[ltt-dev] LTTng 2.0 on ARM

[avik.sil@linaro.org (Avik Sil)]

> Hi Avik,
> 
> Can I get your kernel .config ? Also, adding a printk in lttng-modules
> wrapper/vmalloc.h, just after vmalloc_sync_all_sym = (void *)
> kallsyms_lookup_name("vmalloc_sync_all");
> 
> printing the vmalloc_sync_all_sym pointer value would be clearly
> helpful. I would think ARM does not implement vmalloc_sync_all, so the
> dummy mm/vmalloc.c vmalloc_sync_all weak symbol should be used as a
> valid empty function. Please grep for vmalloc_sync_all under your
> arch/arm to see if your particular omap flavor is implementing a
> vmalloc_sync_all.
> 
Hi Mathieu,

Please find attached my kernel .config. After adding printk just after
vmalloc_sync_all_sym = (void *)kallsyms_lookup_name("vmalloc_sync_all");
I got following output:

[ 1139.173522] vmalloc_sync_all_sym: c00a1d14
[ 1139.180877] Internal error: Oops - undefined instruction: 0 [#1]
PREEMPT SMP
[ 1139.191284] Modules linked in: lttng_ftrace(+)
[ 1139.198974] CPU: 1    Not tainted  (3.0.0-1004-linaro-omap #6)
[ 1139.208099] PC is at vmalloc_sync_all+0x0/0x8
[ 1139.215667] LR is at init_module+0x1c/0x28 [lttng_ftrace]
[ 1139.224304] pc : [<c00a1d14>]    lr : [<bf800211>]    psr: 60000113
[ 1139.224304] sp : ebb11f50  ip : 00000000  fp : 00000000
[ 1139.242401] r10: 00000000  r9 : 00000000  r8 : c06a2f00
[ 1139.250793] r7 : bf8001f5  r6 : 00000000  r5 : 00182008  r4 : c00a1d14
[ 1139.260559] r3 : 271aed1f  r2 : ebb11f44  r1 : bf8003a6  r0 : 00000034
[ 1139.270233] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM
Segment user
[ 1139.280670] Control: 50c5387d  Table: abdb004a  DAC: 00000015
[ 1139.289672] Process insmod (pid: 1368, stack limit = 0xebb102f8)
[ 1139.298889] Stack: (0xebb11f50 to 0xebb12000)
[ 1139.306335] 1f40:                                     bf80044c
c00085f7 00000000 00000001
[ 1139.320587] 1f60: bf80044c bf80044c 00182008 bf80044c 00182008
00000000 000019de c000c364
[ 1139.334899] 1f80: ebb10000 c00622bb 00182018 000019de 00182008
00000002 000019de beb099a0
[ 1139.349273] 1fa0: 00000080 c000c161 00000002 000019de 00182018
000019de 00182008 402e6250
[ 1139.363861] 1fc0: 00000002 000019de beb099a0 00000080 00000003
00004000 400b9000 00000000
[ 1139.378540] 1fe0: 00011f80 beb09728 00008c01 40296ae0 00000110
00182018 a92aabaa aab0b0aa
[ 1139.393310] [<c00a1d14>] (vmalloc_sync_all+0x0/0x8) from [<bf800211>]
(init_module+0x1c/0x28 [lttng_ftrace])
[ 1139.410095] [<bf800211>] (init_module+0x1c/0x28 [lttng_ftrace]) from
[<c00085f7>] (do_one_initcall+0x6b/0xfc)
[ 1139.427032] [<c00085f7>] (do_one_initcall+0x6b/0xfc) from
[<c00622bb>] (sys_init_module+0x4b/0x11c)
[ 1139.443176] [<c00622bb>] (sys_init_module+0x4b/0x11c) from
[<c000c161>] (ret_fast_syscall+0x1/0x50)
[ 1139.459472] Code: e8bdb007 bf008ff0 c0672290 c0be2e54 (f85db500)
[ 1139.475524] ---[ end trace 7f9f02516cb400bf ]---
Segmentation fault

Also I found that vmalloc_sync_all is not implemented under arch/arm and
it is using the mm/vmalloc.c vmalloc_sync_all weak symbol whose
disassembly gives:

bx	lr

Regards,
Avik

> Thanks!
> 
> Mathieu
> 
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