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Commit Graph

Author	SHA1	Message	Date
Jean-Philippe Brucker	3615bdf6d9	selftests/bpf: Fix "dubious pointer arithmetic" test The verifier trace changed following a bugfix. After checking the 64-bit sign, only the upper bit mask is known, not bit 31. Update the test accordingly. Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> Acked-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>	2020-12-10 13:11:30 -08:00
Alexei Starovoitov	75748837b7	bpf: Propagate scalar ranges through register assignments. The llvm register allocator may use two different registers representing the same virtual register. In such case the following pattern can be observed: 1047: (bf) r9 = r6 1048: (a5) if r6 < 0x1000 goto pc+1 1050: ... 1051: (a5) if r9 < 0x2 goto pc+66 1052: ... 1053: (bf) r2 = r9 /* r2 needs to have upper and lower bounds */ This is normal behavior of greedy register allocator. The slides 137+ explain why regalloc introduces such register copy: http://llvm.org/devmtg/2018-04/slides/Yatsina-LLVM%20Greedy%20Register%20Allocator.pdf There is no way to tell llvm 'not to do this'. Hence the verifier has to recognize such patterns. In order to track this information without backtracking allocate ID for scalars in a similar way as it's done for find_good_pkt_pointers(). When the verifier encounters r9 = r6 assignment it will assign the same ID to both registers. Later if either register range is narrowed via conditional jump propagate the register state into the other register. Clear register ID in adjust_reg_min_max_vals() for any alu instruction. The register ID is ignored for scalars in regsafe() and doesn't affect state pruning. mark_reg_unknown() clears the ID. It's used to process call, endian and other instructions. Hence ID is explicitly cleared only in adjust_reg_min_max_vals() and in 32-bit mov. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20201009011240.48506-2-alexei.starovoitov@gmail.com	2020-10-09 22:03:06 +02:00
Stanislav Fomichev	3b09d27cc9	selftests/bpf: Move test_align under test_progs There is a much higher chance we can see the regressions if the test is part of test_progs. Signed-off-by: Stanislav Fomichev <sdf@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20200515194904.229296-2-sdf@google.com	2020-05-16 01:18:14 +02:00

Author

SHA1

Message

Date

Jean-Philippe Brucker

3615bdf6d9

selftests/bpf: Fix "dubious pointer arithmetic" test

The verifier trace changed following a bugfix. After checking the 64-bit
sign, only the upper bit mask is known, not bit 31. Update the test
accordingly.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2020-12-10 13:11:30 -08:00

Alexei Starovoitov

75748837b7

bpf: Propagate scalar ranges through register assignments.

The llvm register allocator may use two different registers representing the
same virtual register. In such case the following pattern can be observed:
1047: (bf) r9 = r6
1048: (a5) if r6 < 0x1000 goto pc+1
1050: ...
1051: (a5) if r9 < 0x2 goto pc+66
1052: ...
1053: (bf) r2 = r9 /* r2 needs to have upper and lower bounds */

This is normal behavior of greedy register allocator.
The slides 137+ explain why regalloc introduces such register copy:
http://llvm.org/devmtg/2018-04/slides/Yatsina-LLVM%20Greedy%20Register%20Allocator.pdf
There is no way to tell llvm 'not to do this'.
Hence the verifier has to recognize such patterns.

In order to track this information without backtracking allocate ID
for scalars in a similar way as it's done for find_good_pkt_pointers().

When the verifier encounters r9 = r6 assignment it will assign the same ID
to both registers. Later if either register range is narrowed via conditional
jump propagate the register state into the other register.

Clear register ID in adjust_reg_min_max_vals() for any alu instruction. The
register ID is ignored for scalars in regsafe() and doesn't affect state
pruning. mark_reg_unknown() clears the ID. It's used to process call, endian
and other instructions. Hence ID is explicitly cleared only in
adjust_reg_min_max_vals() and in 32-bit mov.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20201009011240.48506-2-alexei.starovoitov@gmail.com

2020-10-09 22:03:06 +02:00

Stanislav Fomichev

3b09d27cc9

selftests/bpf: Move test_align under test_progs

There is a much higher chance we can see the regressions if the
test is part of test_progs.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200515194904.229296-2-sdf@google.com

2020-05-16 01:18:14 +02:00

3 Commits (a5fc7aa901b6818c67cc7e5cef8201fbaab8fa1b)