mediatek: Introduce create_pl_dev for updating preloader

* Most OEMs who use MediaTek tend to ship preloader images without
  a header, therefore to allow preloader updates, it's necessary to
  create DM devices that allow writing to the physical preloader partition
  without the header.

Change-Id: I6c3168ecabca4d4e56893d2a1bfea6a256577bd0
Signed-off-by: bengris32 <bengris32@protonmail.ch>

create_pl_dev/Android.bp

@@ -0,0 +1,18 @@
+//
+// SPDX-FileCopyrightText: 2024 The LineageOS Project
+// SPDX-License-Identifier: Apache-2.0
+//
+
+cc_binary {
+    name: "create_pl_dev",
+    srcs: ["create_pl_dev.cpp"],
+    init_rc: ["create_pl_dev.rc"],
+    recovery_available: true,
+    static_libs: [
+        "libfs_mgr"
+    ],
+    shared_libs: [
+        "libbase",
+        "liblog",
+    ],
+}

create_pl_dev/create_pl_dev.cpp

@@ -0,0 +1,120 @@
+/*
+ * SPDX-FileCopyrightText: 2024 The LineageOS Project
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define LOG_TAG "create_pl_dev"
+
+#include <android-base/unique_fd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <libdm/dm.h>
+#include <log/log.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#define BLOCK_SIZE 512
+
+#define EMMC_HSZ 0x800
+#define UFS_HSZ 0x1000
+
+#define COMBO_HEADER_SIZE 4
+#define UFS_HEADER_SIZE 3
+
+#define UFS_HEADER "UFS"
+#define EMMC_HEADER "EMMC"
+#define COMBO_HEADER "COMB"
+
+using namespace android::dm;
+
+struct pl_device {
+    const char* dm_name;
+    const char* dev;
+};
+
+static struct pl_device pl_devices[] = {
+        {"preloader_raw_a", "/dev/block/sda"},
+        {"preloader_raw_b", "/dev/block/sdb"},
+        {"preloader_raw_a", "/dev/block/mmcblk0boot0"},
+        {"preloader_raw_b", "/dev/block/mmcblk0boot1"},
+};
+
+static void create_dm_device(const char* name, const char* dev, int start, int count) {
+    DeviceMapper& dm = DeviceMapper::Instance();
+    DmTable table;
+    std::unique_ptr<DmTarget> target;
+    std::string path;
+
+    target = std::make_unique<DmTargetLinear>(0, count, dev, start);
+    if (!table.AddTarget(std::move(target))) {
+        ALOGE("Failed to add target for %s.", name);
+        return;
+    }
+
+    if (!dm.CreateDevice(name, table, &path, std::chrono::milliseconds(500))) {
+        ALOGE("Failed to create device %s.", name);
+        return;
+    }
+
+    ALOGI("Created DM device %s at %s.", name, path.c_str());
+}
+
+int main() {
+    int fd, size, count, start;
+    char header[COMBO_HEADER_SIZE];
+
+    for (int i = 0; i < sizeof(pl_devices) / sizeof(pl_device); i++) {
+        pl_device* device = &pl_devices[i];
+
+        if (access(device->dev, F_OK) == -1) {
+            ALOGE("Device %s not found.", device->dev);
+            continue;
+        }
+
+        fd = open(device->dev, O_RDONLY);
+        if (fd == -1) {
+            ALOGE("Failed to open %s: %s.", device->dev, strerror(errno));
+            continue;
+        }
+
+        size = lseek(fd, 0, SEEK_END);
+        if (size == -1) {
+            ALOGE("Failed to seek %s: %s.", device->dev, strerror(errno));
+            close(fd);
+            continue;
+        }
+
+        count = size / BLOCK_SIZE;
+
+        if (lseek(fd, 0, SEEK_SET) == -1) {
+            ALOGE("Failed to seek %s: %s.", device->dev, strerror(errno));
+            close(fd);
+            continue;
+        }
+
+        if (read(fd, header, COMBO_HEADER_SIZE) != COMBO_HEADER_SIZE) {
+            ALOGE("Failed to read %s: %s.", device->dev, strerror(errno));
+            close(fd);
+            continue;
+        }
+
+        close(fd);
+
+        if (strncmp(header, UFS_HEADER, UFS_HEADER_SIZE) == 0 ||
+            strncmp(header, COMBO_HEADER, COMBO_HEADER_SIZE) == 0) {
+            start = UFS_HSZ / BLOCK_SIZE;
+        } else if (strncmp(header, EMMC_HEADER, COMBO_HEADER_SIZE) == 0) {
+            start = EMMC_HSZ / BLOCK_SIZE;
+        } else {
+            ALOGE("Unknown header %s for %s.", header, device->dev);
+            continue;
+        }
+
+        count -= start;
+
+        create_dm_device(device->dm_name, device->dev, start, count);
+    }
+
+    return 0;
+}

create_pl_dev/create_pl_dev.rc

@@ -0,0 +1,27 @@
+on post-fs
+    start create_pl_dev
+
+    wait /dev/block/mapper/preloader_raw_a
+    wait /dev/block/mapper/preloader_raw_b
+
+    symlink /dev/block/mapper/preloader_raw_a /dev/block/by-name/preloader_raw_a
+    symlink /dev/block/mapper/preloader_raw_b /dev/block/by-name/preloader_raw_b
+
+    symlink /dev/block/mapper/preloader_raw_a /dev/block/platform/bootdevice/by-name/preloader_raw_a
+    symlink /dev/block/mapper/preloader_raw_b /dev/block/platform/bootdevice/by-name/preloader_raw_b
+
+    symlink /dev/block/mapper/preloader_raw_a /dev/block/platform/11270000.ufshci/by-name/preloader_raw_a
+    symlink /dev/block/mapper/preloader_raw_b /dev/block/platform/11270000.ufshci/by-name/preloader_raw_b
+
+    symlink /dev/block/mapper/preloader_raw_a /dev/block/platform/11230000.mmc/by-name/preloader_raw_a
+    symlink /dev/block/mapper/preloader_raw_b /dev/block/platform/11230000.mmc/by-name/preloader_raw_b
+
+    symlink /dev/block/mapper/preloader_raw_a /dev/block/platform/11230000.msdc/by-name/preloader_raw_a
+    symlink /dev/block/mapper/preloader_raw_b /dev/block/platform/11230000.msdc/by-name/preloader_raw_b
+
+service create_pl_dev /system/bin/create_pl_dev
+    user root
+    group root
+    seclabel u:r:update_engine:s0
+    oneshot
+    disabled