Hi Atsushi,
On 2012-12-20 14:15, Atsushi Kumagai wrote:
> Hello Aravinda,
>
> Thank you for updating.
> I have two comments in this mail.
>
>
> On Fri, 14 Dec 2012 14:56:04 +0530
> Aravinda Prasad <aravinda at linux.vnet.ibm.com> wrote:
>
>> This patch contains routines which initialize eppic and register call
>> back function which will be called whenever a new eppic macro is loaded
>> using eppic_load() API. The registered call back function executes the
>> eppic macro as soon as it is loaded.
>>
>> Signed-off-by: Aravinda Prasad <aravinda at linux.vnet.ibm.com>
>> ---
>> Makefile | 5 +++
>> extension_eppic.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>> extension_eppic.h | 23 +++++++++++++++
>> 3 files changed, 111 insertions(+), 1 deletions(-)
>> create mode 100644 extension_eppic.c
>> create mode 100644 extension_eppic.h
>>
>> diff --git a/Makefile b/Makefile
>> index e6c4e5d..f123a5f 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -69,7 +69,7 @@ $(OBJ_ARCH): $(SRC_ARCH)
>> $(CC) $(CFLAGS_ARCH) -c -o ./$@ ./$(@:.o=.c)
>>
>> makedumpfile: $(SRC) $(OBJ_PART) $(OBJ_ARCH)
>> - $(CC) $(CFLAGS) $(LDFLAGS) $(OBJ_PART) $(OBJ_ARCH) -o $@ $< $(LIBS)
>> + $(CC) $(CFLAGS) $(LDFLAGS) $(OBJ_PART) $(OBJ_ARCH) -rdynamic -o $@ $< $(LIBS)
>> echo .TH MAKEDUMPFILE 8 \"$(DATE)\" \"makedumpfile v$(VERSION)\" \"Linux System Administrator\'s Manual\" > temp.8
>> grep -v "^.TH MAKEDUMPFILE 8" makedumpfile.8 >> temp.8
>> mv temp.8 makedumpfile.8
>> @@ -79,6 +79,9 @@ makedumpfile: $(SRC) $(OBJ_PART) $(OBJ_ARCH)
>> mv temp.5 makedumpfile.conf.5
>> gzip -c ./makedumpfile.conf.5 > ./makedumpfile.conf.5.gz
>>
>> +eppic_makedumpfile.so: extension_eppic.c
>> + $(CC) $(CFLAGS) -nostartfiles -shared -rdynamic -o $@ extension_eppic.c -fPIC -leppic
>> +
>
> First, I prepared eppic_makedumpfile.so with the code above, but I failed
> with the message below:
>
> $ makedumpfile -cd31 -x vmlinux --eppic eppic_macro/mod.c vmcore dumpfile.cd31
> process_eppic_file: dlopen failed: /usr/lib64/eppic_makedumpfile.so: undefined symbol: setupterm
>
> makedumpfile Failed.
> $
>
> so I think '-lncurses' should be specified as gcc option, or did I mistake ?
-ltinfo was missing in the gcc option.
>
>
> [...]
>> +/* Initialize eppic */
>> +int
>> +_init()
>> +{
>> + if (eppic_open() >= 0) {
>> +
>> + /* Register call back functions */
>> + eppic_apiset(NULL, 3, sizeof(long), 0);
>> +
>> + /* set the new function callback */
>> + eppic_setcallback(reg_callback);
>> +
>> + return 0;
>> + }
>> + return 1;
>> +}
>
> Second, your code introduce _init() as constructor for dlopen().
> I'm not sure about dlopen(), but I found the description which recommend
> not to use _init() in man page:
>
> The obsolete symbols _init() and _fini()
> The linker recognizes special symbols _init and _fini. If a dynamic library exports a routine named _init(), then that code is executed
> after the loading, before dlopen() returns. If the dynamic library exports a routine named _fini(), then that routine is called just
> before the library is unloaded. In case you need to avoid linking against the system startup files, this can be done by using the gcc(1)
> -nostartfiles command-line option.
>
> Using these routines, or the gcc -nostartfiles or -nostdlib options, is not recommended. Their use may result in undesired behavior, since
> the constructor/destructor routines will not be executed (unless special measures are taken).
>
> Instead, libraries should export routines using the __attribute__((constructor)) and __attribute__((destructor)) function attributes. See
> the gcc info pages for information on these. Constructor routines are executed before dlopen() returns, and destructor routines are exe-
> cuted before dlclose() returns.
>
> So, is it OK to continue to use _init() ?
I am planning to change _init() to eppic_init() and then explicitly call
it after dlopen(), as using _init() is not recommended.
Apart from this I am facing some minor issues with dlopen(). With static
makedumpfile, dlopen is not able to resolve some symbols in dwarf_info.c
and is failing, while it is working when compiled with LINKTYPE=dynamic.
I am looking into it.
>
> BTW, would you send the patch to add the description of this feature
> to README, man page and help message ?
>
>
> Thanks
> Atsushi Kumagai
>
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>
--
Regards,
Aravinda
