From 550bec4fdef888873e595b63fd1af9cbc749b114 Mon Sep 17 00:00:00 2001
From: Kyle Evans <kevans@FreeBSD.org>
Date: Wed, 19 Feb 2020 14:32:55 +0000
Subject: [PATCH] kdump: decode SHM_ANON as first arg to legacy shm_open(2)

The first argument to shm_open(2) as well as shm_open2(2) may be a path or
SHM_ANON. Decode SHM_ANON, at least- paths will show up as namei results in
kdump output, which may be sufficient; in those cases, we'll have printed an
address.

Future commits will add support for shm_open2() to libsysdecode/truss/kdump.

Reported by:	kaktus
MFC after:	3 days
---
 usr.bin/kdump/kdump.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/usr.bin/kdump/kdump.c b/usr.bin/kdump/kdump.c
index 3319d2f06607..3c7e126bb33d 100644
--- a/usr.bin/kdump/kdump.c
+++ b/usr.bin/kdump/kdump.c
@@ -55,6 +55,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/uio.h>
 #include <sys/event.h>
 #include <sys/ktrace.h>
+#include <sys/mman.h>
 #include <sys/ioctl.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
@@ -1248,7 +1249,12 @@ ktrsyscall(struct ktr_syscall *ktr, u_int sv_flags)
 				break;
 #ifdef SYS_freebsd12_shm_open
 			case SYS_freebsd12_shm_open:
-				print_number(ip, narg, c);
+				if (ip[0] == (uintptr_t)SHM_ANON) {
+					printf("(SHM_ANON");
+					ip++;
+				} else {
+					print_number(ip, narg, c);
+				}
 				putchar(',');
 				print_mask_arg(sysdecode_open_flags, ip[0]);
 				putchar(',');