xnu-2422.110.17.tar.gz

[apple/xnu.git] / bsd / dev / dtrace / systrace.c

diff --git a/bsd/dev/dtrace/systrace.c b/bsd/dev/dtrace/systrace.c
index 74ab8a10566aa33a895eb0ea55ac718775e6856d..cdd5a304063d69d4a0b1863f38e78e96f8dd3d8f 100644 (file)
--- a/bsd/dev/dtrace/systrace.c
+++ b/bsd/dev/dtrace/systrace.c
@@ -19,7 +19,7 @@
  * CDDL HEADER END
  */
 /*
  * CDDL HEADER END
  */
 /*

- * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
+ * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.

  * Use is subject to license terms.
  */
 
  * Use is subject to license terms.
  */
 


@@ -43,17 +43,15 @@
 #endif
 #endif
 
 #endif
 #endif
 

-#define MACH__POSIX_C_SOURCE_PRIVATE 1 /* pulls in suitable savearea from mach/ppc/thread_status.h */

 #include <kern/thread.h>
 #include <mach/thread_status.h>
 #include <kern/thread.h>
 #include <mach/thread_status.h>

+

 /* XXX All of these should really be derived from syscall_sw.h */
 /* XXX All of these should really be derived from syscall_sw.h */

-#if defined(__i386__) || defined (__x86_64__)
+#if defined (__x86_64__)

 #define SYSCALL_CLASS_SHIFT 24
 #define SYSCALL_CLASS_MASK  (0xFF << SYSCALL_CLASS_SHIFT)
 #define SYSCALL_NUMBER_MASK (~SYSCALL_CLASS_MASK)
 #define I386_SYSCALL_NUMBER_MASK (0xFFFF)
 #define SYSCALL_CLASS_SHIFT 24
 #define SYSCALL_CLASS_MASK  (0xFF << SYSCALL_CLASS_SHIFT)
 #define SYSCALL_NUMBER_MASK (~SYSCALL_CLASS_MASK)
 #define I386_SYSCALL_NUMBER_MASK (0xFFFF)

-
-typedef x86_saved_state_t savearea_t;

 #endif
 
 #include <sys/param.h>
 #endif
 
 #include <sys/param.h>


@@ -73,10 +71,9 @@ typedef x86_saved_state_t savearea_t;
 #include <sys/conf.h>
 #include <sys/user.h>
 
 #include <sys/conf.h>
 #include <sys/user.h>
 

-#if defined (__ppc__) || defined (__ppc64__)
-#define        SYSTRACE_ARTIFICIAL_FRAMES      3
-#define MACHTRACE_ARTIFICIAL_FRAMES 4
-#elif defined(__i386__) || defined (__x86_64__)
+#include <machine/pal_routines.h>
+
+#if defined (__x86_64__)

 #define        SYSTRACE_ARTIFICIAL_FRAMES      2
 #define MACHTRACE_ARTIFICIAL_FRAMES 3
 #else
 #define        SYSTRACE_ARTIFICIAL_FRAMES      2
 #define MACHTRACE_ARTIFICIAL_FRAMES 3
 #else


@@ -96,23 +93,26 @@ extern const char *syscallnames[];
 #define LOADABLE_SYSCALL(a) 0 /* Not pertinent to Darwin. */
 #define LOADED_SYSCALL(a) 1 /* Not pertinent to Darwin. */
 
 #define LOADABLE_SYSCALL(a) 0 /* Not pertinent to Darwin. */
 #define LOADED_SYSCALL(a) 1 /* Not pertinent to Darwin. */
 

+extern lck_attr_t* dtrace_lck_attr;
+extern lck_grp_t* dtrace_lck_grp;
+static lck_mtx_t       dtrace_systrace_lock;           /* probe state lock */
+

 systrace_sysent_t *systrace_sysent = NULL;
 systrace_sysent_t *systrace_sysent = NULL;

