[PATCH RFC 8/9] scripts/gdb: reject trie-backed stack depot handles

[Caleb Kan <calebkan1106@gmail.com>]

From: Caleb Kan <ckan@cloudflare.com>

The lx-stack_depot_lookup command can materialize stacks only from
contiguous hash-backed records. Trie-backed handles instead encode a dense
stack ID in pool_index_plus_1 and offset, so treating them as hash handles
misreports a valid handle as an out-of-bounds pool index.

Reject pool_index_plus_1 values above stack_max_pools before the hash pool
lookup and report that trie-backed handles are unsupported. Supporting them
would require side-table and parent-link traversal in the helper, which is
left for future work.

Signed-off-by: Caleb Kan <ckan@cloudflare.com>
---
 scripts/gdb/linux/stackdepot.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/gdb/linux/stackdepot.py b/scripts/gdb/linux/stackdepot.py
index 37313a5a51a0..82aeb9f532c3 100644
--- a/scripts/gdb/linux/stackdepot.py
+++ b/scripts/gdb/linux/stackdepot.py
@@ -37,6 +37,10 @@ def stack_depot_fetch(handle):
     if handle == 0:
         raise gdb.GdbError("handle is 0\n")
 
+    stack_max_pools = gdb.parse_and_eval('stack_max_pools')
+    if parts['pool_index_plus_1'] > stack_max_pools:
+        raise gdb.GdbError("trie-backed stack depot handles are not supported\n")
+
     pool_index = parts['pool_index_plus_1'] - 1
     if pool_index >= pools_num:
         gdb.write("pool index %d out of bounds (%d) for stack id 0x%08x\n" % (parts['pool_index'], pools_num, handle))

-- 
Git-155)