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,'
...
...
[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
