Skip to content

Commit

Permalink
Fix crash with big apks on assembly registration
Browse files Browse the repository at this point in the history 
Xamarin.Android, on launch, needs to do a pass through the files in the apk to register assemblies (.dll/.exe), dll configuration files (.config), symbols (.mdb/.pdb) and bindings typemaps (.jm/.mj). To do this pass, the process was to mmap the apk in the process' adress space, then grab the memory offsets for each file and register them on each system as needed. However, mmap-ing the whole apk has the consequence of taking potentially a lot of adress space. Considering it is legal to have a big apk (even though you can't submit an apk of more than 100 Mb to the Play Store, you can still submit it somewhere else, or embed your data in the apk during the development process for simplicity's sake), having an apk of about ~800 Mb in size automatically crashes on launch in armeabi-v7a because it can't find a contiguous 800 Mb block of adress space. The following log is usually found when that issue hits:
`I/monodroid-assembly(14915): start: 0xffffffff end: 0x3da16747 len: 1033987912 apk: /data/app/<package_name>-1/base.apk`
However, we don't need to mmap the whole apk, only the files that we are actually registering. Therefore, refactor the registration code to not mmap the whole apk. Instead, open the apk regularly, then when we actually need one of the entries, mmap the area of the file in the apk from a page-aligned offset and use those mmap sections for registration instead.
Fixes dotnet#1673
  • Loading branch information
@mathieubourgeois
mathieubourgeois committed Dec 24, 2018
1 parent 95f143f commit 28e971c
Showing 1 changed file with 58 additions and 42 deletions.
100 changes: 58 additions & 42 deletions src/monodroid/jni/embedded-assemblies.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -243,6 +243,35 @@ struct md_mmap_info {
size_t size;
};

struct md_apk_mmap_info {
md_mmap_info mmap_info;
md_mmap_info file_info;
};

MONO_API int monodroid_getpagesize (void);

static md_apk_mmap_info
md_mmap_apk_file(int fd, uLong offset, uLong size, const char* filename, const char* apk)
{
md_apk_mmap_info info;

int pageSize = monodroid_getpagesize();
uLong offsetFromPage = offset % pageSize;
uLong offsetPage = offset - offsetFromPage;
uLong offsetSize = size + offsetFromPage;

info.mmap_info.area = mmap(NULL, offsetSize, PROT_READ, MAP_PRIVATE, fd, offsetPage);
info.mmap_info.size = offsetSize;
info.file_info.area = (void*)((const char*)info.mmap_info.area + offsetFromPage);
info.file_info.size = size;

log_info (LOG_ASSEMBLY, " mmap_start: %08p mmap_end: %08p mmap_len: % 12u file_start: %08p file_end: %08p file_len: % 12u apk: %s file: %s",
info.mmap_info.area, reinterpret_cast<int*> (info.mmap_info.area) + info.mmap_info.size, (unsigned int) info.mmap_info.size,
info.file_info.area, reinterpret_cast<int*> (info.file_info.area) + info.file_info.size, (unsigned int) info.file_info.size, apk, filename);

return info;
}

static void*
md_mmap_open_file (void *opaque, const char *filename, int mode)
{
Expand All @@ -254,37 +283,31 @@ md_mmap_open_file (void *opaque, const char *filename, int mode)
static uLong
md_mmap_read_file (void *opaque, void *stream, void *buf, uLong size)
{
int *offset = reinterpret_cast<int*> (stream);
struct md_mmap_info *info = reinterpret_cast <md_mmap_info*> (opaque);

memcpy (buf, ((const char*) info->area) + *offset, size);
*offset += size;

return size;
int fd = *reinterpret_cast<int*>(opaque);
return read(fd, buf, size);
}

static long
md_mmap_tell_file (void *opaque, void *stream)
{
int *offset = reinterpret_cast <int*> (stream);
return *offset;
int fd = *reinterpret_cast<int*>(opaque);
return lseek(fd, 0, SEEK_CUR);
}

static long
md_mmap_seek_file (void *opaque, void *stream, uLong offset, int origin)
{
int *pos = reinterpret_cast <int*> (stream);
struct md_mmap_info *info = reinterpret_cast <md_mmap_info*> (opaque);
int fd = *reinterpret_cast<int*>(opaque);

switch (origin) {
case ZLIB_FILEFUNC_SEEK_END:
*pos = info->size;
/* goto case ZLIB_FILEFUNC_SEEK_CUR */
lseek(fd, offset, SEEK_END);
break;
case ZLIB_FILEFUNC_SEEK_CUR:
*pos += (int) offset;
lseek(fd, offset, SEEK_CUR);
break;
case ZLIB_FILEFUNC_SEEK_SET:
*pos = (int) offset;
lseek(fd, offset, SEEK_SET);
break;
default:
return -1;
Expand Down Expand Up @@ -351,8 +374,6 @@ gather_bundled_assemblies_from_apk (
int *bundle_count)
{
int fd;
struct stat buf;
struct md_mmap_info mmap_info;
unzFile file;

