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<html devsite>
<head>
<title>Interface Requirements</title>
<meta name="project_path" value="/_project.yaml" />
<meta name="book_path" value="/_book.yaml" />
</head>
<body>
<!--
Copyright 2017 The Android Open Source Project
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You may obtain a copy of the License at
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distributed under the License is distributed on an "AS IS" BASIS,
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<p>This page describes a subset of the Linux kernel interfaces on which Android
relies to function properly. The presence and correctness of these interfaces is
tested as part of the <a href="/devices/tech/vts/index.html">Vendor Test Suite
(VTS)</a>. This subset will grow over time to contain a larger portion of
Android kernel interfaces.</p>
<h2 id="system-calls">System calls</h2>
<p>System calls are expected to provide the same signatures and semantics as in
the upstream Linux kernel.</p>
<p>ARM64 system calls required by bionic per
<code>bionic/libc/SYSCALLS.txt</code>:</p>
<table>
<tr>
<td class="devsite-click-to-copy">accept4, acct, adjtimex, bind, brk, capget, capset, chdir, chroot, clock_adjtime, clock_getres, clock_gettime, clock_nanosleep, clock_settime, close, connect, delete_module, dup3, dup, epoll_create1, epoll_ctl, epoll_pwait, eventfd2, execve, exit, exit_group, faccessat, fadvise64, fallocate, fchdir, fchmodat, fchmod, fchownat, fchown, fcntl, fdatasync, fgetxattr, flistxattr, flock, fremovexattr, fsetxattr, fstat, newfstatat, fstatfs, fsync, ftruncate, getcpu, getcwd, getdents64, getegid, geteuid, getgid, getgroups, getitimer, getpeername, getpgid, getpid, getppid, getpriority, getresgid, getresuid, getrlimit, getrusage, getsid, getsockname, getsockopt, gettimeofday, getuid, getxattr, init_module, inotify_add_watch, inotify_init1, inotify_rm_watch, ioctl, kill, syslog, lgetxattr, linkat, listen, listxattr, llistxattr, lremovexattr, lseek, lsetxattr, madvise, mincore, mkdirat, mknodat, mlockall, mlock, mmap, mount, mprotect, mremap, msync, munlockall, munlock, munmap, nanosleep, openat, personality, pipe2, ppoll, prctl, pread64, preadv, prlimit64, process_vm_readv, process_vm_writev, pselect6, ptrace, pwrite64, pwritev, quotactl, readahead, readlinkat, read, readv, reboot, recvfrom, recvmmsg, recvmsg, removexattr, renameat, rt_sigaction, rt_sigpending, rt_sigprocmask, rt_sigqueueinfo, rt_sigsuspend, rt_sigtimedwait, sched_getaffinity, sched_getparam, sched_get_priority_max, sched_get_priority_min, sched_getscheduler, sched_rr_get_interval, sched_setaffinity, sched_setparam, sched_setscheduler, sched_yield, sendfile, sendmmsg, sendmsg, sendto, setdomainname, setfsgid, setfsuid, setgid, setgroups, sethostname, setitimer, setns, setpgid, setpriority, setregid, setresgid, setresuid, setreuid, setrlimit, setsid, setsockopt, set_tid_address, settimeofday, setuid, setxattr, shutdown, sigaltstack, signalfd4, socketpair, socket, splice, statfs, swapoff, swapon, symlinkat, sync_file_range, sync, sysinfo, tee, tgkill, timer_create, timer_delete, timerfd_create, timerfd_gettime, timerfd_settime, timer_getoverrun, timer_gettime, timer_settime, times, truncate, umask, umount2, uname, unlinkat, unshare, utimensat, vmsplice, wait4, waitid, write, writev</td>
</tr></table>
<p>ARM32 system calls required by bionic per
<code>bionic/libc/SYSCALLS.txt</code>:</p>
<table>
<tr>
