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authorAndrii Nakryiko <andrii@kernel.org>2023-11-10 03:26:38 +0300
committerAlexei Starovoitov <ast@kernel.org>2023-11-10 07:11:20 +0300
commit62ccdb11d3c63dc697dea1fd92b3496fe43dcc1e (patch)
treeef2e9a422ae611e616fd521fc59a6b3b1cb97db3 /tools
parent4bb7ea946a370707315ab774432963ce47291946 (diff)
downloadlinux-62ccdb11d3c63dc697dea1fd92b3496fe43dcc1e.tar.xz
selftests/bpf: add edge case backtracking logic test
Add a dedicated selftests to try to set up conditions to have a state with same first and last instruction index, but it actually is a loop 3->4->1->2->3. This confuses mark_chain_precision() if verifier doesn't take into account jump history. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231110002638.4168352-4-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'tools')
-rw-r--r--tools/testing/selftests/bpf/progs/verifier_precision.c40
1 files changed, 40 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/verifier_precision.c b/tools/testing/selftests/bpf/progs/verifier_precision.c
index 193c0f8272d0..6b564d4c0986 100644
--- a/tools/testing/selftests/bpf/progs/verifier_precision.c
+++ b/tools/testing/selftests/bpf/progs/verifier_precision.c
@@ -91,3 +91,43 @@ __naked int bpf_end_bswap(void)
}
#endif /* v4 instruction */
+
+SEC("?raw_tp")
+__success __log_level(2)
+/*
+ * Without the bug fix there will be no history between "last_idx 3 first_idx 3"
+ * and "parent state regs=" lines. "R0_w=6" parts are here to help anchor
+ * expected log messages to the one specific mark_chain_precision operation.
+ *
+ * This is quite fragile: if verifier checkpointing heuristic changes, this
+ * might need adjusting.
+ */
+__msg("2: (07) r0 += 1 ; R0_w=6")
+__msg("3: (35) if r0 >= 0xa goto pc+1")
+__msg("mark_precise: frame0: last_idx 3 first_idx 3 subseq_idx -1")
+__msg("mark_precise: frame0: regs=r0 stack= before 2: (07) r0 += 1")
+__msg("mark_precise: frame0: regs=r0 stack= before 1: (07) r0 += 1")
+__msg("mark_precise: frame0: regs=r0 stack= before 4: (05) goto pc-4")
+__msg("mark_precise: frame0: regs=r0 stack= before 3: (35) if r0 >= 0xa goto pc+1")
+__msg("mark_precise: frame0: parent state regs= stack=: R0_rw=P4")
+__msg("3: R0_w=6")
+__naked int state_loop_first_last_equal(void)
+{
+ asm volatile (
+ "r0 = 0;"
+ "l0_%=:"
+ "r0 += 1;"
+ "r0 += 1;"
+ /* every few iterations we'll have a checkpoint here with
+ * first_idx == last_idx, potentially confusing precision
+ * backtracking logic
+ */
+ "if r0 >= 10 goto l1_%=;" /* checkpoint + mark_precise */
+ "goto l0_%=;"
+ "l1_%=:"
+ "exit;"
+ ::: __clobber_common
+ );
+}
+
+char _license[] SEC("license") = "GPL";