drgn.helpers.linux.printk: handle log_buf name conflict between v3.18…

… and v4.15 In a few kernel versions with structured printk, printk and the BPF verifier both had static global variables named log_buf. get_printk_records() doesn't handle this. We never hit this before with the old DWARF index, but the rework exposed this for some reason. Pass the filename so we always get the right one. Fixes: ba51e88 ("helpers: add get_printk_records()") Signed-off-by: Omar Sandoval <[email protected]>
osandov · Aug 17, 2023 · 7ac5007 · 7ac5007
1 parent bc85145
commit 7ac5007
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/drgn/helpers/linux/printk.py b/drgn/helpers/linux/printk.py
@@ -170,7 +170,11 @@ def _get_printk_records_structured(prog: Program) -> List[PrintkRecord]:
     LOG_CONT = prog["LOG_CONT"].value_()
 
     result = []
-    log_buf = prog["log_buf"].read_()
+    # Between Linux kernel commits cbd357008604 ("bpf: verifier (add ability to
+    # receive verification log)") (in v3.18) and e7bf8249e8f1 ("bpf:
+    # encapsulate verifier log state into a structure") (in v4.15),
+    # kernel/bpf/verifier.c also contains a variable named log_buf.
+    log_buf = prog.object("log_buf", filename="printk.c").read_()
     current_idx = prog["log_first_idx"].read_()
     next_idx = prog["log_next_idx"].read_()
     seq = prog["log_first_seq"].value_()