zlib_filefunc_def funcs = {
Expand All @@ -371,21 +392,8 @@ gather_bundled_assemblies_from_apk (
// TODO: throw
return -1;
}
if (fstat (fd, &buf) < 0) {
close (fd);
// TODO: throw
return -1;
}

mmap_info.area = mmap (NULL, buf.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
mmap_info.size = buf.st_size;

log_info (LOG_ASSEMBLY, " start: %08p end: %08p len: % 12u apk: %s",
mmap_info.area, reinterpret_cast<int*> (mmap_info.area) + mmap_info.size, (unsigned int) mmap_info.size, apk);

close (fd);

funcs.opaque = &mmap_info;
funcs.opaque = &fd;

if ((file = unzOpen2 (NULL, &funcs)) != NULL) {
do {
Expand All @@ -405,11 +413,13 @@ gather_bundled_assemblies_from_apk (
}

if (utils.ends_with (cur_entry_name, ".jm")) {
add_type_mapping (&java_to_managed_maps, apk, cur_entry_name, ((const char*) mmap_info.area) + offset);
md_apk_mmap_info map_info = md_mmap_apk_file(fd, offset, info.uncompressed_size, cur_entry_name, apk);
add_type_mapping (&java_to_managed_maps, apk, cur_entry_name, (const char*)map_info.file_info.area);
continue;
}
if (utils.ends_with (cur_entry_name, ".mj")) {
add_type_mapping (&managed_to_java_maps, apk, cur_entry_name, ((const char*) mmap_info.area) + offset);
md_apk_mmap_info map_info = md_mmap_apk_file(fd, offset, info.uncompressed_size, cur_entry_name, apk);
add_type_mapping (&managed_to_java_maps, apk, cur_entry_name, (const char*)map_info.file_info.area);
continue;
}

Expand All @@ -420,7 +430,7 @@ gather_bundled_assemblies_from_apk (
// assemblies must be 4-byte aligned, or Bad Things happen
if ((offset & 0x3) != 0) {
log_fatal (LOG_ASSEMBLY, "Assembly '%s' is located at a bad address %p\n", cur_entry_name,
((const unsigned char*) mmap_info.area) + offset);
offset);
log_fatal (LOG_ASSEMBLY, "You MUST run `zipalign` on %s\n", strrchr (apk, '/') + 1);
exit (FATAL_EXIT_MISSING_ZIPALIGN);
}
Expand All @@ -431,19 +441,22 @@ gather_bundled_assemblies_from_apk (
if ((utils.ends_with (cur_entry_name, ".mdb") || utils.ends_with (cur_entry_name, ".pdb")) &&
register_debug_symbols &&
!entry_is_overridden &&
*bundle != NULL &&
register_debug_symbols_for_assembly (mono, cur_entry_name, (*bundle) [*bundle_count-1],
((const mono_byte*) mmap_info.area) + offset,
info.uncompressed_size))
continue;
*bundle != NULL) {
md_apk_mmap_info map_info = md_mmap_apk_file(fd, offset, info.uncompressed_size, cur_entry_name, apk);
if(register_debug_symbols_for_assembly (mono, cur_entry_name, (*bundle) [*bundle_count-1],
(const mono_byte*)map_info.file_info.area,
info.uncompressed_size))
continue;
}

if (utils.ends_with (cur_entry_name, ".config") &&
*bundle != NULL) {
char *assembly_name = utils.monodroid_strdup_printf ("%s", basename (cur_entry_name));
// Remove '.config' suffix
*strrchr (assembly_name, '.') = '\0';

mono->register_config_for_assembly (assembly_name, ((const char*) mmap_info.area) + offset);

md_apk_mmap_info map_info = md_mmap_apk_file(fd, offset, info.uncompressed_size, cur_entry_name, apk);
mono->register_config_for_assembly (assembly_name, (const char*)map_info.file_info.area);

continue;
}
Expand All @@ -458,8 +471,9 @@ gather_bundled_assemblies_from_apk (
cur = (*bundle) [*bundle_count] = reinterpret_cast<MonoBundledAssembly*> (utils.xcalloc (1, sizeof (MonoBundledAssembly)));
++*bundle_count;

md_apk_mmap_info map_info = md_mmap_apk_file(fd, offset, info.uncompressed_size, cur_entry_name, apk);
cur->name = utils.monodroid_strdup_printf ("%s", strstr (cur_entry_name, prefix) + strlen (prefix));
cur->data = ((const unsigned char*) mmap_info.area) + offset;
cur->data = (const unsigned char*)map_info.file_info.area;

// MonoBundledAssembly::size is const?!
psize = (unsigned int*) &cur->size;
Expand All @@ -483,6 +497,8 @@ gather_bundled_assemblies_from_apk (
} while (unzGoToNextFile (file) == UNZ_OK);
unzClose (file);
}

close(fd);

return 0;
}
Expand Down

0 comments on commit 28e971c

Please sign in to comment.