高通安卓:de参数控制系统流程原理
⾼通安卓：de参数控制系统流程原理
⾼通安卓：de参数控制系统流程原理
背景
在做出⼚功能测试的时候，看到之前做开发时进⼊ffbm模式以后的cmdline中对应的字段为de=ffbm-01；⽽现在项⽬中的cmdline 对应的是de=ffbm-02。⽽且界⾯上也不太⼀样，⼀种是C/C++实现的；⼀种是直接可以在界⾯上点击的QMMI。
现在我也到了答案：
FFBM对应ffbm-00或ffbm-00
// system/core/fs_mgr/fs_mgr.cpp
int fs_mgr_mount_all(struct fstab *fstab, int mount_mode)
{
int i = 0;
int encryptable = FS_MGR_MNTALL_DEV_NOT_ENCRYPTABLE;
int error_count = 0;
int mret = -1;
int mount_errno = 0;
int attempted_idx = -1;
FsManagerAvbUniquePtr avb_handle(nullptr);
char propbuf[PROPERTY_VALUE_MAX];
bool is_ffbm = false;
if (!fstab) {
return FS_MGR_MNTALL_FAIL;
}
/
**get boot mode*/
property_get("ro.bootmode", propbuf, "");
if ((strncmp(propbuf, "ffbm-00", 7) == 0) || (strncmp(propbuf, "ffbm-01", 7) == 0))
is_ffbm = true;
// ..
}
QMMI对应ffbm-02
// vendor/qcom/proprietary/commonsys/fastmmi/qmmi/src/com/qualcomm/qti/qmmi/framework/QmmiReceiver.java
public class QmmiReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
String bootmode = SystemProperties("ro.bootmode", "00");
LogUtils.logi("bootmode:" + bootmode);
if (Action().equals(Intent.ACTION_BOOT_COMPLETED) && bootmode.equals("ffbm-02")) {
LogUtils.logi("receive boot complete");
startMainActivity(context);
} else if (Action().equals("android.provider.Telephony.SECRET_CODE")) {
LogUtils.logi("receive SECRET_CODE ");
startMainActivity(context);
}
}
// ...
}
流程解析
BootLoader针对ffbm的处理
以uefi为例。
判断进⼊FFBM模式
路径：bootable/bootloader/edk2/QcomModulePkg/Application/LinuxLoader/LinuxLoader.c
EFI_STATUS EFIAPI  __attribute__ ( (no_sanitize ("safe-stack")))
LinuxLoaderEntry (IN EFI_HANDLE ImageHandle, IN EFI_SYSTEM_TABLE *SystemTable)
{
// ...
Status = GetKeyPress (&KeyPressed);
DEBUG ((EFI_D_ERROR, "reading key status: %r \n", Status));
DEBUG ((EFI_D_ERROR, "reading key status: %d \n", KeyPressed));
if (Status == EFI_SUCCESS) {
if (KeyPressed == SCAN_DOWN ||KeyPressed == SCAN_DELETE)
BootIntoFastboot = TRUE;
if (KeyPressed == SCAN_UP)
BootIntoRecovery = TRUE;
if (KeyPressed == SCAN_ESC)
RebootDevice (EMERGENCY_DLOAD);
if (KeyPressed == SCAN_HOME)  //POWER+VOL UP will generate SCAN_HOME, detect this key, it will enter ffbm mode
{
DEBUG ((EFI_D_ERROR, "go to ffbm mode\n"));
SetFFBMCommand(); // 设置 de=ffbm-xxx
}
} else if (Status == EFI_DEVICE_ERROR) {
DEBUG ((EFI_D_ERROR, "Error reading key status: %r\n", Status));
goto stack_guard_update_default;
}
// ...
