libbpf: auto-resize relocatable LOAD/STORE instructions #153
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…O-RE
Add support for patching instructions of the following form:
- rX = *(T *)(rY + <off>);
- *(T *)(rX + <off>) = rY;
- *(T *)(rX + <off>) = <imm>, where T is one of {u8, u16, u32, u64}.
For such instructions, if the actual kernel field recorded in CO-RE relocation
has a different size than the one recorded locally (e.g., from vmlinux.h),
then libbpf will adjust T to an appropriate 1-, 2-, 4-, or 8-byte loads.
In general, such transformation is not always correct and could lead to
invalid final value being loaded or stored. But two classes of cases are
always safe:
- if both local and target (kernel) types are unsigned integers, but of
different sizes, then it's OK to adjust load/store instruction according to
the necessary memory size. Zero-extending nature of such instructions and
unsignedness make sure that the final value is always correct;
- pointer size mismatch between BPF target architecture (which is always
64-bit) and 32-bit host kernel architecture can be similarly resolved
automatically, because pointer is essentially an unsigned integer. Loading
32-bit pointer into 64-bit BPF register with zero extension will leave
correct pointer in the register.
Both cases are necessary to support CO-RE on 32-bit kernels, as `unsigned
long` in vmlinux.h generated from 32-bit kernel is 32-bit, but when compiled
with BPF program for BPF target it will be treated by compiler as 64-bit
integer. Similarly, pointers in vmlinux.h are 32-bit for kernel, but treated
as 64-bit values by compiler for BPF target. Both problems are now resolved by
libbpf for direct memory reads.
But similar transformations are useful in general when kernel fields are
"resized" from, e.g., unsigned int to unsigned long (or vice versa).
Now, similar transformations for signed integers are not safe to perform as
they will result in incorrect sign extension of the value. If such situation
is detected, libbpf will emit helpful message and will poison the instruction.
Not failing immediately means that it's possible to guard the instruction
based on kernel version (or other conditions) and make sure it's not
reachable.
If there is a need to read signed integers that change sizes between different
kernels, it's possible to use BPF_CORE_READ_BITFIELD() macro, which works both
with bitfields and non-bitfield integers of any signedness and handles
sign-extension properly. Also, bpf_core_read() with proper size and/or use of
bpf_core_field_size() relocation could allow to deal with such complicated
situations explicitly, if not so conventiently as direct memory reads.
Selftests added in a separate patch in progs/test_core_autosize.c demonstrate
both direct memory and probed use cases.
BPF_CORE_READ() is not changed and it won't deal with such situations as
automatically as direct memory reads due to the signedness integer
limitations, which are much harder to detect and control with compiler macro
magic. So it's encouraged to utilize direct memory reads as much as possible.
Signed-off-by: Andrii Nakryiko <[email protected]>
Use generalized BTF parsing logic, making it possible to parse BTF both from ELF file, as well as a raw BTF dump. This makes it easier to write custom tests with manually generated BTFs. Signed-off-by: Andrii Nakryiko <[email protected]>
Add selftests validating libbpf's auto-resizing of load/store instructions when used with CO-RE relocations. An explicit and manual approach with using bpf_core_read() is also demonstrated and tested. Separate BPF program is supposed to fail due to using signed integers of sizes that differ from kernel's sizes. To reliably simulate 32-bit BTF (i.e., the one with sizeof(long) == sizeof(void *) == 4), selftest generates its own custom BTF and passes it as a replacement for real kernel BTF. This allows to test 32/64-bitness mix on all architectures. Signed-off-by: Andrii Nakryiko <[email protected]>
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At least one diff in series https://patchwork.kernel.org/project/bpf/list/?series=358607 irrelevant now. Closing PR. |
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. Thanks for Eduard providing the libbpf_probe_func_many test case. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED ./test_progs -t libbpf_probe_kfuncs_many #154 libbpf_probe_kfuncs_many:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Co-developed-by: Eduard Zingerman <[email protected]> Signed-off-by: Eduard Zingerman <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. Thanks for Eduard providing the libbpf_probe_func_many test case. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED ./test_progs -t libbpf_probe_kfuncs_many #154 libbpf_probe_kfuncs_many:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Co-developed-by: Eduard Zingerman <[email protected]> Signed-off-by: Eduard Zingerman <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. Thanks for Eduard providing the libbpf_probe_func_many test case. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED ./test_progs -t libbpf_probe_kfuncs_many #154 libbpf_probe_kfuncs_many:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Co-developed-by: Eduard Zingerman <[email protected]> Signed-off-by: Eduard Zingerman <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Reviewed-by: Eduard Zingerman <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Reviewed-by: Eduard Zingerman <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Reviewed-by: Eduard Zingerman <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Add selftests for prog_kfunc feature probing. ./test_progs -t libbpf_probe_kfuncs #153 libbpf_probe_kfuncs:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Cc: Tao Chen <[email protected]> Reviewed-by: Jiri Olsa <[email protected]> Reviewed-by: Eduard Zingerman <[email protected]> Signed-off-by: Tao Chen <[email protected]>
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Pull request for series with
subject: libbpf: auto-resize relocatable LOAD/STORE instructions
version: 1
url: https://patchwork.kernel.org/project/bpf/list/?series=358607