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Re: dwarf info in modules.


upgrading elfutils to 0.115 solved the "no dwarf info found" but now I get an oops:

# general protection fault: 0000 [1] SMP

Entering kdb (current=0x0000010037d5c7f0, pid 10908) on processor 0 Oops: <NULL>
due to oops @ 0xffffffff801229da
r15 = 0x0000007fbffff310 r14 = 0x0000000000000246
r13 = 0x0000000000000000 r12 = 0xffffffffa01cdc20
rbp = 0x00000100497fbdc8 rbx = 0x0000000000000000
r11 = 0x0000000000000246 r10 = 0x0000007fbffff314
r9 = 0x8000000000000003 r8 = 0xffffffffa01cdc20
rax = 0x0000000000000000 rcx = 0x000000000000000f
rdx = 0x8000000000000000 rsi = 0x8000000000000003
rdi = 0xffffffffa000000f orig_rax = 0xffffffffffffffff
rip = 0xffffffff801229da cs = 0x0000000000000010
eflags = 0x0000000000010046 rsp = 0x00000100497fbdb0
ss = 0x00000100497fa000 &regs = 0x00000100497fbd18
[0]kdb> bt
Stack traceback for pid 10908
0x0000010037d5c7f0 10908 10856 1 0 R 0x0000010037d5cbf0 *stpd
RBP RIP Function (args)
0x100497fbdc8 0xffffffff801229da arch_copy_kprobe+0x16 (0xffffffffa01cdc20, 0x7fbffff314, 0x100497fbe84, 0x4, 0x100497fbf48)
0x100497fbe08 0xffffffff8015cbc0 register_kprobe+0x1e7 (0xffffffffa01cdc20, 0x7fbffff314, 0x7fbffff314, 0x100497fbe84)
0x100497fbe38 0xffffffffa01ca78e [stap_10856]probe_start+0x2e (0x100497fa000, 0x100497fa000)
0x100497fbe58 0xffffffffa01ca80a [stap_10856]_stp_handle_start+0xf (0x100497fbe84, 0x100497fbe88, 0x50ce40, 0x500000018, 0x100497fbec8)
0x100497fbeb8 0xffffffffa01ca8b6 [stap_10856]_stp_proc_write_cmd+0x84 (0x1000dad2380, 0x7fbffff310, 0x8, 0x100497fbf48, 0x100497fbf54)
0x100497fbf18 0xffffffff8017e4f4 vfs_write+0xd9
0x100497fbf78 0xffffffff8017e5f1 sys_write+0x48


this is using the latest stap built from the CVS as of this morning.

Known problem or shall I try to debug it?

Kind regards
Tigran

On Mon, 12 Sep 2005, Tigran Aivazian wrote:

Hi,

I attempted to use systemtap 0.3 with modules and wrote trivial two-liner stp script:

probe module("tmod").function("*@tmod.c") { log ("enter") }
probe module("tmod").function("*@tmod.c").return { log ("exit") }

where tmod.c is a short module containing a single function called by both ->init() and ->exit() entry points. I compile it with "-g" and also readelf -w kmod.ko shows that all DWARF2 debug info is present. However stap complains claiming it is missing:

# lsmod | grep tmod
tmod 3584 0
# stap tmod.stp
WARNING: no dwarf info found for module tmod
semantic error: no match for probe point
while: resolving probe point module("tmod").function("*@tmod.c")
WARNING: no dwarf info found for module tmod
semantic error: no match for probe point
while: resolving probe point module("tmod").function("*@tmod.c").return
Pass 2: analysis failed. Try again with '-v' (verbose) option.


This is on x86_64 architecture and 2.6.9-16.ELsmp kernel (of RHEL4 update2).

Any ideas what is it that I am obviously doing wrong? (I have read the arch-0505 paper according to which my 2-liner script seems fine, i.e. both the probe family and probe points are specified correctly).

Kind regards
Tigran

Here is tmod.c:

# cat tmod.c
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/module.h>

MODULE_DESCRIPTION("Test module");
MODULE_AUTHOR("Tigran Aivazian <tigran_aivazian@symantec.com>");
MODULE_LICENSE("GPL");

int tmod_func(int x)
{
       printk(KERN_INFO "tmod: tmod_func(%d)\n", x);
       return 0;
}

static int __init tmod_init(void)
{
       tmod_func(0);
       printk(KERN_INFO "tmod: ->init()\n");
       return 0;
}

static void __exit tmod_exit(void)
{
       tmod_func(1);
       printk(KERN_INFO "tmod: ->exit()\n");
}

module_init(tmod_init)
module_exit(tmod_exit)

EXPORT_SYMBOL(tmod_func);



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