-void (*systrace_probe)(dtrace_id_t, uint64_t, uint64_t,
-    uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t);
+void (*systrace_probe)(dtrace_id_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t);
+
+static uint64_t systrace_getarg(void *, dtrace_id_t, void *, int, int);        

 
 void
 systrace_stub(dtrace_id_t id, uint64_t arg0, uint64_t arg1,
 
 void
 systrace_stub(dtrace_id_t id, uint64_t arg0, uint64_t arg1,

-    uint64_t arg2, uint64_t arg3, uint64_t arg4, uint64_t arg5, uint64_t arg6, uint64_t arg7)
+    uint64_t arg2, uint64_t arg3, uint64_t arg4)

 {
 {

-#pragma unused(id,arg0,arg1,arg2,arg3,arg4,arg5,arg6,arg7)
+#pragma unused(id,arg0,arg1,arg2,arg3,arg4)

 }
 
 }
 

-

 int32_t
 dtrace_systrace_syscall(struct proc *pp, void *uap, int *rv)
 {
 int32_t
 dtrace_systrace_syscall(struct proc *pp, void *uap, int *rv)
 {

-       boolean_t           flavor;
-       unsigned short      code;
+       unsigned short      code;       /* The system call number */

 
        systrace_sysent_t *sy;
        dtrace_id_t id;
 
        systrace_sysent_t *sy;
        dtrace_id_t id;


@@ -122,24 +122,9 @@ dtrace_systrace_syscall(struct proc *pp, void *uap, int *rv)
 #endif
        syscall_arg_t *ip = (syscall_arg_t *)uap;
 
 #endif
        syscall_arg_t *ip = (syscall_arg_t *)uap;
 

-#if defined (__ppc__) || defined (__ppc64__)
-       {
-               savearea_t *regs = (savearea_t *)find_user_regs(current_thread());
-
-               flavor = (((unsigned int)regs->save_r0) == 0)? 1: 0;
-
-               if (flavor)
-                       code = regs->save_r3;
-               else
-                       code = regs->save_r0;
-
-               /*
-                * FIXME: unix_syscall screens for "unsafe calls" and instead calls nosys(), *not* sysent[code] !
-                */
-       }
-#elif defined(__i386__) || defined (__x86_64__)
-#pragma unused(flavor)
+#if defined (__x86_64__)

        {
        {

+               pal_register_cache_state(current_thread(), VALID);

                x86_saved_state_t   *tagged_regs = (x86_saved_state_t *)find_user_regs(current_thread());
 
                if (is_saved_state64(tagged_regs)) {
                x86_saved_state_t   *tagged_regs = (x86_saved_state_t *)find_user_regs(current_thread());
 
                if (is_saved_state64(tagged_regs)) {


@@ -169,10 +154,17 @@ dtrace_systrace_syscall(struct proc *pp, void *uap, int *rv)
        sy = (code >= NUM_SYSENT) ? &systrace_sysent[63] : &systrace_sysent[code];
 
        if ((id = sy->stsy_entry) != DTRACE_IDNONE) {
        sy = (code >= NUM_SYSENT) ? &systrace_sysent[63] : &systrace_sysent[code];
 
        if ((id = sy->stsy_entry) != DTRACE_IDNONE) {

+               uthread_t uthread = (uthread_t)get_bsdthread_info(current_thread());            
+               if (uthread)
+                       uthread->t_dtrace_syscall_args = (void *)ip;
+               

                if (ip)
                if (ip)

-                       (*systrace_probe)(id, *ip, *(ip+1), *(ip+2), *(ip+3), *(ip+4), *(ip+5), *(ip+6), *(ip+7));
+                       (*systrace_probe)(id, *ip, *(ip+1), *(ip+2), *(ip+3), *(ip+4));

                else
                else

-                       (*systrace_probe)(id, 0, 0, 0, 0, 0, 0, 0, 0);
+                       (*systrace_probe)(id, 0, 0, 0, 0, 0);
+               
+               if (uthread)
+                       uthread->t_dtrace_syscall_args = (void *)0;

        }
 
 #if 0 /* XXX */
        }
 
 #if 0 /* XXX */


@@ -260,7 +252,7 @@ dtrace_systrace_syscall(struct proc *pp, void *uap, int *rv)
                 * 
                 * This change was made 4/23/2003 according to the DTrace project's putback log."
                 */ 
                 * 
                 * This change was made 4/23/2003 according to the DTrace project's putback log."
                 */ 