<td class="devsite-click-to-copy">accept4, acct, adjtimex, arm_fadvise64_64, bind, brk, cacheflush, capget, capset, chdir, chroot, clock_adjtime, clock_getres, clock_gettime, clock_nanosleep, clock_settime, close, connect, delete_module, dup3, dup, epoll_create1, epoll_ctl, epoll_pwait, eventfd2, execve, exit, exit_group, faccessat, fallocate, fchdir, fchmodat, fchmod, fchownat, fchown32, fcntl64, fdatasync, fgetxattr, flistxattr, flock, fremovexattr, fsetxattr, fstat64, fstatat64, fstatfs64, fsync, ftruncate64, getcpu, getcwd, getdents64, getegid32, geteuid32, getgid32, getgroups32, getitimer, getpeername, getpgid, getpid, getppid, getpriority, getresgid32, getresuid32, ugetrlimit, getrusage, getsid, getsockname, getsockopt, gettimeofday, getuid32, getxattr, init_module, inotify_add_watch, inotify_init1, inotify_rm_watch, ioctl, kill, syslog, lgetxattr, linkat, listen, listxattr, llistxattr, _llseek, lremovexattr, lseek, lsetxattr, madvise, mincore, mkdirat, mknodat, mlockall, mlock, mmap2, mount, mprotect, mremap, msync, munlockall, munlock, munmap, nanosleep, openat, personality, pipe2, ppoll, prctl, pread64, preadv, prlimit64, process_vm_readv, process_vm_writev, pselect6, ptrace, pwrite64, pwritev, quotactl, readahead, readlinkat, read, readv, reboot, recvfrom, recvmmsg, recvmsg, removexattr, renameat, rt_sigaction, rt_sigpending, rt_sigprocmask, rt_sigqueueinfo, rt_sigsuspend, rt_sigtimedwait, sched_getaffinity, sched_getparam, sched_get_priority_max, sched_get_priority_min, sched_getscheduler, sched_rr_get_interval, sched_setaffinity, sched_setparam, sched_setscheduler, sched_yield, sendfile64, sendfile, sendmmsg, sendmsg, sendto, setdomainname, setfsgid, setfsuid, setgid32, setgroups32, sethostname, setitimer, setns, setpgid, setpriority, setregid32, setresgid32, setresuid32, setreuid32, setrlimit, setsid, setsockopt, set_tid_address, settimeofday, set_tls, setuid32, setxattr, shutdown, sigaction, sigaltstack, signalfd4, socketpair, socket, splice, statfs64, swapoff, swapon, symlinkat, sync_file_range2, sync, sysinfo, tee, tgkill, timer_create, timer_delete, timerfd_create, timerfd_gettime, timerfd_settime, timer_getoverrun, timer_gettime, timer_settime, times, truncate64, truncate, umask, umount2, uname, unlinkat, unshare, utimensat, vmsplice, wait4, waitid, write, writev</td>
</tr></table>
<p>The system calls listed below are made by bypassing bionic:</p>
<table>
<tr>
<th style="width:20%">All Architectures</th>
<td>gettid, futex, clone, rt_sigreturn, rt_tgsigqueueinfo, restart_syscall,
getrandom, perf_event_open, syncfs, tkill, seccomp</td>
</tr>
<tr>
<th>arm</th>
<td>vfork, sigreturn, pipe, access, stat64, lstat64, open, getdents, eventfd,
epoll_wait, readlink, epoll_create, creat, unlink</td>
</tr>
<tr>
<th>arm64</th>
<td>pivot_root, ioprio_get, ioprio_set</td>
</tr>
</table>
<aside class="note"><strong>Note:</strong> x86 and x86_64 system calls will be
added in a future release.</aside>
<h3 id="prctl">prctl</h3>
<p>In addition to the upstream <code>prctl</code> operations for supported
kernel versions, Android relies on additional <code>prctl</code> operations, the
implementation of which can be found in the android-common kernel.</p>
<pre class="prettyprint">
PR_SET_TIMERSLACK_PID
PR_SET_VMA
</pre>
<h2 id="filesystems">Filesystems</h2>
<p>The Linux kernel exports interfaces via several filesystems. Android expects
these interfaces to communicate the same information, in the same format, and
provide the same semantics as in the upstream Linux kernel. For interfaces that
do not exist upstream, the appropriate behavior is dictated by the corresponding
branch of the Android common kernel.</p>
<h3 id="procfs">procfs</h3>
<table>
<tr>
<th>Path</th>
<th>Description</th>
</tr>
<tr>
<td><code>/proc/cmdline</code></td>
<td>Read-only file containing command line arguments passed to the kernel.
