9:39 p.m.
Hi Dave,
On 06/13/2014 12:55 PM, Dave Anderson wrote:
----- Original Message -----
>
>
> ----- Original Message -----
>> When the crash command line includes two filenames where one is a
>> compressed kernel and the other is a debuginfo file and they appear in
>> that order then if the uncompressed temporary version of the kernel is
>> actually larger than the debuginfo then crash will end with an error but
>> will also unlink the debuginfo file and will not clean up the (intended
>> temporary) uncompressed copy of the kernel.
>
> Hi Dave,
>
> It's taken me awhile to wrap my head around this, but my first question is:
> how is it possible that the uncompressed stripped kernel can possibly be
> larger than the debuginfo file?
>
> I only have old RHEL3 kernels as examples, but the .debug versions
> of the kernel are 5 to 6 times larger than the stripped kernel.
>
>> This patch at least fixes the unintended unlink and leaving the
>> temporary present. It doesn't fix the failure to start but that's
>> because the wrong files are assumed the debuginfo and kernel. The size
>> case that led to this discovery is probably rare.
>
> Is the unintended unlink() done in the first display_sys_stats() or
> in clean_exit()?
>
> And then with your fix applied, why does the crash session still fail?
>
> Dave
Hi Dave,
Although I'm still interested in answers to the questions above, this
patch also fixes a different scenario.
In testing the 8 possible combinations using RHEL3 vmlinux/vmlinux.gz
and vmlinux.debug/vmlinux.debug.gz files, I found that I could reproduce
the problem with this particular combination/order:
$ crash vmlinux.debug.gz vmlinux ...
Similar to your setup, the pc->namelist_orig field continues to
be non-NULL, and therefore pc->namelist (vmlinux) gets removed in
clean_exit(), and since pc->namelist_debug_orig doesn't get set,
the uncompressed temporary debug file remains!
Yes, vmlinux.gz passes is_compressed_kernel() and there is a tmpname
(vmlinux.debug_XXXXXX with unique name replacement of XXXXXX).
select_namelist() gets called with tmpname (as the argument new) and all
the namelist values in pc are NULL. select_namelist() uses new to set
pc->namelist (to vmlinux.debug_XXXXXX). On return to main(),
pc->namelist_orig gets set to argv[optind] (vmlinux.debug.gz).
argv[optind] = vmlinux.debug.gz
// State before select_namelist()
pc->namelist is NULL
pc->namelist_orig is NULL
pc->namelist_debug is NULL
pc->namelist_debug_orig is NULL
select_namelist(vmlinux.debug_XXXXXX)
// State shortly after select_namelist()
pc->namelist is vmlinux.debug_XXXXXX
pc->namelist_orig is vmlinux.debug.gz
pc->namelist_debug is NULL
pc->namelist_debug_orig is NULL
The next argument, vmlinux, passes is_kernel() and select_namelist()
gets called with argv[optind] (as the argument new). Since there is a
namelist value already select_namelist() gets the struct stat for each
file (vmlinux.debug_XXXXXX and vmlinux, the first is a larger file).
select_namelist() copies pc->namelist (vmlinux.debug_XXXXXX) to
pc->namelist_debug and sets pc->namelist from new (vmlinux) leaving
pc->namelist_orig set to vmlinux.debug.gz and pc->namelist_debug_orig as
NULL.
argv[optind] = vmlinux
// State before select_namelist()
pc->namelist is vmlinux.debug_XXXXXX
pc->namelist_orig is vmlinux.debug.gz
pc->namelist_debug is NULL
pc->namelist_debug_orig is NULL
select_namelist(vmlinux)
// State shortly after select_namelist()
pc->namelist is vmlinux
pc->namelist_orig is vmlinux.debug.gz
pc->namelist_debug is vmlinux.debug_XXXXXX
pc->namelist_debug_orig is NULL
That leaves namelist_debug with no indication it is an uncompressed,
temporary file (the equivalent _orig member of pc is NULL) and indicates
vmlinux is an uncompressed temporary file (the equivalent _orig member
of pc is non-NULL) when clean_exit() is used so there is an unintended
unlink of vmlinux and an uncleaned vmlinux.debug_XXXXXX temporary.
Nice fix!
Thanks, I'm glad to help.
--
David.
>
>
>> The cause is that evidence of a temporary file to unlink is that there
>> is a value in pc->namelist and pc->namelist_orig (or pc->namelist_debug
>> and pc->namelist_orig_debug) but when the file size test in
>> select_namelist() results in the pc->namelist copy to pc->namelist_debug
>> the _orig is not copied as well so the implied file to unlink is the one
>> set in pc->namelist (the debuginfo filename now).
>>
>> The patch causes a populated namelist_orig value to be swapped with
>> namelist_debug_orig if the namelist value is copied to namelist_debug.
>>
>> Signed-off-by: David Mair <dmair(a)suse.com>
>> ---
>> symbols.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/symbols.c b/symbols.c
>> index 4c6fbf4..e1ed719 100644
>> --- a/symbols.c
>> +++ b/symbols.c
>> @@ -3520,6 +3520,7 @@ int
>> select_namelist(char *new)
>> {
>> struct stat stat1, stat2;
>> + char *namecp;
>>
>> if (pc->server_namelist) {
>> pc->namelist_debug = new;
>> @@ -3533,6 +3534,12 @@ select_namelist(char *new)
>>
>> if (stat1.st_size > stat2.st_size) {
>> pc->namelist_debug = pc->namelist;
>> + if (pc->namelist_orig)
>> + {
>> + namecp = pc->namelist_debug_orig;
>> + pc->namelist_debug_orig = pc->namelist_orig;
>> + pc->namelist_orig = namecp;
>> + }
>> pc->namelist = new;
>> } else if (stat2.st_size > stat1.st_size)
>> pc->namelist_debug = new;
>>
>> --
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>>
>
> --
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