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Commit c01022a6 authored by Yu Ning's avatar Yu Ning
Browse files

Allow the use of a custom Android DT directory 

On platforms that use ACPI instead of Device Tree (DT), such as
Ranchu x86/x86_64, /proc/device-tree/firmware/android/ does not
exist. As a result, Android O is unable to mount /system, etc.
at the first stage of init:

 init: First stage mount skipped (missing/incompatible fstab in
 device tree)

Those platforms may create another directory that mimics the layout
of the standard DT directory in procfs, and store early mount
configuration there. E.g., Ranchu x86/x86_64 creates one in sysfs
using information encoded in the ACPI tables:

 https://android-review.googlesource.com/442472
 https://android-review.googlesource.com/443432
 https://android-review.googlesource.com/442393
 https://android-review.googlesource.com/442395



Therefore, instead of hardcoding the Android DT path, load it from
the kernel command line using a new Android-specific property key
("androidboot.android_dt_dir"). If no such property exists, fall
back to the standard procfs path (so no change is needed for DT-
aware platforms).

Note that init/ and fs_mgr/ each have their own copy of the Android
DT path, because they do not share any global state. A future CL
should remove the duplication by refactoring.

With this CL as well as the above ones, the said warning is gone,
but early mount fails. That is a separate bug, though, and will be
addressed by another CL.

Test: Boot patched sdk_phone_x86-userdebug system image with patched
      Goldfish 3.18 x86 kernel in patched Android Emulator, verify
      the "init: First stage mount skipped" warning no longer shows
      in dmesg.

Change-Id: Ib6df577319503ec1ca778de2b5458cc72ce07415
Signed-off-by: default avatarYu Ning <yu.ning@intel.com>
parent 603cae8b

fs_mgr/fs_mgr_boot_config.cpp

+24 −12
Original line number Diff line number Diff line
@@ -23,19 +23,11 @@ 


#include "fs_mgr_priv.h"



// Tries to get the boot config value in properties, kernel cmdline and

// device tree (in that order).  returns 'true' if successfully found, 'false'

// otherwise

bool fs_mgr_get_boot_config(const std::string& key, std::string* out_val) {

// Tries to get the given boot config value from kernel cmdline.

// Returns true if successfully found, false otherwise.

bool fs_mgr_get_boot_config_from_kernel_cmdline(const std::string& key, std::string* out_val) {

    FS_MGR_CHECK(out_val != nullptr);



    // first check if we have "ro.boot" property already

    *out_val = android::base::GetProperty("ro.boot." + key, "");

    if (!out_val->empty()) {

        return true;

    }



    // fallback to kernel cmdline, properties may not be ready yet

    std::string cmdline;

    std::string cmdline_key("androidboot." + key);

    if (android::base::ReadFileToString("/proc/cmdline", &cmdline)) {
@@ -50,9 +42,29 @@ bool fs_mgr_get_boot_config(const std::string& key, std::string* out_val) { 
        }

    }



    return false;

}



// Tries to get the boot config value in properties, kernel cmdline and

// device tree (in that order).  returns 'true' if successfully found, 'false'

// otherwise

bool fs_mgr_get_boot_config(const std::string& key, std::string* out_val) {

    FS_MGR_CHECK(out_val != nullptr);



    // first check if we have "ro.boot" property already

    *out_val = android::base::GetProperty("ro.boot." + key, "");

    if (!out_val->empty()) {

        return true;

    }



    // fallback to kernel cmdline, properties may not be ready yet

    if (fs_mgr_get_boot_config_from_kernel_cmdline(key, out_val)) {

        return true;

    }



    // lastly, check the device tree

    if (is_dt_compatible()) {

        std::string file_name = kAndroidDtDir + "/" + key;

        std::string file_name = get_android_dt_dir() + "/" + key;

        if (android::base::ReadFileToString(file_name, out_val)) {

            if (!out_val->empty()) {

                out_val->pop_back();  // Trims the trailing '\0' out.

