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Use androidboot.partition_map as a fallback for matching partition names in the preinit finding. #8293

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merged 4 commits into from
Aug 15, 2024
Merged

Use androidboot.partition_map as a fallback for matching partition names in the preinit finding. #8293

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0205294
Use `androidboot.partition_map` as a fallback for matching partition …
chsbuffer Aug 7, 2024
1b74448
Use parse_impl for partition_map
yujincheng08 Aug 8, 2024
65b6112
Use find_if
yujincheng08 Aug 8, 2024
28be995
load `partition_map` only once
yujincheng08 Aug 13, 2024
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34 changes: 28 additions & 6 deletions native/src/init/getinfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -41,16 +41,16 @@ static string extract_quoted_str_until(chars<escapes...>, chars<breaks...>,
}

// Parse string into key value pairs.
// The string format: [delim][key][padding]=[padding][value][delim]
template<char delim, char... padding>
// The string format: [delim][key][padding][eq][padding][value][delim]
template<char delim, char eq, char... padding>
static kv_pairs parse_impl(chars<padding...>, string_view str) {
kv_pairs kv;
char skip_array[] = {'=', padding...};
char skip_array[] = {eq, padding...};
string_view skip(skip_array, std::size(skip_array));
bool quoted = false;
for (size_t pos = 0u; pos < str.size(); pos = str.find_first_not_of(delim, pos)) {
auto key = extract_quoted_str_until(
chars<padding..., delim>{}, chars<'='>{}, str, pos, quoted);
chars<padding..., delim>{}, chars<eq>{}, str, pos, quoted);
pos = str.find_first_not_of(skip, pos);
if (pos == string_view::npos || str[pos] == delim) {
kv.emplace_back(key, "");
Expand All @@ -63,10 +63,13 @@ static kv_pairs parse_impl(chars<padding...>, string_view str) {
}

static kv_pairs parse_cmdline(string_view str) {
return parse_impl<' '>(chars<>{}, str);
return parse_impl<' ', '='>(chars<>{}, str);
}
static kv_pairs parse_bootconfig(string_view str) {
return parse_impl<'\n'>(chars<' '>{}, str);
return parse_impl<'\n', '='>(chars<' '>{}, str);
}
static kv_pairs parse_partition_map(std::string_view str) {
return parse_impl<';', ','>(chars<>{}, str);
}

#define test_bit(bit, array) (array[bit / 8] & (1 << (bit % 8)))
Expand Down Expand Up @@ -207,6 +210,25 @@ void load_kernel_info(BootConfig *config) {
config->print();
}

// `androidboot.partition_map` allows associating a partition name for a raw block device
// through a comma separated and semicolon deliminated list. For example,
// `androidboot.partition_map=vdb,metadata;vdc,userdata` maps `vdb` to `metadata` and `vdc` to
// `userdata`.
// https://android.googlesource.com/platform/system/core/+/refs/heads/android13-release/init/devices.cpp#191

kv_pairs load_partition_map() {
const string_view kPartitionMapKey = "androidboot.partition_map";
for (const auto &[key, value] : parse_cmdline(full_read("/proc/cmdline"))) {
if (key == kPartitionMapKey)
return parse_partition_map(value);
}
for (const auto &[key, value] : parse_bootconfig(full_read("/proc/bootconfig"))) {
if (key == kPartitionMapKey)
return parse_partition_map(value);
}
return {};
}

bool check_two_stage() {
if (access("/apex", F_OK) == 0)
return true;
Expand Down
1 change: 1 addition & 0 deletions native/src/init/init.hpp
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Expand Up @@ -29,6 +29,7 @@ extern std::vector<std::string> mount_list;
int magisk_proxy_main(int argc, char *argv[]);
bool unxz(out_stream &strm, rust::Slice<const uint8_t> bytes);
void load_kernel_info(BootConfig *config);
kv_pairs load_partition_map();
bool check_two_stage();
const char *backup_init();
void restore_ramdisk_init();
Expand Down
21 changes: 15 additions & 6 deletions native/src/init/mount.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -29,21 +29,23 @@ bool avd_hack = false;
static void parse_device(devinfo *dev, const char *uevent) {
dev->partname[0] = '\0';
dev->devpath[0] = '\0';
dev->dmname[0] = '\0';
dev->devname[0] = '\0';
parse_prop_file(uevent, [=](string_view key, string_view value) -> bool {
if (key == "MAJOR")
dev->major = parse_int(value.data());
else if (key == "MINOR")
dev->minor = parse_int(value.data());
else if (key == "DEVNAME")
strcpy(dev->devname, value.data());
strscpy(dev->devname, value.data(), sizeof(dev->devname));
else if (key == "PARTNAME")
strcpy(dev->partname, value.data());
strscpy(dev->partname, value.data(), sizeof(dev->devname));
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Is it intentional that this is using sizeof(dev->devname) instead of sizeof(dev->partname)? Might be irrelevant, I'm not exactly sure how this code is called, I just happened to glance at it the other day.

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@chsbuffer chsbuffer Aug 29, 2024 •
edited
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It doesn't really matter, partname and devname are both 32.
@yujincheng08 Can you answer whether this is intentional or not?

I'm also worried that strscpy doesn't add zero terminators, maybe we should use strncat(dst, src, buffer_size - 1) or use strncasecmp instead of strcastcmp when comparing.


return true;
});
}

static void collect_devices() {
static void collect_devices(const auto &partition_map) {
char path[PATH_MAX];
devinfo dev{};
if (auto dir = xopen_dir("/sys/dev/block"); dir) {
Expand All @@ -55,7 +57,13 @@ static void collect_devices() {
sprintf(path, "/sys/dev/block/%s/dm/name", entry->d_name);
if (access(path, F_OK) == 0) {
auto name = rtrim(full_read(path));
strcpy(dev.dmname, name.data());
strscpy(dev.dmname, name.data(), sizeof(dev.dmname));
}
if (auto it = std::ranges::find_if(partition_map, [&](const auto &i) {
return i.first == dev.devname;
}); dev.partname[0] == '\0' && it != partition_map.end()) {
// use androidboot.partition_map as partname fallback.
strscpy(dev.partname, it->second.data(), sizeof(dev.partname));
}
sprintf(path, "/sys/dev/block/%s", entry->d_name);
xrealpath(path, dev.devpath, sizeof(dev.devpath));
Expand All @@ -70,8 +78,9 @@ static struct {
} blk_info;

static dev_t setup_block() {
const auto partition_map = load_partition_map();
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if (dev_list.empty())
collect_devices();
collect_devices(partition_map);

for (int tries = 0; tries < 3; ++tries) {
for (auto &dev : dev_list) {
Expand All @@ -93,7 +102,7 @@ static dev_t setup_block() {
// Wait 10ms and try again
usleep(10000);
dev_list.clear();
collect_devices();
collect_devices(partition_map);
}

// The requested partname does not exist
Expand Down