From: Miod Vallat <miod@online.fr>
Subject: infinite loop in pcidump
To: tech@openbsd.org
Date: Sat, 29 Aug 2026 05:14:49 +0000

I have a PCIe device here, with the whole PCIe configuration space
read returning all bits set to one (i.e. 0xffffffff).

When running pcidump -v on this device, I get this:

	[...]
	0x0100: Enhanced Capability 0xffff: Unknown
	0x0ffc: Enhanced Capability 0xffff: Unknown
	0x0ffc: Enhanced Capability 0xffff: Unknown
	0x0ffc: Enhanced Capability 0xffff: Unknown
	0x0ffc: Enhanced Capability 0xffff: Unknown
	[ ad nauseam ]

The following diff tries to recognize this and break from the loop.

Index: pcidump.c
===================================================================
RCS file: /OpenBSD/src/usr.sbin/pcidump/pcidump.c,v
diff -u -p -r1.73 pcidump.c
--- pcidump.c	25 Dec 2025 10:59:26 -0000	1.73
+++ pcidump.c	29 Aug 2026 05:12:14 -0000
@@ -675,6 +675,9 @@ dump_pcie_enhanced_caplist(int bus, int 
 		if (pci_read(bus, dev, func, ptr, &reg) != 0)
 			return;
 
+		if (reg == 0xffffffffU)
+			return;
+
 		if (PCI_PCIE_ECAP_ID(reg) == 0xffff &&
 		    PCI_PCIE_ECAP_NEXT(reg) == PCI_PCIE_ECAP_LAST)
 			return;