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Commit 922cfefb authored by David Anderson's avatar David Anderson
Browse files

liblp: Add a helper to differentiate empty from non-empty images. 

Also, finally explain the difference between these somewhere.

Bug: 140204341
Test: lpdump
Change-Id: I128780b01a28e893afac65f3aa4f4a8d36032d63
parent 50e408db

fs_mgr/liblp/images.cpp

+34 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include "images.h"



#include <limits.h>

#include <sys/stat.h>



#include <android-base/file.h>
@@ -27,12 +28,45 @@ 
namespace android {

namespace fs_mgr {



using android::base::borrowed_fd;

using android::base::unique_fd;



#if defined(_WIN32)

static const int O_NOFOLLOW = 0;

#endif



static bool IsEmptySuperImage(borrowed_fd fd) {

    struct stat s;

    if (fstat(fd.get(), &s) < 0) {

        PERROR << __PRETTY_FUNCTION__ << " fstat failed";

        return false;

    }

    if (s.st_size < LP_METADATA_GEOMETRY_SIZE) {

        return false;

    }



    // Rewind back to the start, read the geometry struct.

    LpMetadataGeometry geometry = {};

    if (SeekFile64(fd.get(), 0, SEEK_SET) < 0) {

        PERROR << __PRETTY_FUNCTION__ << " lseek failed";

        return false;

    }

    if (!android::base::ReadFully(fd, &geometry, sizeof(geometry))) {

        PERROR << __PRETTY_FUNCTION__ << " read failed";

        return false;

    }

    return geometry.magic == LP_METADATA_GEOMETRY_MAGIC;

}



bool IsEmptySuperImage(const std::string& file) {

    unique_fd fd = GetControlFileOrOpen(file, O_RDONLY | O_CLOEXEC);

    if (fd < 0) {

        PERROR << __PRETTY_FUNCTION__ << " open failed";

        return false;

    }

    return IsEmptySuperImage(fd);

}



std::unique_ptr<LpMetadata> ReadFromImageFile(int fd) {

    std::unique_ptr<uint8_t[]> buffer = std::make_unique<uint8_t[]>(LP_METADATA_GEOMETRY_SIZE);

    if (SeekFile64(fd, 0, SEEK_SET) < 0) {

fs_mgr/liblp/include/liblp/liblp.h

+8 −1
Original line number Diff line number Diff line
@@ -70,8 +70,15 @@ bool UpdatePartitionTable(const std::string& super_partition, const LpMetadata& 
                          uint32_t slot_number);

std::unique_ptr<LpMetadata> ReadMetadata(const std::string& super_partition, uint32_t slot_number);



// Returns whether an image is an "empty" image or not. An empty image contains

// only metadata. Unlike a flashed block device, there are no reserved bytes or

// backup sections, and only one slot is stored (even if multiple slots are

// supported). It is a format specifically for storing only metadata.

bool IsEmptySuperImage(const std::string& file);



// Read/Write logical partition metadata to an image file, for diagnostics or

// flashing.

// flashing. If no partition images are specified, the file will be in the

// empty format.

bool WriteToImageFile(const std::string& file, const LpMetadata& metadata, uint32_t block_size,

                      const std::map<std::string, std::string>& images, bool sparsify);

bool WriteToImageFile(const std::string& file, const LpMetadata& metadata);

fs_mgr/liblp/utility.cpp

+3 −3
Original line number Diff line number Diff line
@@ -205,9 +205,9 @@ bool SetBlockReadonly(int fd, bool readonly) { 
#endif

}



base::unique_fd GetControlFileOrOpen(const char* path, int flags) {

base::unique_fd GetControlFileOrOpen(std::string_view path, int flags) {

#if defined(__ANDROID__)

    int fd = android_get_control_file(path);

    int fd = android_get_control_file(path.data());

    if (fd >= 0) {

        int newfd = TEMP_FAILURE_RETRY(dup(fd));

        if (newfd >= 0) {
@@ -216,7 +216,7 @@ base::unique_fd GetControlFileOrOpen(const char* path, int flags) { 
        PERROR << "Cannot dup fd for already controlled file: " << path << ", reopening...";

    }

#endif

    return base::unique_fd(open(path, flags));

    return base::unique_fd(open(path.data(), flags));

}



bool UpdateMetadataForInPlaceSnapshot(LpMetadata* metadata, uint32_t source_slot_number,

fs_mgr/liblp/utility.h

+4 −1
Original line number Diff line number Diff line
@@ -21,6 +21,9 @@ 
#include <stdint.h>

#include <sys/types.h>



#include <string>

#include <string_view>



#include <android-base/logging.h>

#include <android-base/unique_fd.h>
@@ -94,7 +97,7 @@ bool UpdatePartitionName(LpMetadataPartition* partition, const std::string& name 
// Call BLKROSET ioctl on fd so that fd is readonly / read-writable.

bool SetBlockReadonly(int fd, bool readonly);



::android::base::unique_fd GetControlFileOrOpen(const char* path, int flags);

::android::base::unique_fd GetControlFileOrOpen(std::string_view path, int flags);



// For Virtual A/B updates, modify |metadata| so that it can be written to |target_slot_number|.

bool UpdateMetadataForInPlaceSnapshot(LpMetadata* metadata, uint32_t source_slot_number,