}
在cmdline中传递启动模式
BootLoader把对应的启动模式通过 command line的⽅式传送给内核。
在uefi中解释这个过程需要⼀定的UEFI基础，因此不详细展开，但是实际上基于的就是检查SetFFBMCommand的调⽤。其中涉及到了针对分区的写操作。
// bootable/bootloader/edk2/QcomModulePkg/Library/BootLib/Recovery.c
EFI_STATUS SetFFBMCommand(VOID)
{
EFI_STATUS Status = EFI_SUCCESS;
CHAR8 FfbmPageBuffer[FFBM_MODE_BUF_SIZE] = "";
EFI_GUID Ptype = gEfiMiscPartitionGuid; // 杂项设备分区
MemCardType CardType = UNKNOWN;
CardType = CheckRootDeviceType ();
if (CardType == NAND) {
Status = GetNandMiscPartiGuid (&Ptype);
if (Status != EFI_SUCCESS) {
return Status;
}
}
AsciiSPrint (FfbmPageBuffer, sizeof (FfbmPageBuffer), "ffbm-02");
WriteToPartition (&Ptype, FfbmPageBuffer, sizeof (FfbmPageBuffer));
return Status;
}
内核
路径：system/core/init/init.cpp
内核解析cmdline，并设置对应的系统属性。
int main(int argc, char** argv) {
// ...
// If arguments are passed both on the command line and in DT,
// properties set in DT always have priority over the command-line ones.
process_kernel_dt();
process_kernel_cmdline(); // 解析命令⾏
// Propagate the kernel variables to internal variables
// used by init as well as the current required properties.
export_kernel_boot_props();
// ...
// Don't mount filesystems or start core system services in charger mode.
std::string bootmode = GetProperty("ro.bootmode", "");
if (bootmode == "charger") {
am.QueueEventTrigger("charger");
} else {
am.QueueEventTrigger("late-init");
}
// ...
}
解析command line
路径：
system/core/init/util.cpp
system/core/init/init.cpp
// system/core/init/util.cpp
void import_kernel_cmdline(bool in_qemu,
const std::function<void(const std::string&, const std::string&, bool)>& fn) {    std::string cmdline;
android::base::ReadFileToString("/proc/cmdline", &cmdline);
for (const auto& entry : android::base::Split(android::base::Trim(cmdline), " ")) {
std::vector<std::string> pieces = android::base::Split(entry, "=");
if (pieces.size() == 2) {
fn(pieces[0], pieces[1], in_qemu);
}
}
}
// system/core/init/init.cpp
static void import_kernel_nv(const std::string& key, const std::string& value, bool for_emulator) {    if (pty()) return;
if (for_emulator) {
// In the emulator, export any kernel option with the "ro.kernel." prefix.
property_set("ro.kernel." + key, value);
return;
}
// 实际上的cmdline ： de=ffbm-02
if (key == "qemu") {
strlcpy(qemu, value.c_str(), sizeof(qemu));
} else if (android::base::StartsWith(key, "androidboot.")) {
// 写配置，相当于：de = ffbm-02
property_set("ro.boot." + key.substr(12), value);
}
}
// system/core/init/init.cpp
static void process_kernel_cmdline() {
// The first pass does the common stuff, and finds if we are in qemu.
// The second pass is only necessary for qemu to export all kernel params
// as properties.
import_kernel_cmdline(false, import_kernel_nv);
if (qemu[0]) import_kernel_cmdline(true, import_kernel_nv);
}
设置对应的系统属性
将解析cmdline写的配置导出（实际上就是换个名字）。
static void export_kernel_boot_props() {
struct {
const char *src_prop;
const char *dst_prop;
const char *default_value;
} prop_map[] = {
{ "ro.boot.serialno",  "ro.serialno",  "", },
{ "de",      "ro.bootmode",  "unknown", },
{ "ro.boot.baseband",  "ro.baseband",  "unknown", },
{ "ro.boot.bootloader", "ro.bootloader", "unknown", },
{ "ro.boot.hardware",  "ro.hardware",  "unknown", },
{ "vision",  "ro.revision",  "0", },
};
for (size_t i = 0; i < arraysize(prop_map); i++) {
std::string value = GetProperty(prop_map[i].src_prop, "");
property_set(prop_map[i].dst_prop, (!pty()) ? value : prop_map[i].default_value);    }
}
最终：
[de]: [ffbm-00]
[ro.bootmode]: [ffbm-00]
