[PATCH AUTOSEL 4.20 303/304] scripts/gdb: fix lx-version string output

[Sasha Levin]

From: Du Changbin <changbin.du@xxxxxxxxx>

[ Upstream commit b058809bfc8faeb7b7cae047666e23375a060059 ]

A bug is present in GDB which causes early string termination when
parsing variables.  This has been reported [0], but we should ensure
that we can support at least basic printing of the core kernel strings.

For current gdb version (has been tested with 7.3 and 8.1), 'lx-version'
only prints one character.

  (gdb) lx-version
  L(gdb)

This can be fixed by casting 'linux_banner' as (char *).

  (gdb) lx-version
  Linux version 4.19.0-rc1+ (changbin@acer) (gcc version 7.3.0 (Ubuntu 7.3.0-16ubuntu3)) #21 SMP Sat Sep 1 21:43:30 CST 2018

[0] https://sourceware.org/bugzilla/show_bug.cgi?id=20077

[kbingham@xxxxxxxxxx: add detail to commit message]
Link: http://lkml.kernel.org/r/20181111162035.8356-1-kieran.bingham@xxxxxxxxxxxxxxxx
Fixes: 2d061d999424 ("scripts/gdb: add version command")
Signed-off-by: Du Changbin <changbin.du@xxxxxxxxx>
Signed-off-by: Kieran Bingham <kbingham@xxxxxxxxxx>
Acked-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
Cc: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
Cc: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
Cc: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 scripts/gdb/linux/proc.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/gdb/linux/proc.py b/scripts/gdb/linux/proc.py
index 086d27223c0c..0aebd7565b03 100644
--- a/scripts/gdb/linux/proc.py
+++ b/scripts/gdb/linux/proc.py
@@ -41,7 +41,7 @@ class LxVersion(gdb.Command):
 
     def invoke(self, arg, from_tty):
         # linux_banner should contain a newline
-        gdb.write(gdb.parse_and_eval("linux_banner").string())
+        gdb.write(gdb.parse_and_eval("(char *)linux_banner").string())
 
 LxVersion()
 
-- 
2.19.1