linux-kernel - [stable 4.9.y 4/4] scripts/gdb: fix lx-version string output

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Message-Id: <20210107225229.1502459-5-f.fainelli@gmail.com>
Date:   Thu,  7 Jan 2021 14:52:29 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Du Changbin <changbin.du@...il.com>,
        Kieran Bingham <kbingham@...nel.org>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Kieran Bingham <kieran@...uared.org.uk>,
        Leonard Crestez <leonard.crestez@....com>,
        André Draszik <git@...red.net>
Subject: [stable 4.9.y 4/4] scripts/gdb: fix lx-version string output

From: Du Changbin <changbin.du@...il.com>

commit b058809bfc8faeb7b7cae047666e23375a060059 upstream

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@...r) (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@...nel.org: add detail to commit message]
Link: http://lkml.kernel.org/r/20181111162035.8356-1-kieran.bingham@ideasonboard.com
Fixes: 2d061d999424 ("scripts/gdb: add version command")
Signed-off-by: Du Changbin <changbin.du@...il.com>
Signed-off-by: Kieran Bingham <kbingham@...nel.org>
Acked-by: Jan Kiszka <jan.kiszka@...mens.com>
Cc: Jan Kiszka <jan.kiszka@...mens.com>
Cc: Jason Wessel <jason.wessel@...driver.com>
Cc: Daniel Thompson <daniel.thompson@...aro.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
---
 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 38b1f09d1cd9..822e3767bc05 100644
--- a/scripts/gdb/linux/proc.py
+++ b/scripts/gdb/linux/proc.py
@@ -40,7 +40,7 @@ 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()
 
-- 
2.25.1