Unsuccessfull system call interception. Please, help to correct it or make a suggestion.

Platform: IBM Spruce 750CX.
The problem: due to the necessity of logging system calls entry/exit events by LTT the arch/ppc/kernel/entry.S was modified in this way:

/* LTT stuff */
#if (CONFIG_LTT)

#define TRACE_REAL_ASM_SYSCALL_ENTRY \
addi r3,r1,STACK_FRAME_OVERHEAD; /* Put pointer to
registers into r3 */ \

       mflr    r29;                            /* Save LR */ \
       bl      trace_real_syscall_entry;       /* Call real trace
function */ \
       mtlr    r29;                            /* Restore LR */ \
       lwz     r0,GPR0(r1);                    /* Restore original
registers */ \
       lwz     r3,GPR3(r1);    \
       lwz     r4,GPR4(r1);    \
       lwz     r5,GPR5(r1);    \
       lwz     r6,GPR6(r1);    \
       lwz     r7,GPR7(r1);    \
       lwz     r8,GPR8(r1);

#define TRACE_REAL_ASM_SYSCALL_EXIT \
bl trace_real_syscall_exit; /* Call real trace
function */ \
lwz r0,GPR0(r1); /* Restore original

registers */ \
       lwz     r3,RESULT(r1); \
       lwz     r4,GPR4(r1); \
       lwz     r5,GPR5(r1); \
       lwz     r6,GPR6(r1); \
       lwz     r7,GPR7(r1); \
       lwz     r8,GPR8(r1); \
       addi    r9,r1,STACK_FRAME_OVERHEAD;

#endif /* CONFIG_LTT */

And then:

_GLOBAL(DoSyscall)

       stw     r0,THREAD+LAST_SYSCALL(r2)
       stw     r3,ORIG_GPR3(r1)
       li      r12,0
       stw     r12,RESULT(r1)
       lwz     r11,_CCR(r1)    /* Clear SO bit in CR */
       rlwinm  r11,r11,0,4,2
       stw     r11,_CCR(r1)
#ifdef SHOW_SYSCALLS
       bl      do_show_syscall
#endif /* SHOW_SYSCALLS */
       rlwinm  r10,r1,0,0,18   /* current_thread_info() */
       lwz     r11,TI_LOCAL_FLAGS(r10)
       rlwinm  r11,r11,0,~_TIFL_FORCE_NOERROR
       stw     r11,TI_LOCAL_FLAGS(r10)
       lwz     r11,TI_FLAGS(r10)
       andi.   r11,r11,_TIF_SYSCALL_TRACE
       bne-    syscall_dotrace
syscall_dotrace_cont:
       cmpli   0,r0,NR_syscalls
       lis     r10,sys_call_table@h
       ori     r10,r10,sys_call_table@l
       slwi    r0,r0,2
       bge-    66f
       lwzx    r10,r10,r0      /* Fetch system call handler [ptr] */
       mtlr    r10
#if (CONFIG_LTT)
       TRACE_REAL_ASM_SYSCALL_ENTRY ;

#endif
addi r9,r1,STACK_FRAME_OVERHEAD
blrl /* Call handler */
.globl ret_from_syscall
ret_from_syscall:
#ifdef SHOW_SYSCALLS
bl do_show_syscall_exit
#endif
#if (CONFIG_LTT)
stw r3,RESULT(r1) /* Save result */
TRACE_REAL_ASM_SYSCALL_EXIT ;

#endif
       mr      r6,r3
       li      r11,-_LAST_ERRNO
       cmpl    0,r3,r11
       rlwinm  r12,r1,0,0,18   /* current_thread_info() */
       blt+    30f
       lwz     r11,TI_LOCAL_FLAGS(r12)
       andi.   r11,r11,_TIFL_FORCE_NOERROR
       bne     30f

And so on.

This state of affairs produces the next fault sequence (obtained with BDI2000 help):
(gdb) bt
#0 0xc000814c in __delay ()
#1 0xc0015ac4 in panic (fmt=0x121eac0 <Address 0x121eac0 out of bounds>)
at delay.h:42
#2 0xc00182b0 in do_exit (code=11) at kernel/exit.c:768
#3 0xc000625c in die (str=0x1 <Address 0x1 out of bounds>, fp=0xc02add20,

       err=11) at arch/ppc/kernel/traps.c:106
#4  0xc000e51c in bad_page_fault (regs=0xc02add20, address=1, sig=11)
   at arch/ppc/mm/fault.c:363
#5  0xc000e4c0 in do_page_fault (regs=0xc02add20, address=2449539152,
              error_code=1107296256) at arch/ppc/mm/fault.c:337
#6  0xc0005f80 in ret_from_except_full () at init/initramfs.c:12
#7  0xc01c8ce0 in init_thread_union ()
#8  0xc0025e94 in queue_work (wq=0x1, work=0x1) at kernel/workqueue.c:105
#9  0xc0026698 in schedule_work (work=0x1) at kernel/workqueue.c:389
#10 0xc002a1d4 in kthread_create (threadfn=0x593ad, data=0x1,
                   namefmt=0xc017388c "%s/%d") at kernel/kthread.c:134

#11 0xc002640c in create_workqueue_thread (wq=0x1, cpu=10)
at kernel/workqueue.c:293
#12 0xc0026528 in __create_workqueue (name=0xc017fe74 "kblockd",
singlethread=0) at kernel/workqueue.c:329
#13 0xc01d8d6c in blk_dev_init () at drivers/block/ll_rw_blk.c:2822 #14 0xc01d8e28 in device_init () at drivers/block/genhd.c:311 #15 0xc01ca664 in do_initcalls () at init/main.c:519
#16 0xc01ca700 in do_basic_setup () at init/main.c:559 #17 0xc000392c in init (unused=0x593ad) at init/main.c:599 #18 0xc0008994 in original_kernel_thread ()

The investigation has shown that the reason for fault is the
addi r3,r1,STACK_FRAME_OVERHEAD; /* Put pointer to registers into
r3 */ \
instruction whitch follows directly after the macro:
#define TRACE_REAL_ASM_SYSCALL_ENTRY

Definitly I can't just get rid of it (trace_real_syscall_entry really needs a parameter) and my poor knowledge of ppc assembly prevents me from thorough understanding of DoSyscall. If you have a clue, or think you may know what problem is, please let me know ASAP.

Thanks in advance
Yuri Frolov

** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/

First, you don't say whether you are working on 2.4 or 2.6.

Secondly, why can't you use the existing syscall trace infrastructure?

Paul.

** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/

I'm working on linux-2.6.
I can't use the existing syscall trace infrastructure due to the necessity to get LTT syscall interception mechanism working (LTT has specific routines and binary format it uses to save info about syscall entry/exit, I can't just get rid of it).
I would be happy to address this problem someone who subscribed to the LTT mailing list, but seems the development of LTT tends to be more x86 centric. I posted the message because my strong opinion that the problem is in the interaction between common ppc syscall handling mechanism and the LTT portion which both written on pure ppc assembly...

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