[Crash-utility] [PATCH v2 1/1] Support member offset uts_namespace.name

[Alexander Egorenkov]

The offset of the field 'init_uts_ns.name' has changed
since commit 9a56493f6942 ("uts: Use generic ns_common::count").

Link: https://lore.kernel.org/r/159644978167.604812.1773586504374412107.stgit@localhost.localdomain

Read the offset from VMCOREINFO if present. This requires a linux version
which exports the requisite offset in VMCOREINFO.

Signed-off-by: Alexander Egorenkov <egorenar at linux.ibm.com>
---

v1 -> v2:
 * Use offset from VMCOREINFO
 * Initialize corresponding entry in offset_table

 defs.h    |  1 +
 kernel.c  | 15 ++++++++++-----
 symbols.c |  3 +++
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/defs.h b/defs.h
index c899fe2..9a8030a 100644
--- a/defs.h
+++ b/defs.h
@@ -2104,6 +2104,7 @@ struct offset_table {                    /* stash of commonly-used offsets */
 	long inode_i_sb_list;
 	long irq_common_data_affinity;
 	long irq_desc_irq_common_data;
+	long uts_namespace_name;
 };
 
 struct size_table {         /* stash of commonly-used sizes */
diff --git a/kernel.c b/kernel.c
index 5ae8cf1..9871637 100644
--- a/kernel.c
+++ b/kernel.c
@@ -230,16 +230,21 @@ kernel_init()
 		fprintf(fp, "%s\n\n", ctime_tz(&kt->date.tv_sec));
 		clean_exit(0);
 	}
-	
+
+	MEMBER_OFFSET_INIT(uts_namespace_name, "uts_namespace", "name");
 	if (symbol_exists("system_utsname"))
         	readmem(symbol_value("system_utsname"), KVADDR, &kt->utsname,
                 	sizeof(struct new_utsname), "system_utsname", 
 			RETURN_ON_ERROR);
-	else if (symbol_exists("init_uts_ns"))
-		readmem(symbol_value("init_uts_ns") + sizeof(int),
-			KVADDR,  &kt->utsname, sizeof(struct new_utsname), 
+	else if (symbol_exists("init_uts_ns")) {
+		long offset = sizeof(int);
+		if (VALID_MEMBER(uts_namespace_name))
+			offset = OFFSET(uts_namespace_name);
+
+		readmem(symbol_value("init_uts_ns") + offset,
+			KVADDR,  &kt->utsname, sizeof(struct new_utsname),
 			"init_uts_ns", RETURN_ON_ERROR);
-	else
+	} else
 		error(INFO, "cannot access utsname information\n\n");
 
 	if (CRASHDEBUG(1)) {
diff --git a/symbols.c b/symbols.c
index d22fb1d..3dd5fa1 100644
--- a/symbols.c
+++ b/symbols.c
@@ -10585,6 +10585,9 @@ dump_offset_table(char *spec, ulong makestruct)
 	fprintf(fp, "                 xa_node_shift: %ld\n",
 		OFFSET(xa_node_shift));
 
+	fprintf(fp, "            uts_namespace_name: %ld\n",
+		OFFSET(uts_namespace_name));
+
 	fprintf(fp, "\n                    size_table:\n");
 	fprintf(fp, "                          page: %ld\n", SIZE(page));
 	fprintf(fp, "                    page_flags: %ld\n", SIZE(page_flags));
-- 
2.26.2