[no subject]

["Eyal Yehuda via systemtap" <systemtap at sourceware dot org>]

hello

The
 issue I am facing is of undefined symbols in system tap kernel module 
when trying to link to another kernel module with exported symbol

please note environment setup:
os:  debian 9 stretch 64bit
kernel version:  4.9.0-3-amd64
 

          I created the following simple systemtap script using guru mode   

          system tap script:      temp.stp       

 
         %{
                 extern int foo(void);
         %}

          function call_foo:long() %{/* pure */
                  STAP_RETVALUE = foo();
         %}

          probe syscall.open {
                 printf("foo() : %d\n",  call_foo())
          }
 


        
 In addition to that I created the following simple kernel module with 
an exported symbol function to be used from inside system tap 
script           
        
         kernel module:       xxx.c 

         #include <linux/kernel.h>
         #include <linux/module.h>
         #include <linux/printk.h>

         static int foo(void){
                 pr_info("foo()\n"); return 0;
         }
         EXPORT_SYMBOL(foo);

         static int __init xxx_init(void){
                pr_info("xxx_init()\n");  
           return 0;
         }

         static void __exit xxx_exit(void){
                pr_info("xxx_exit() \n");
         }

         module_init(xxx_init);
         module_exit(xxx_exit);
         MODULE_LICENSE("GPL");

 
         After compiling the kernel module and insmoding it, I run the command to compile systemtap script as follow:  
         stap -gk -v temp.stp  

         the compilation command result with the following error:
           
        
 Pass 1: parsed user script and 465 library scripts using 
113912virt/46752res/6476shr/40564data kb, in 110usr/20sys/124real ms.
        
 Pass 2: analyzed script: 2 probes, 2 functions, 99 embeds, 0 globals 
using 165912virt/100212res/7716shr/92564data kb, in 680usr/50sys/731real
 ms.
        
 Pass 3: translated to C into "/tmp/stapzKUZ11/stap_1837_src.c" using 
165912virt/100404res/7908shr/92564data kb, in 10usr/10sys/9real ms.
         WARNING: "foo" [/tmp/stapzKUZ11/stap_1837.ko] undefined!
         Pass 4: compiled C into "stap_1837.ko" in 1410usr/120sys/1963real ms.
         Pass 5: starting run.
         ERROR: Couldn't insert module '/tmp/stapzKUZ11/stap_1837.ko': Invalid parameters
         WARNING: /usr/bin/staprun exited with status: 1
         Pass 5: run completed in 0usr/0sys/16real ms.
         Pass 5: run failed.  [man error::pass5]
         Tip: /usr/share/doc/systemtap/README.Debian should help you get started.
         Keeping temporary directory "/tmp/stapzKUZ11"
 

         in dmesg I can see the following lines
        
         Jul 27 03:56:14 debian9 kernel: [ 3938.166906] stap_2230: no symbol version for foo
         Jul 27 03:56:14 debian9 kernel: [ 3938.166908] stap_2230: Unknown symbol foo (err -22)
 

         I also checked /proc/kallsyms 
        
 
         cat /proc/kallsyms | grep xxx
         ffffffffc0584000 T foo    [xxx]
         ffffffffc0584014 t xxx_exit    [xxx]
         ffffffffc0585030 r __ksymtab_foo    [xxx]
         ffffffffc058506e r __kstrtab_foo    [xxx]
         ffffffffc0585040 r __kcrctab_foo    [xxx]
         ffffffffc0586000 d __this_module    [xxx]
         ffffffffc0584014 t cleanup_module    [xxx]

 
Please advice
1.
 what should i do in addition to solve this issue as I must create an 
interaction between systemtap script and another kernel module
2.
 In case this is not feasible can u please offer another alternative to 
make systemtap script use another kernel module services ?

Thanks eyal yehuda