MarcoBuster/Magisk
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Boot to recovery if volume up key is held

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Forseeing the future that more and more A only system-as-root devices
would have similar bootloader behavior as the latest Samsung devices
(that is, no ramdisk will be loaded into memory when booting from
the boot partition), a solution/workaround has to be made when Magisk
is installed to the recovery partition, making custom recoveries
unable to co-exist with Magisk.

This commit allows magiskinit to read input device events from the
kernel to detect when a user holds volume key up to toggle whether
system-as-root mode is enabled. When system-as-root mode is disabled,
magiskinit will boot with ramdisk instead of cloning rootfs from system,
which in this case will boot to the recovery.
This commit is contained in:
topjohnwu 2019-04-01 03:01:05 -04:00
parent 08a70f033a
commit 71a91ac7a7
1 changed files with 56 additions and 8 deletions
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64
native/jni/core/init.cpp
View File

@ -1,3 +1,9 @@
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/mount.h>
#include <sys/sendfile.h>
#include <sys/sysmacros.h>
#include <linux/input.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
@ -5,11 +11,6 @@
#include <dirent.h>
#include <fcntl.h>
#include <libgen.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/mount.h>
#include <sys/sendfile.h>
#include <sys/sysmacros.h>
#include <functional>
#include <string_view>
@ -175,6 +176,49 @@ static inline void parse_cmdline(const std::function<void (std::string_view, con
}
}
#define test_bit(bit, array) (array[bit / 8] & (1 << (bit % 8)))
static bool check_key_combo() {
uint8_t bitmask[(KEY_MAX + 1) / 8];
int eventfd = -1;
for (int minor = 64; minor < 96; ++minor) {
if (mknod("/event", S_IFCHR | 0444, makedev(13, minor))) {
PLOGE("mknod");
continue;
}
eventfd = xopen("/event", O_RDWR | O_CLOEXEC);
unlink("/event");
if (eventfd < 0)
continue;
memset(bitmask, 0, sizeof(bitmask));
ioctl(eventfd, EVIOCGBIT(EV_KEY, sizeof(bitmask)), bitmask);
if (test_bit(KEY_POWER, bitmask) && test_bit(KEY_VOLUMEUP, bitmask)) {
// Check KEY_POWER because KEY_VOLUMEUP could be headphone input
break;
}
}
if (eventfd < 0)
return false;
// Return true if volume key up is hold for more than 3 seconds
int count = 0;
for (int i = 0; i < 500; ++i) {
memset(bitmask, 0, sizeof(bitmask));
ioctl(eventfd, EVIOCGKEY(sizeof(bitmask)), bitmask);
count = test_bit(KEY_VOLUMEUP, bitmask) ? count + 1 : 0;
if (count >= 300) {
close(eventfd);
return true;
}
// Check every 10ms
usleep(10000);
}
close(eventfd);
return false;
}
void MagiskInit::load_kernel_info() {
// Communicate with kernel using procfs and sysfs
mkdir("/proc", 0755);
@ -184,6 +228,7 @@ void MagiskInit::load_kernel_info() {
bool enter_recovery = false;
bool kirin = false;
bool recovery_mode = false;
parse_cmdline([&](auto key, auto value) -> void {
LOGD("cmdline: [%s]=[%s]\n", key.data(), value);
@ -205,21 +250,24 @@ void MagiskInit::load_kernel_info() {
parse_prop_file("/.backup/.magisk", [&](auto key, auto value) -> bool {
if (key == "RECOVERYMODE" && value == "true")
cmd.system_as_root = true;
recovery_mode = true;
return true;
});
if (kirin && enter_recovery) {
// Inform that we are actually booting as recovery
if (!cmd.system_as_root) {
if (!recovery_mode) {
if (FILE *f = fopen("/.backup/.magisk", "ae"); f) {
fprintf(f, "RECOVERYMODE=true\n");
fclose(f);
}
cmd.system_as_root = true;
recovery_mode = true;
}
}
if (recovery_mode)
cmd.system_as_root = !check_key_combo();
if (cmd.dt_dir[0] == '\0')
strcpy(cmd.dt_dir, DEFAULT_DT_DIR);