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Kernel+SystemServer: Defer creation of device nodes to userspace

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Don't create these device nodes in the Kernel, so we essentially enforce
userspace (SystemServer) to take control of this operation and to decide
how to create these device nodes.

This makes the DevFS to resemble linux devtmpfs, and allows us to remove
a bunch of unneeded overriding implementations of device name creation
in the Kernel.
This commit is contained in:
Liav A 2021-08-14 05:04:56 +03:00 • committed by Andreas Kling
parent fcc046047f
commit e0d712c6f7
7 changed files with 144 additions and 45 deletions
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84
Userland/Services/SystemServer/main.cpp
View file

@ -14,6 +14,7 @@
#include <LibCore/EventLoop.h>
#include <LibCore/File.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <signal.h>
#include <stdio.h>
@ -102,6 +103,61 @@ static void chown_all_matching_device_nodes(group* group, unsigned major_number)
}
}
constexpr unsigned encoded_device(unsigned major, unsigned minor)
{
return (minor & 0xff) | (major << 8) | ((minor & ~0xff) << 12);
}
static void populate_devfs()
{
mode_t old_mask = umask(0);
if (auto rc = mknod("/dev/audio", 0220 | S_IFCHR, encoded_device(42, 42)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/console", 0666 | S_IFCHR, encoded_device(5, 1)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/fb0", 0666 | S_IFBLK, encoded_device(29, 0)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/full", 0660 | S_IFCHR, encoded_device(29, 0)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/hda", 0600 | S_IFBLK, encoded_device(3, 0)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/hvc0p0", 0666 | S_IFCHR, encoded_device(229, 0)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/hwrng", 0666 | S_IFCHR, encoded_device(10, 183)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/keyboard0", 0660 | S_IFCHR, encoded_device(85, 0)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/mem", 0660 | S_IFCHR, encoded_device(1, 1)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/mouse0", 0660 | S_IFCHR, encoded_device(10, 0)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/null", 0666 | S_IFCHR, encoded_device(1, 3)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/ptmx", 0666 | S_IFCHR, encoded_device(5, 2)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/random", 0666 | S_IFCHR, encoded_device(1, 8)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/tty0", 0620 | S_IFCHR, encoded_device(4, 0)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/tty1", 0620 | S_IFCHR, encoded_device(4, 1)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/tty2", 0620 | S_IFCHR, encoded_device(4, 2)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/tty3", 0620 | S_IFCHR, encoded_device(4, 3)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/ttyS0", 0620 | S_IFCHR, encoded_device(4, 64)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/ttyS1", 0620 | S_IFCHR, encoded_device(4, 65)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/ttyS2", 0620 | S_IFCHR, encoded_device(4, 66)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/ttyS3", 0666 | S_IFCHR, encoded_device(4, 67)); rc < 0)
VERIFY_NOT_REACHED();
if (auto rc = mknod("/dev/zero", 0666 | S_IFCHR, encoded_device(1, 5)); rc < 0)
VERIFY_NOT_REACHED();
umask(old_mask);
}
static void prepare_devfs()
{
// FIXME: Find a better way to all of this stuff, without hardcoding all of this!
@ -111,6 +167,8 @@ static void prepare_devfs()
VERIFY_NOT_REACHED();
}
populate_devfs();
rc = mount(-1, "/sys", "sys", 0);
if (rc != 0) {
VERIFY_NOT_REACHED();
@ -162,6 +220,32 @@ static void prepare_devfs()
VERIFY_NOT_REACHED();
}
// Note: We open the /dev/null device and set file descriptors 0, 1, 2 to it
// because otherwise these file descriptors won't have a custody, making
// the ProcFS file descriptor links (at /proc/PID/fd/{0,1,2}) to have an
// absolute path of "device:1,3" instead of something like "/dev/null".
// This affects also every other process that inherits the file descriptors
// from SystemServer, so it is important for other things (also for ProcFS
// tests that are running in CI mode).
int stdin_new_fd = open("/dev/null", O_NONBLOCK);
if (stdin_new_fd < 0) {
VERIFY_NOT_REACHED();
}
rc = dup2(stdin_new_fd, 0);
if (rc < 0) {
VERIFY_NOT_REACHED();
}
rc = dup2(stdin_new_fd, 1);
if (rc < 0) {
VERIFY_NOT_REACHED();
}
rc = dup2(stdin_new_fd, 2);
if (rc < 0) {
VERIFY_NOT_REACHED();
}
endgrent();
}