On Thu, Feb 10, 2022 at 2:18 PM Yonghong Song <yhs@xxxxxx> wrote:
>
>
>
> On 2/9/22 4:36 PM, Delyan Kratunov wrote:
> > As reported in [0], kernel and userspace can sometimes disagree
> > on the definition of a typedef (in particular, the size).
> > This leads to trouble when userspace maps the memory of a bpf program
> > and reads/writes to it assuming a different memory layout.
> >
> > This series resolves most int-like typedefs and rewrites them as
> > standard int16_t-like types. In particular, we don't touch
> > __u32-like types, char, and _Bool, as changing them changes cast
> > semantics and would break too many pre-existing programs. For example,
> > int8_t* is not convertible to char* because int8_t is explicitly signed.
>
> Build with clang (adding LLVM=1 to build kernel and selftests),
> several btf_dump subtests failed. Please take a look.
>
> btf_dump_data:PASS:find type id 0 nsec
> btf_dump_data:PASS:failed/unexpected type_sz 0 nsec
> btf_dump_data:FAIL:ensure expected/actual match unexpected ensure
> expected/actual match: actual '(int32_t)1234' != expected '(int)1234'
> btf_dump_data:PASS:find type id 0 nsec
> btf_dump_data:PASS:failed/unexpected type_sz 0 nsec
> btf_dump_data:PASS:ensure expected/actual match 0 nsec
> btf_dump_data:PASS:find type id 0 nsec
> btf_dump_data:PASS:failed/unexpected type_sz 0 nsec
> btf_dump_data:FAIL:ensure expected/actual match unexpected ensure
> expected/actual match: actual '(int32_t)1234' != expected '(int)1234'
> btf_dump_data:PASS:find type id 0 nsec
> btf_dump_data:PASS:failed/unexpected type_sz 0 nsec
> btf_dump_data:FAIL:ensure expected/actual match unexpected ensure
> expected/actual match: actual '(int32_t)0' != expected '(int)0'
> ...
> btf_dump_data:FAIL:ensure expected/actual match unexpected ensure
> expected/actual match: actual '(uint128_t)0xffffffffffffffff' !=
> expected '(unsigned __int128)0xffffffffffffffff'
> btf_dump_data:PASS:find type id 0 nsec
> btf_dump_data:PASS:failed/unexpected type_sz 0 nsec
> btf_dump_data:FAIL:ensure expected/actual match unexpected ensure
> expected/actual match: actual
> '(uint128_t)0xfffffffffffffffffffffffffffffffe' != expected '(unsigned
> __int128)0xfffffffffffffffffffffffffffff'
> test_btf_dump_int_data:FAIL:dump unsigned __int128 unexpected error: -14
> (errno 7)
> #20/9 btf_dump/btf_dump: int_data:FAIL
> ...
> btf_dump_data:FAIL:ensure expected/actual match unexpected ensure
> expected/actual match: actual '(uint64_t)1' != expected '(u64)1'
> btf_dump_data:PASS:find type id 0 nsec
> btf_dump_data:PASS:failed/unexpected type_sz 0 nsec
> btf_dump_data:FAIL:ensure expected/actual match unexpected ensure
> expected/actual match: actual '(uint64_t)0' != expected '(u64)0'
> btf_dump_data:PASS:find type id 0 nsec
> ...
> btf_dump_data:FAIL:ensure expected/actual match unexpected ensure
> expected/actual match: actual '(atomic_t){
> .counter = (int32_t)0,
> }' != expected '(atomic_t){
> .counter = (int)0,
> }'
> btf_dump_data:PASS:find type id 0 nsec
> btf_dump_data:PASS:failed to return -E2BIG 0 nsec
> btf_dump_data:PASS:ensure expected/actual match 0 nsec
> #20/12 btf_dump/btf_dump: typedef_data:FAIL
> ...
> test_btf_dump_struct_data:FAIL:file_operations unexpected
> file_operations: actual '(struct file_operations){
> .owner = (struct module *)0xffffffffffffffff,
> .llseek = (int64_t (*)(struct file *, int64_t,
> int32_t))0xfffffffffff' != expected '(struct file_operations){
> .owner = (struct module *)0xffffffffffffffff,
> .llseek = (loff_t (*)(struct file *, loff_t,
> int))0xffffffffffffffff,'
> ...
> ...
>
This is due to unconditional normalization in
btf_dump_emit_type_cast(), we shouldn't do it. So this will "autofix"
itself when we fix that issue.
> >
> > [0]: https://github.com/iovisor/bcc/pull/3777
> >
> > Delyan Kratunov (3):
> > libbpf: btf_dump can produce explicitly sized ints
> > bpftool: skeleton uses explicitly sized ints
> > selftests/bpf: add test case for userspace and bpf type size mismatch
> >
> > tools/bpf/bpftool/gen.c | 3 +
> > tools/lib/bpf/btf.h | 4 +-
> > tools/lib/bpf/btf_dump.c | 80 ++++++++++++++++++-
> > .../selftests/bpf/prog_tests/skeleton.c | 22 +++--
> > .../selftests/bpf/progs/test_skeleton.c | 8 ++
> > 5 files changed, 107 insertions(+), 10 deletions(-)
> >
> > --
> > 2.34.1
