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| author | Alexei Starovoitov <ast@kernel.org> | 2024-06-12 18:38:13 -0700 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2024-06-14 21:52:39 +0200 |
| commit | 98d7ca374ba4b39e7535613d40e159f09ca14da2 (patch) | |
| tree | cc45a92aa7645787141a5f250bc085c9f815fbc3 /tools | |
| parent | 124e8c2b1b5d08a10d3a44ed082eaaf98a78c91f (diff) | |
| download | linux-next-98d7ca374ba4b39e7535613d40e159f09ca14da2.tar.gz linux-next-98d7ca374ba4b39e7535613d40e159f09ca14da2.zip | |
bpf: Track delta between "linked" registers.
Compilers can generate the code
r1 = r2
r1 += 0x1
if r2 < 1000 goto ...
use knowledge of r2 range in subsequent r1 operations
So remember constant delta between r2 and r1 and update r1 after 'if' condition.
Unfortunately LLVM still uses this pattern for loops with 'can_loop' construct:
for (i = 0; i < 1000 && can_loop; i++)
The "undo" pass was introduced in LLVM
https://reviews.llvm.org/D121937
to prevent this optimization, but it cannot cover all cases.
Instead of fighting middle end optimizer in BPF backend teach the verifier
about this pattern.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240613013815.953-3-alexei.starovoitov@gmail.com
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/testing/selftests/bpf/verifier/precise.c | 22 |
1 files changed, 11 insertions, 11 deletions
diff --git a/tools/testing/selftests/bpf/verifier/precise.c b/tools/testing/selftests/bpf/verifier/precise.c index 0a9293a57211..90643ccc221d 100644 --- a/tools/testing/selftests/bpf/verifier/precise.c +++ b/tools/testing/selftests/bpf/verifier/precise.c @@ -39,12 +39,12 @@ .result = VERBOSE_ACCEPT, .errstr = "mark_precise: frame0: last_idx 26 first_idx 20\ - mark_precise: frame0: regs=r2 stack= before 25\ - mark_precise: frame0: regs=r2 stack= before 24\ - mark_precise: frame0: regs=r2 stack= before 23\ - mark_precise: frame0: regs=r2 stack= before 22\ - mark_precise: frame0: regs=r2 stack= before 20\ - mark_precise: frame0: parent state regs=r2 stack=:\ + mark_precise: frame0: regs=r2,r9 stack= before 25\ + mark_precise: frame0: regs=r2,r9 stack= before 24\ + mark_precise: frame0: regs=r2,r9 stack= before 23\ + mark_precise: frame0: regs=r2,r9 stack= before 22\ + mark_precise: frame0: regs=r2,r9 stack= before 20\ + mark_precise: frame0: parent state regs=r2,r9 stack=:\ mark_precise: frame0: last_idx 19 first_idx 10\ mark_precise: frame0: regs=r2,r9 stack= before 19\ mark_precise: frame0: regs=r9 stack= before 18\ @@ -100,11 +100,11 @@ .errstr = "26: (85) call bpf_probe_read_kernel#113\ mark_precise: frame0: last_idx 26 first_idx 22\ - mark_precise: frame0: regs=r2 stack= before 25\ - mark_precise: frame0: regs=r2 stack= before 24\ - mark_precise: frame0: regs=r2 stack= before 23\ - mark_precise: frame0: regs=r2 stack= before 22\ - mark_precise: frame0: parent state regs=r2 stack=:\ + mark_precise: frame0: regs=r2,r9 stack= before 25\ + mark_precise: frame0: regs=r2,r9 stack= before 24\ + mark_precise: frame0: regs=r2,r9 stack= before 23\ + mark_precise: frame0: regs=r2,r9 stack= before 22\ + mark_precise: frame0: parent state regs=r2,r9 stack=:\ mark_precise: frame0: last_idx 20 first_idx 20\ mark_precise: frame0: regs=r2,r9 stack= before 20\ mark_precise: frame0: parent state regs=r2,r9 stack=:\ |