-               (*systrace_probe)(id, munged_rv0, munged_rv0, munged_rv1, (uint64_t)rval, 0, 0, 0, 0);
+               (*systrace_probe)(id, munged_rv0, munged_rv0, munged_rv1, (uint64_t)rval, 0);

        }
 
        return (rval);
        }
 
        return (rval);


@@ -328,7 +320,7 @@ dtrace_systrace_syscall_return(unsigned short code, int rval, int *rv)
                        munged_rv1 = 0LL;
                }
 
                        munged_rv1 = 0LL;
                }
 

-               (*systrace_probe)(id, munged_rv0, munged_rv0, munged_rv1, (uint64_t)rval, 0, 0, 0, 0);
+               (*systrace_probe)(id, munged_rv0, munged_rv0, munged_rv1, (uint64_t)rval, 0);

        }
 }
 #endif /* __APPLE__ */
        }
 }
 #endif /* __APPLE__ */


@@ -409,6 +401,7 @@ systrace_init(struct sysent *actual, systrace_sysent_t **interposed)
                s->stsy_underlying = a->sy_callc;
                s->stsy_return_type = a->sy_return_type;
        }
                s->stsy_underlying = a->sy_callc;
                s->stsy_return_type = a->sy_return_type;
        }

+       lck_mtx_init(&dtrace_systrace_lock, dtrace_lck_grp, dtrace_lck_attr);

 }
 
 #endif /* __APPLE__ */
 }
 
 #endif /* __APPLE__ */


@@ -482,7 +475,7 @@ systrace_destroy(void *arg, dtrace_id_t id, void *parg)
 }
 
 /*ARGSUSED*/
 }
 
 /*ARGSUSED*/

-static void
+static int

 systrace_enable(void *arg, dtrace_id_t id, void *parg)
 {
 #pragma unused(arg) /* __APPLE__ */
 systrace_enable(void *arg, dtrace_id_t id, void *parg)
 {
 #pragma unused(arg) /* __APPLE__ */


@@ -505,17 +498,21 @@ systrace_enable(void *arg, dtrace_id_t id, void *parg)
 
        if (enabled) {
                ASSERT(sysent[sysnum].sy_callc == dtrace_systrace_syscall);
 
        if (enabled) {
                ASSERT(sysent[sysnum].sy_callc == dtrace_systrace_syscall);

-               return;
+               return(0);

        }
        }

-
-       (void) casptr(&sysent[sysnum].sy_callc,
-           (void *)systrace_sysent[sysnum].stsy_underlying,
-           (void *)dtrace_systrace_syscall);

 #ifdef _SYSCALL32_IMPL
        (void) casptr(&sysent32[sysnum].sy_callc,
            (void *)systrace_sysent32[sysnum].stsy_underlying,
            (void *)dtrace_systrace_syscall32);
 #endif
 #ifdef _SYSCALL32_IMPL
        (void) casptr(&sysent32[sysnum].sy_callc,
            (void *)systrace_sysent32[sysnum].stsy_underlying,
            (void *)dtrace_systrace_syscall32);
 #endif

+
+       lck_mtx_lock(&dtrace_systrace_lock);
+       if (sysent[sysnum].sy_callc == systrace_sysent[sysnum].stsy_underlying) {
+               vm_offset_t dss = (vm_offset_t)&dtrace_systrace_syscall;
+               ml_nofault_copy((vm_offset_t)&dss, (vm_offset_t)&sysent[sysnum].sy_callc, sizeof(vm_offset_t));
+       }
+       lck_mtx_unlock(&dtrace_systrace_lock);
+       return (0);

