scripts/gdb: fix lx-version for gdb 7.3-

PATCH Superseded Du Changbin 3 participants 4 messages Oct 17, 2018 GDB kernel debugging helper scripts

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Du Changbin

author

2018-10-17 02:36 UTC #0 lore raw

PATCH 1/1 scripts/gdb: fix lx-version for gdb 7.3-

For gdb version less than 7.3, lx-version only 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

gdb 7.4 seems to be no such issue.

Signed-off-by Du Changbin <[email protected]>

---
 scripts/gdb/linux/proc.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

scripts/gdb/linux/proc.py +1 -1

index 086d27223c0c..0aebd7565b03 100644
@@ -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()

Signature · 1 line

2.17.1

Jan Kiszka

maintainer

2018-10-17 06:56 UTC #1 lore raw

Quoted 1 line · Du Changbin

For gdb version less than 7.3, lx-version only one character.

                                          ^^^ prints?

Quoted 20 lines

(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
gdb 7.4 seems to be no such issue.
Signed-off-by Du Changbin <[email protected]>
---
  scripts/gdb/linux/proc.py | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)
scripts/gdb/linux/proc.py +0 -0
index 086d27223c0c..0aebd7565b03 100644

scripts/gdb/linux/proc.py class LxVersion(gdb.Command): · line 47

Quoted 8 lines

scripts/gdb/linux/proc.py +1 -1

@@ -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()

Looks good to me otherwise.

Jan

Signature · 2 lines

Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

Changbin Du

author

2018-10-17 13:40 UTC #2 lore raw

Quoted 5 lines · Jan Kiszka

Quoted 1 line · Du Changbin
For gdb version less than 7.3, lx-version only one character.
                                          ^^^ prints?

I will update it, thanks!

Quoted 28 lines

Quoted 19 lines
(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
gdb 7.4 seems to be no such issue.
Signed-off-by Du Changbin <[email protected]>
---
  scripts/gdb/linux/proc.py | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)
scripts/gdb/linux/proc.py +0 -0
index 086d27223c0c..0aebd7565b03 100644
scripts/gdb/linux/proc.py class LxVersion(gdb.Command): · line 45
Quoted 6 lines
scripts/gdb/linux/proc.py +1 -1
@@ -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()
 
Looks good to me otherwise.

Quoted 5 lines

Jan
--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE Corporate Competence Center Embedded Linux

--
Thanks,
Du Changbin

Kieran Bingham

Reviewed-by on v1 1/1

2018-10-17 12:31 UTC #3 lore raw

In reply to Du Changbin

Hi Du,

Quoted 20 lines · Du Changbin

For gdb version less than 7.3, lx-version only 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
gdb 7.4 seems to be no such issue.
Signed-off-by Du Changbin <[email protected]>
---
 scripts/gdb/linux/proc.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
scripts/gdb/linux/proc.py +0 -0
index 086d27223c0c..0aebd7565b03 100644

scripts/gdb/linux/proc.py class LxVersion(gdb.Command): · line 44

Quoted 5 lines

scripts/gdb/linux/proc.py +1 -1

@@ -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())

Interesting - this is an issue I reported to the GDB team after I'd tried to dig into the fault.

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

the parse_and_eval finds a string length of 0, but then later in the GBD parsing it gets incremented to 1, hence the single char. I guess it's some failure in GDB determining the type of the pointer.

However, from reading the bugzilla entry and from what I recall - it only occurred if you had done a backtrace before calling lx-version.

Did you discover that it would always return only the single character in your testing ? Even if it was the first command executed?

My worry is - that if this fixes lx-version - do we also need to manually cast lx-cmdline as well ? (I never saw the issue occur on that cmd).

I think considering the age of the bugzilla at GDB, and the lack of any GDB level fix or understanding - we should certainly apply this fix here
- and probably include it in the stable trees too.

With the title fix as highlighted by Jan,

Reviewed-by Kieran Bingham <[email protected]>

Would you be able to test the issue with the lx-cmdline command as well please? And if it is suffering the same issue - perhaps you could either submit a second patch to update that entry - or respin this one to include both?

Quoted 4 lines

scripts/gdb/linux/proc.py +0 -0
 LxVersion()
 
 

Signature · 3 lines

Regards
--
Kieran