fs_mgr/fs_mgr_fstab.cpp

+22 −3
Original line number Diff line number Diff line
@@ -29,6 +29,8 @@ 


#include "fs_mgr_priv.h"



const std::string kDefaultAndroidDtDir("/proc/device-tree/firmware/android");



struct fs_mgr_flag_values {

    char *key_loc;

    char *verity_loc;
@@ -313,9 +315,26 @@ static int parse_flags(char *flags, struct flag_list *fl, 
    return f;

}



static std::string init_android_dt_dir() {

    std::string android_dt_dir;

    // The platform may specify a custom Android DT path in kernel cmdline

    if (!fs_mgr_get_boot_config_from_kernel_cmdline("android_dt_dir", &android_dt_dir)) {

        // Fall back to the standard procfs-based path

        android_dt_dir = kDefaultAndroidDtDir;

    }

    return android_dt_dir;

}



// FIXME: The same logic is duplicated in system/core/init/

const std::string& get_android_dt_dir() {

    // Set once and saves time for subsequent calls to this function

    static const std::string kAndroidDtDir = init_android_dt_dir();

    return kAndroidDtDir;

}



static bool is_dt_fstab_compatible() {

    std::string dt_value;

    std::string file_name = kAndroidDtDir + "/fstab/compatible";

    std::string file_name = get_android_dt_dir() + "/fstab/compatible";

    if (read_dt_file(file_name, &dt_value)) {

        if (dt_value == "android,fstab") {

            return true;
@@ -331,7 +350,7 @@ static std::string read_fstab_from_dt() { 
        return fstab;

    }



    std::string fstabdir_name = kAndroidDtDir + "/fstab";

    std::string fstabdir_name = get_android_dt_dir() + "/fstab";

    std::unique_ptr<DIR, int (*)(DIR*)> fstabdir(opendir(fstabdir_name.c_str()), closedir);

    if (!fstabdir) return fstab;
@@ -394,7 +413,7 @@ static std::string read_fstab_from_dt() { 
}



bool is_dt_compatible() {

    std::string file_name = kAndroidDtDir + "/compatible";

    std::string file_name = get_android_dt_dir() + "/compatible";

    std::string dt_value;

    if (read_dt_file(file_name, &dt_value)) {

        if (dt_value == "android,firmware") {

fs_mgr/fs_mgr_priv.h

+1 −0
Original line number Diff line number Diff line
@@ -119,6 +119,7 @@ bool fs_mgr_wait_for_file(const std::string& filename, 
                          const std::chrono::milliseconds relative_timeout);

bool fs_mgr_update_for_slotselect(struct fstab *fstab);

bool fs_mgr_is_device_unlocked();

const std::string& get_android_dt_dir();

bool is_dt_compatible();

bool is_device_secure();

int load_verity_state(struct fstab_rec* fstab, int* mode);

fs_mgr/fs_mgr_priv_boot_config.h

+1 −2
Original line number Diff line number Diff line
@@ -20,8 +20,7 @@ 
#include <sys/cdefs.h>

#include <string>



const std::string kAndroidDtDir("/proc/device-tree/firmware/android");



bool fs_mgr_get_boot_config_from_kernel_cmdline(const std::string& key, std::string* out_val);

bool fs_mgr_get_boot_config(const std::string& key, std::string* out_val);



#endif /* __CORE_FS_MGR_PRIV_BOOTCONFIG_H */

init/init.cpp

+2 −2
Original line number Diff line number Diff line
@@ -513,7 +513,7 @@ static void process_kernel_dt() { 
        return;

    }



    std::unique_ptr<DIR, int (*)(DIR*)> dir(opendir(kAndroidDtDir.c_str()), closedir);

    std::unique_ptr<DIR, int (*)(DIR*)> dir(opendir(get_android_dt_dir().c_str()), closedir);

    if (!dir) return;



    std::string dt_file;
@@ -523,7 +523,7 @@ static void process_kernel_dt() { 
            continue;

        }



        std::string file_name = kAndroidDtDir + dp->d_name;

        std::string file_name = get_android_dt_dir() + dp->d_name;



        android::base::ReadFileToString(file_name, &dt_file);

        std::replace(dt_file.begin(), dt_file.end(), ',', '.');