</td>
</tr>
<tr>
<td><code>/proc/config.gz</code></td>
<td>Read-only file containing kernel build configuration.</td>
</tr>
<tr>
<td><code>/proc/cpuinfo</code></td>
<td>Read-only file containing architecture-specific CPU details.</td>
</tr>
<tr>
<td><code>/proc/kmsg</code></td>
<td>Read-only file showing kernel messages in real time.</td>
</tr>
<tr>
<td><code>/proc/meminfo</code></td>
<td>Read-only file showing memory subsystem details.</td>
</tr>
<tr>
<td><code>/proc/modules</code></td>
<td>Read-only file containing information about loaded kernel modules.</td>
</tr>
<tr>
<td><code>/proc/mounts</code></td>
<td>Symlink to <code>/proc/self/mounts</code>, which is a read-only file
listing information about the mounted filesystems.</td>
</tr>
<tr>
<td><code>/proc/net/xt_qtaguid/ctrl</code></td>
<td>Read-write file providing information about tagged sockets.</td>
</tr>
<tr>
<td><code>/proc/self/maps</code></td>
<td>Read-only file containing the currently mapped memory regions and
permissions.</td>
</tr>
<tr>
<td><code>/proc/stat</code></td>
<td>Read-only file containing various kernel and system statistics.</td>
</tr>
<tr>
<td><code>/proc/sys/kernel/kptr_restrict</code></td>
<td>Read-write file that determines whether kernel pointers are printed in
<code>proc</code> files and other interfaces.</td>
</tr>
<tr>
<td><code>/proc/sys/kernel/randomize_va_space</code></td>
<td>Read-write file that determines the address layout randomization policy
for the system.</td>
</tr>
<tr>
<td><code>/proc/sys/vm/mmap_min_addr</code></td>
<td>Read-write file that determines the minimum address than can be
<code>mmap</code>'d.</td>
</tr>
<tr>
<td><code>/proc/sys/vm/mmap_rnd_bits</code></td>
<td>Read-write file that specifies the amount of randomness in
<code>mmap</code>'d addresses.</td>
</tr>
<tr>
<td><code>/proc/sys/vm/mmap_rnd_compat_bits</code></td>
<td>Read-write file that specifies the amount of randomness in
<code>mmap</code>'d addresses.</td>
</tr>
<tr>
<td><code>/proc/sys/vm/overcommit_memory</code></td>
<td>Read-write file that determines the kernel virtual memory accounting
mode.</td>
</tr>
<tr>
<td><code>/proc/uid_cputime/remove_uid_range</code></td>
<td>Write-only file that, when written, removes UIDs from being shown in
<code>/proc/uid_cputime/show_uid_stat</code>.</td>
</tr>
<tr>
<td><code>/proc/uid_cputime/show_uid_stat</code></td>
<td>Read-only file containing the time a UID's processes spent in user and
kernel space.</td>
</tr>
<tr>
<td><code>/proc/version</code></td>
<td>Read-only file containing a string describing the kernel version.</td>
</tr>
<tr>
<td><code>/proc/vmallocinfo</code></td>
<td>Read-only file containing <code>vmalloc</code>'d ranges.</td>
</tr>
<tr>
<td><code>/proc/zoneinfo</code></td>
<td>Read-only file containing information about memory zones.</td>
</tr>
</table>
<h3 id="dev">dev</h3>
<table>
<tr>
<th>Path</th>
<th>Description</th>
</tr>
<tr>
<td><code>/dev/ashmem</code></td>
<td>Anonymous shared memory device file.</td>
</tr>
<tr>
<td><code>/dev/binder</code></td>
<td>Binder device file.</td>
</tr>
<tr>
<td><code>/dev/hwbinder</code></td>
<td>Hardware binder device file.</td>
</tr>
<tr>
<td><code>/dev/tun</code></td>
<td>Universal TUN/TAP device file.</td>
</tr>
<tr>
<td><code>/dev/xt_qtaguid</code></td>
<td>QTAGUID netfilter device file.</td>
</tr>
</table>
<h3 id="sysfs">sysfs</h3>
<table>
<tr>
<th>Path</th>
<th>Description</th>
</tr>
<tr>
<td><code>/sys/devices/system/cpu/online</code></td>
<td>Read-only file showing ranges of CPUs that are currently online.</td>
</tr>
<tr>
<td><code>/sys/kernel/wakeup_reasons/last_resume_reason</code></td>
<td>Read-only file showing a textual description of why the system exited the
last instance of suspend.</td>
</tr>
<tr>
<td><code>/sys/devices/system/cpu/kernel_max</code></td>
<td>Read-only file showing the maximum CPU index supported by the kernel.
</td>
</tr>
</table>
<h3 id="selinuxfs">selinuxfs</h3>
<p>The framework mounts <code>selinuxfs</code> at <code>/sys/fs/selinux</code>.
</p>
<table>
<tr>
<th>Path</th>
<th>Description</th>
</tr>
<tr>
<td><code>/sys/fs/selinux/checkreqprot</code></td>
<td>Read/write file containing a binary flag that determines how selinux
protections are checked on <code>mmap</code> and <code>mprotect</code> calls.
</td>
</tr>
<tr>
<td><code>/sys/fs/selinux/null</code></td>
<td>Read/write null device for use by selinux.</td>
</tr>
<tr>
<td><code>/sys/fs/selinux/policy</code></td>
<td>Read-only file containing the selinux policy in binary form.</td>
</tr>
</table>
<aside class="note"><strong>Note:</strong> For details on SELinux in Android
8.0, see <a href="/security/selinux/images/SELinux_Treble.pdf">SELinux for
Android 8.0</a>.</aside>
</body>
</html>
|
