ret_val, ucontext_t* ctx) { … }

#if defined(__mips__)
intptr_t Syscall::SandboxSyscallRaw(int nr,
                                    const intptr_t* args,
                                    intptr_t* err_ret) {
  register intptr_t ret __asm__("v0") = nr;
  register intptr_t syscallasm __asm__("t9") = (intptr_t) &SyscallAsm;
  // a3 register becomes non zero on error.
  register intptr_t err_stat __asm__("a3") = 0;
  {
    register const intptr_t* data __asm__("a0") = args;
    asm volatile(
        "jalr $t9\n"
        " nop\n"
        : "=r"(ret), "=r"(err_stat)
        : "0"(ret),
          "r"(data),
          "r"(syscallasm)
          // a2 is in the clober list so inline assembly can not change its
          // value.
        : "memory", "ra", "a2");
  }

  // Set an error status so it can be used outside of this function
  *err_ret = err_stat;

  return ret;
}
#endif  // defined(__mips__)

}  // namespace sandbox