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Re:
See 6.3 in https://www.kernel.org/doc/Documentation/kbuild/modules.txt
for intricate details. The bottom line is that STAP builds modules in
a specific environment which can not be easily (or at least I do not
know how to) controlled.
On Sun, Jul 30, 2017 at 10:17 AM, Arkady <arkady.miasnikov@gmail.com> wrote:
> This link can be relevant
> https://stackoverflow.com/questions/33718358/insmod-fails-with-unknown-symbol-in-module-for-a-symbol-defined-in-another-mod
>
> On Sun, Jul 30, 2017 at 10:09 AM, Arkady <arkady.miasnikov@gmail.com> wrote:
>> Daniel,
>>
>> STAP attempts to compile the kernel module against the kernel source
>> tree installed in the system. One way to resolve the issue is to
>> update the kernel source tree installed in the system. Without
>> updating the kernel sources the compilation will fail.
>>
>> On Sun, Jul 30, 2017 at 9:56 AM, Daniel Doron <danielmeirdoron@gmail.com> wrote:
>>> Hi,
>>>
>>> How is systemtap's kernel module different from other modules?
>>> Given module A which exports a function and module B using that exported
>>> function and A is insmodded before B, I have not seen any problem. Why is
>>> Systemtap's KO different? Is it not the kernel's job to resolve the exported
>>> symbol?
>>>
>>>
>>> Daniel.
>>>
>>> On Thu, 27 Jul 2017 at 19:29 Arkady <arkady.miasnikov@gmail.com> wrote:
>>>>
>>>> P.S.1 There is yet another way - very cool way - to to add a symbol to
>>>> the stap script - via /sys/kernel/debug/systemtap/<module name>/.cmd
>>>> (CTL_CHANNEL_NAME below)
>>>>
>>>> This is a Python sample
>>>>
>>>> def write_relocate_string(f, s, size):
>>>> f.write(s)
>>>> padding = size - len(s)
>>>> for _ in range(padding):
>>>> f.write('\x00')
>>>>
>>>> def write_relocate(module_name, symbol_name, address):
>>>> STP_MODULE_NAME_LEN = 128
>>>> STP_SYMBOL_NAME_LEN = 128
>>>>
>>>> with open(CTL_CHANNEL_NAME, "wb") as f:
>>>> # STAP_RELOCATE (9)
>>>> f.write(struct.pack('<I', 9))
>>>> write_relocate_string(f, module_name, STP_MODULE_NAME_LEN)
>>>> write_relocate_string(f, symbol_name, STP_SYMBOL_NAME_LEN)
>>>> f.write(struct.pack('<Q', address))
>>>>
>>>>
>>>>
>>>> On Thu, Jul 27, 2017 at 7:20 PM, Arkady <arkady.miasnikov@gmail.com>
>>>> wrote:
>>>> > P.S. Another idea is to use kernel IPC instead of function calls.
>>>> > Files, named pipes, sockets, memory mapped files - just about anything
>>>> > can do the trick.
>>>> >
>>>> > On Thu, Jul 27, 2017 at 7:03 PM, Arkady <arkady.miasnikov@gmail.com>
>>>> > wrote:
>>>> >> Eyal,
>>>> >>
>>>> >> Utility stap employs the kernel debug information installed in the
>>>> >> system. When you load a module command insmod does not update the
>>>> >> kernel debug info. There are simple two ways to resolve the issue
>>>> >> * Load the module, get the address of the function foo using
>>>> >> /proc/kallsyms, provide the address of the foo as an argument to the
>>>> >> STAP script.
>>>> >> * Link the module statically with the kernel and update the
>>>> >> kernel-debuginfo
>>>> >>
>>>> >> Arkady
>>>> >>
>>>> >> On Thu, Jul 27, 2017 at 5:47 PM, Eyal Yehuda via systemtap
>>>> >> <systemtap@sourceware.org> wrote:
>>>> >>>
>>>> >>>
>>>> >>> 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
>>>>
>>>