此后，关于启动模式的处理都以ro.bootmode为准。
安卓系统启动相关进程
当ro.bootmode设置了以后，对应的rc解析就会根据这些内容进⾏处理。
<
还记得吗，在init.cpp中执⾏了am.QueueEventTrigger("late-init")；导致下⾯的rc被执⾏。路径：system/core/
on late-init
trigger early-fs
# Mount fstab in init.{$device}.rc by mount_all command. Optional parameter
# '--early' can be specified to skip entries with 'latemount'.
# /system and /vendor must be mounted by the end of the fs stage,
# while /data is optional.
trigger factory-fs
trigger fs
trigger post-fs
# Mount fstab in init.{$device}.rc by mount_all with '--late' parameter
# to only mount entries with 'latemount'. This is needed if '--early' is
# specified in the previous mount_all command on the fs stage.
# With /system mounted and properties form /system + /factory available,
# some services can be started.
trigger late-fs
# Now we can mount /data. File encryption requires keymaster to decrypt
# /data, which in turn can only be loaded when system properties are present.
trigger post-fs-data
# Now we can start zygote for devices with file based encryption
trigger zygote-start
# Load persist properties and override properties (if enabled) from /data.
trigger load_persist_props_action
# Remove a file to wake up anything waiting for firmware.
trigger firmware_mounts_complete
trigger early-boot
trigger boot
trigger mmi # 触发了 mmi 这个触发器
init.
路径：device/qcom/common/rootdir/etc/init.uefi boot
on property:vendor.sys.boot_mode=ffbm
write ${i.misc_dev_path} "ffbm-01"
on property:vendor.sys.boot_mode=qmmi
write ${i.misc_dev_path} "ffbm-02"
on property:vendor.sys.boot_mode=normal
write ${i.misc_dev_path} "normal"
# Creating a scratch storage on /data for factory testing.
on factory-fs && property:ro.bootmode=ffbm-00
mount tmpfs tmpfs /data
on factory-fs && property:ro.bootmode=ffbm-01
mount tmpfs tmpfs /data
# aligned the usb port with system standard, otherwise if only diag be added
# Then in QMMI mode, the whole Andoid be booted, but due to the ro.bootmode is
# not normal/unknow, then when it apply the default funcs, it will turn to MTP
# which cause the diag/Wwan/modem port all be lost in qmmi mode. Details:
# UsbDeviceManager.java---->getDefaultFunctions and trySetEnabledFunctions
on property:persist.fig=*
setprop persist.sys.usb.ffbm-02.func ${persist.fig}
on mmi && property:ro.bootmode=ffbm-00
# ========================================================
#              This is FFBM only settings.
# ========================================================
#mkdir for factory data files.
mkdir /mnt/vendor/persist/FTM_AP 0750 system system
start fastmmi
# start qcom-post-boot to set the misc partition path property value
start qcom-post-boot
start mmi_diag
on mmi && property:ro.bootmode=ffbm-01
# ========================================================
#              This is FFBM only settings.
# ========================================================    #mkdir for factory data files.
mkdir /mnt/vendor/persist/FTM_AP 0750 system system
start fastmmi
## start qcom-post-boot to set the misc partition path property value
start qcom-post-boot
start mmi_diag
on mmi && property:ro.bootmode=ffbm-02 #▲注意，启动了这个
#mkdir for factory data files.
mkdir /mnt/vendor/persist/FTM_AP 0750 system system
start fastmmi
## start qcom-post-boot to set the misc partition path property value
start qcom-post-boot
start mmi_diag
on property:persist.fig=* && property:ro.bootmode=ffbm-00
setprop fig ${persist.fig}
on property:persist.fig=* && property:ro.bootmode=ffbm-01
setprop fig ${persist.fig}
on property:persist.fig=* && property:ro.bootmode=ffbm-02
setprop fig ${persist.fig}
#### 做最⼩系统的启动
on ffbm
trigger early-fs
trigger factory-fs
trigger fs
trigger post-fs
# Mount fstab in init.{$device}.rc by mount_all with '--late' parameter
# to only mount entries with 'latemount'. This is needed if '--early' is
# specified in the previous mount_all command on the fs stage.
# With /system mounted and properties form /system + /factory available,
# some services can be started.
trigger late-fs
# Now we can mount /data. File encryption requires keymaster to decrypt
# /data, which in turn can only be loaded when system properties are present.    trigger post-fs-data
# Now we can start zygote for devices with file based encryption
trigger zygote-start
# Load persist properties and override properties (if enabled) from /data.
trigger load_persist_props_action
# Remove a file to wake up anything waiting for firmware.
trigger firmware_mounts_complete
trigger early-boot
trigger boot
trigger mmi

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