| Message ID | 20230301184026.800691-4-deso@posteo.net (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | Make uprobe attachment APK aware | expand |
On Wed, Mar 1, 2023 at 10:40 AM Daniel Müller <deso@posteo.net> 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@posteo.net> > --- > tools/lib/bpf/libbpf.c | 92 ++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 85 insertions(+), 7 deletions(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 4543e9..e6b99a 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 +10703,69 @@ 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; > + int err; > + Elf *elf; > + > + archive = zip_archive_open(archive_path); > + if (IS_ERR(archive)) { Unfortunately, this won't work with the libbpf_err_ptr() approach that you used inside zip_archive_open(). Since libbpf v1.0 libbpf_err_ptr() will return NULL on error (and so this IS_ERR() check will always be false, and subsequent PTR_ERR() would be returning 0) and only set errno to actual error. This was meant to be used mostly for user-facing APIs. Given zip_archive_open() is internal, explicit PTR_ERR() use as you do below makes most sense. Please update and respin. > + pr_warn("zip: failed to open %s: %ld\n", archive_path, PTR_ERR(archive)); > + return PTR_ERR(archive); err = PTR_ERR(archive); and use err in pr_warn() and return? and it's not clear why you need both ret and err, it should be fine to just use ret (long vs int doesn't hurt error propagation) > + } > + > + err = zip_archive_find_entry(archive, file_name, &entry); > + if (err) { > + pr_warn("zip: could not find archive member %s in %s: %d\n", file_name, > + archive_path, err); > + ret = err; > + goto out; > + } > + pr_debug("zip: found entry for %s in %s at 0x%lx\n", file_name, archive_path, > + (unsigned long)entry.data_offset); > + [...]
On Wed, Mar 01, 2023 at 11:31:09AM -0800, Andrii Nakryiko wrote: > On Wed, Mar 1, 2023 at 10:40 AM Daniel Müller <deso@posteo.net> 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@posteo.net> > > --- > > tools/lib/bpf/libbpf.c | 92 ++++++++++++++++++++++++++++++++++++++---- > > 1 file changed, 85 insertions(+), 7 deletions(-) > > > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > > index 4543e9..e6b99a 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 +10703,69 @@ 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; > > + int err; > > + Elf *elf; > > + > > + archive = zip_archive_open(archive_path); > > + if (IS_ERR(archive)) { > > Unfortunately, this won't work with the libbpf_err_ptr() approach that > you used inside zip_archive_open(). Since libbpf v1.0 libbpf_err_ptr() > will return NULL on error (and so this IS_ERR() check will always be > false, and subsequent PTR_ERR() would be returning 0) and only set > errno to actual error. This was meant to be used mostly for > user-facing APIs. Thanks for pointing that out. > Given zip_archive_open() is internal, explicit PTR_ERR() use as you do > below makes most sense. Please update and respin. Sure. > > + pr_warn("zip: failed to open %s: %ld\n", archive_path, PTR_ERR(archive)); > > + return PTR_ERR(archive); > > err = PTR_ERR(archive); and use err in pr_warn() and return? > > and it's not clear why you need both ret and err, it should be fine to > just use ret (long vs int doesn't hurt error propagation) Changed. Thanks, Daniel
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 4543e9..e6b99a 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 +10703,69 @@ 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; + int err; + Elf *elf; + + archive = zip_archive_open(archive_path); + if (IS_ERR(archive)) { + pr_warn("zip: failed to open %s: %ld\n", archive_path, PTR_ERR(archive)); + return PTR_ERR(archive); + } + + err = zip_archive_find_entry(archive, file_name, &entry); + if (err) { + pr_warn("zip: could not find archive member %s in %s: %d\n", file_name, + archive_path, err); + ret = err; + 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; + } + + elf = elf_memory((void *)entry.data, entry.data_length); + if (!elf) { + pr_warn("elf: could not read elf file %s from %s: %s\n", file_name, archive_path, + elf_errmsg(-1)); + ret = -LIBBPF_ERRNO__LIBELF; + goto out; + } + + ret = elf_find_func_offset(elf, file_name, func_name); + if (ret > 0) { + pr_debug("elf: symbol address match for %s of %s in %s: 0x%x + 0x%lx = 0x%lx\n", + func_name, file_name, archive_path, entry.data_offset, ret, + ret + entry.data_offset); + ret += entry.data_offset; + } + elf_end(elf); + +out: + zip_archive_close(archive); + return ret; +} + static const char *arch_specific_lib_paths(void) { /* @@ -10787,9 +10851,10 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, const char *binary_path, size_t func_offset, const struct bpf_uprobe_opts *opts) { - DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts); + const char *archive_path = NULL, *archive_sep = NULL; char errmsg[STRERR_BUFSIZE], *legacy_probe = NULL; - char full_binary_path[PATH_MAX]; + DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts); + char full_path[PATH_MAX]; struct bpf_link *link; size_t ref_ctr_off; int pfd, err; @@ -10806,21 +10871,34 @@ 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, + min(sizeof(full_path), (size_t)(archive_sep - binary_path + 1))); + 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); } - binary_path = full_binary_path; + binary_path = full_path; } func_name = OPTS_GET(opts, func_name, NULL); if (func_name) { long sym_off; - sym_off = elf_find_func_offset_from_file(binary_path, func_name); + if (archive_path) { + sym_off = elf_find_func_offset_from_archive(archive_path, binary_path, + func_name); + binary_path = archive_path; + } else { + sym_off = elf_find_func_offset_from_file(binary_path, func_name); + } if (sym_off < 0) return libbpf_err_ptr(sym_off); func_offset += sym_off;
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@posteo.net> --- tools/lib/bpf/libbpf.c | 92 ++++++++++++++++++++++++++++++++++++++---- 1 file changed, 85 insertions(+), 7 deletions(-)