On Tue, Feb 21, 2023 at 3:45 PM Daniel Müller <deso@xxxxxxxxxx> wrote: > > This change adds support for attaching uprobes to shared objects located > in APKs, which is relevant for Android systems where various libraries > may reside in APKs. To make that happen, we extend the syntax for the > "binary path" argument to attach to with that supported by various > Android tools: > <archive>!/<binary-in-archive> > > For example: > /system/app/test-app/test-app.apk!/lib/arm64-v8a/libc++_shared.so > > APKs need to be specified via full path, i.e., we do not attempt to > resolve mere file names by searching system directories. > > We cannot currently test this functionality end-to-end in an automated > fashion, because it relies on an Android system being present, but there > is no support for that in CI. I have tested the functionality manually, > by creating a libbpf program containing a uretprobe, attaching it to a > function inside a shared object inside an APK, and verifying the sanity > of the returned values. > > Signed-off-by: Daniel Müller <deso@xxxxxxxxxx> > --- > tools/lib/bpf/libbpf.c | 87 ++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 80 insertions(+), 7 deletions(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 4543e9..a41993b 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -53,6 +53,7 @@ > #include "libbpf_internal.h" > #include "hashmap.h" > #include "bpf_gen_internal.h" > +#include "zip.h" > > #ifndef BPF_FS_MAGIC > #define BPF_FS_MAGIC 0xcafe4a11 > @@ -10702,6 +10703,65 @@ static long elf_find_func_offset_from_file(const char *binary_path, const char * > return ret; > } > > +/* Find offset of function name in archive specified by path. Currently > + * supported are .zip files that do not compress their contents, as used on > + * Android in the form of APKs, for example. "file_name" is the name of the ELF > + * file inside the archive. "func_name" matches symbol name or name@@LIB for > + * library functions. > + * > + * An overview of the APK format specifically provided here: > + * https://en.wikipedia.org/w/index.php?title=Apk_(file_format)&oldid=1139099120#Package_contents > + */ > +static long elf_find_func_offset_from_archive(const char *archive_path, const char *file_name, > + const char *func_name) > +{ > + struct zip_archive *archive; > + struct zip_entry entry; > + long ret = -ENOENT; > + Elf *elf; > + > + archive = zip_archive_open(archive_path); > + if (!archive) { > + pr_warn("zip: failed to open %s\n", archive_path); > + return -LIBBPF_ERRNO__FORMAT; we don't preserve errno inside zip_archive_open, it might be useful, though, because there is a difference between "file not found", "file has invalid format", "we don't have permission", which is where errno comes in handy > + } > + > + if (zip_archive_find_entry(archive, file_name, &entry)) { > + pr_warn("zip: could not find archive member %s in %s\n", file_name, archive_path); > + ret = -LIBBPF_ERRNO__FORMAT; let's preserve error code returned from zip_archive_find_entry and log it in above pr_warn. It's not always format problem, requested binary/library might be just missing from APK > + goto out; > + } > + pr_debug("zip: found entry for %s in %s at 0x%lx\n", file_name, archive_path, > + (unsigned long)entry.data_offset); > + > + if (entry.compression) { > + pr_warn("zip: entry %s of %s is compressed and cannot be handled\n", file_name, > + archive_path); > + ret = -LIBBPF_ERRNO__FORMAT; > + goto out; > + } > + [...] > @@ -10806,21 +10867,33 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, > if (!binary_path) > return libbpf_err_ptr(-EINVAL); > > - if (!strchr(binary_path, '/')) { > - err = resolve_full_path(binary_path, full_binary_path, > - sizeof(full_binary_path)); > + /* Check if "binary_path" refers to an archive. */ > + archive_sep = strstr(binary_path, "!/"); > + if (archive_sep) { > + full_path[0] = '\0'; > + libbpf_strlcpy(full_path, binary_path, archive_sep - binary_path + 1); that's probably the bug you mentioned offline, should be sizeof(full_path) for the third arg, right? > + archive_path = full_path; > + binary_path = archive_sep + 2; > + } else if (!strchr(binary_path, '/')) { > + err = resolve_full_path(binary_path, full_path, sizeof(full_path)); > if (err) { > pr_warn("prog '%s': failed to resolve full path for '%s': %d\n", > prog->name, binary_path, err); > return libbpf_err_ptr(err); > } [...]
