Android10 uml調試之一

1. init編譯

init第一階段的會被編譯到ramdisk.img中，init第二階段會被編譯進system.img中。
ramdisk會掛載成rootfs,system.img會被掛載成system分區。
kernel會首先加載/init。

把init編譯進去

diff --git a/uml.mk b/uml.mk
index 03db5e9..9b7558e 100644
--- a/uml.mk
+++ b/uml.mk
@@ -49,6 +49,8 @@ PRODUCT_PACKAGES += \
     healthd \
     hwservicemanager \
     init \
+    init_system \
+    init_vendor \
     init.environ.rc \
     init.rc \
     libEGL \

2. 沒有掛載system系統

報錯找不到/system/bin/init,也就是system分區沒有掛載成功.

diff --git a/uml.mk b/uml.mk
index 03db5e9..9b7558e 100644
--- a/uml.mk
+++ b/uml.mk
@@ -49,6 +49,8 @@ PRODUCT_PACKAGES += \
     healthd \
     hwservicemanager \
     init \
+    init_system \
+    init_vendor \
     init.environ.rc \
     init.rc \
     libEGL \
@@ -123,6 +125,7 @@ PRODUCT_SYSTEM_DEFAULT_PROPERTIES += \
     debug.atrace.tags.enableflags=0
 
 PRODUCT_COPY_FILES += \
+    device/generic/uml/fstab.uml.initrd:$(TARGET_COPY_OUT_RAMDISK)/fstab.uml \
     system/core/rootdir/init.usb.rc:root/init.usb.rc \
     system/core/rootdir/init.usb.configfs.rc:root/init.usb.configfs.rc \
     system/core/rootdir/ueventd.rc:root/ueventd.rc \

新添加的文件fstab.uml.initrd內容如下:

tom@tom-linuxer:~/work/aosp/device/generic/uml$ cat fstab.uml.initrd 
# Android fstab file for ramdisk tom -3
#<dev>  <mnt_point> <type>  <mnt_flags options> <fs_mgr_flags>
#vendor   /vendor     ext4    ro,barrier=1     wait,logical,first_stage_mount
/dev/block/ubda   /system     ext4    ro,barrier=1     wait,logical,avb=vbmeta,first_stage_mount

3. 還是報錯

Initializing XFRM netlink socket
NET: Registered protocol family 10
Segment Routing with IPv6
mip6: Mobile IPv6
ip6_tables: (C) 2000-2006 Netfilter Core Team
sit: IPv6, IPv4 and MPLS over IPv4 tunneling driver
NET: Registered protocol family 17
NET: Registered protocol family 15
Initialized stdio console driver
Console initialized on /dev/tty0
console [tty0] enabled
Initializing software serial port version 1
console [mc-1] enabled
registered taskstats version 1
This architecture does not have kernel memory protection.
init: init first stage started!
init: [libfs_mgr]ReadFstabFromDt(): failed to read fstab from dt
init: Using Android DT directory /proc/device-tree/firmware/android/
init: bool android::init::FirstStageMount::InitRequiredDevices(): partition(s) not found in /sys, waiting for their uevent(s): super, vbmeta

感覺要從kernel中找到ueventd消息，現在邏輯不清楚。

在文件core/init/uevent_listener.cpp中。

 98 bool UeventListener::ReadUevent(Uevent* uevent) const {                         
 99     char msg[UEVENT_MSG_LEN + 2];                                               
100     int n = uevent_kernel_multicast_recv(device_fd_, msg, UEVENT_MSG_LEN);      
101     if (n <= 0) {                                                               
102         if (errno != EAGAIN && errno != EWOULDBLOCK) {                          
103             LOG(ERROR) << "Error reading from Uevent Fd";                       
104         }                                                                       
105         return false;                                                           
106     }                                                                           
107     if (n >= UEVENT_MSG_LEN) {                                                  
108         LOG(ERROR) << "Uevent overflowed buffer, discarding";                   
109         // Return true here even if we discard as we may have more uevents pending and we
110         // want to keep processing them.                                        
111         return true;                                                            
112     }                                                                           
113                                                                                 
114     msg[n] = '\0';                                                              
115     msg[n + 1] = '\0';                                                          
116                                                                                 
117     ParseEvent(msg, uevent);                                                    
118                                                                                 
119     return true;                                                                
120 }                                                                               
121    

4. 原因分析

函數

調試log

[    1.399694] init: Using Android DT directory /proc/device-tree/firmware/android/
[    1.406997] init: tom action=add path=/devices/pci0000:00/0000:00:03.0/virtio0/block/vda/vda2 subsystem=block
[    1.407819] init: tom firmware= p_name=super
[    1.408182] init: tom device_name=vda2 modifies=
[    1.408567] init: tom partition_num=2 major=253 minor=2
[    1.409392] init: tom action=add path=/devices/pci0000:00/0000:00:03.0/virtio0/block/vda/vda1 subsystem=block
[    1.410304] init: tom firmware= p_name=vbmeta
[    1.410827] init: tom device_name=vda1 modifies=
[    1.411399] init: tom partition_num=1 major=253 minor=1