 }
 
 /*ARGSUSED*/
 }
 
 /*ARGSUSED*/


@@ -529,9 +526,10 @@ systrace_disable(void *arg, dtrace_id_t id, void *parg)
            systrace_sysent[sysnum].stsy_return == DTRACE_IDNONE);
 
        if (disable) {
            systrace_sysent[sysnum].stsy_return == DTRACE_IDNONE);
 
        if (disable) {

-               (void) casptr(&sysent[sysnum].sy_callc,
-                   (void *)dtrace_systrace_syscall,
-                   (void *)systrace_sysent[sysnum].stsy_underlying);
+               lck_mtx_lock(&dtrace_systrace_lock);
+               if (sysent[sysnum].sy_callc == dtrace_systrace_syscall)
+                       ml_nofault_copy((vm_offset_t)&systrace_sysent[sysnum].stsy_underlying, (vm_offset_t)&sysent[sysnum].sy_callc, sizeof(systrace_sysent[sysnum].stsy_underlying));
+               lck_mtx_unlock(&dtrace_systrace_lock);

 
 #ifdef _SYSCALL32_IMPL
                (void) casptr(&sysent32[sysnum].sy_callc,
 
 #ifdef _SYSCALL32_IMPL
                (void) casptr(&sysent32[sysnum].sy_callc,


@@ -569,7 +567,7 @@ static dtrace_pops_t systrace_pops = {
        NULL,
        NULL,
        NULL,
        NULL,
        NULL,
        NULL,

-       NULL,
+       systrace_getarg,

        NULL,
        systrace_destroy
 };
        NULL,
        systrace_destroy
 };


@@ -738,22 +736,18 @@ typedef kern_return_t (*mach_call_t)(void *);
 typedef void    mach_munge_t(const void *, void *);
 
 typedef struct {
 typedef void    mach_munge_t(const void *, void *);
 
 typedef struct {

-        int                     mach_trap_arg_count;
-        int                     (*mach_trap_function)(void);
-#if defined(__i386__)
-        boolean_t               mach_trap_stack;
-#else
-        mach_munge_t            *mach_trap_arg_munge32; /* system call arguments for 32-bit */
-        mach_munge_t            *mach_trap_arg_munge64; /* system call arguments for 64-bit */
+       int                     mach_trap_arg_count;
+       kern_return_t           (*mach_trap_function)(void *);
+#if defined(__x86_64__)
+       mach_munge_t            *mach_trap_arg_munge32; /* system call arguments for 32-bit */

 #endif
 #endif

-#if     !MACH_ASSERT
-        int                     mach_trap_unused;
-#else
-        const char*             mach_trap_name;
-#endif /* !MACH_ASSERT */
+       int                     mach_trap_u32_words;
+#if    MACH_ASSERT
+       const char*             mach_trap_name;
+#endif /* MACH_ASSERT */

 } mach_trap_t;
 
 } mach_trap_t;
 

-extern mach_trap_t              mach_trap_table[];
+extern const mach_trap_t              mach_trap_table[]; /* syscall_sw.h now declares this as const */

 extern int                      mach_trap_count;
 
 extern const char *mach_syscall_name_table[];
 extern int                      mach_trap_count;
 
 extern const char *mach_syscall_name_table[];


@@ -778,21 +772,27 @@ struct mach_call_args {
 #error 1 << SYSTRACE_SHIFT must exceed number of Mach traps
 #endif
 
 #error 1 << SYSTRACE_SHIFT must exceed number of Mach traps
 #endif
 

-typedef systrace_sysent_t machtrace_sysent_t;
+typedef struct machtrace_sysent {
+       dtrace_id_t     stsy_entry;
+       dtrace_id_t     stsy_return;
+       kern_return_t   (*stsy_underlying)(void *);
+       int32_t         stsy_return_type;
+} machtrace_sysent_t;

 
 static machtrace_sysent_t *machtrace_sysent = NULL;
 
 void (*machtrace_probe)(dtrace_id_t, uint64_t, uint64_t,
     uint64_t, uint64_t, uint64_t);
 
 
 static machtrace_sysent_t *machtrace_sysent = NULL;
 
 void (*machtrace_probe)(dtrace_id_t, uint64_t, uint64_t,
     uint64_t, uint64_t, uint64_t);
 

+static uint64_t machtrace_getarg(void *, dtrace_id_t, void *, int, int);       
+

 static dev_info_t *machtrace_devi;
 static dtrace_provider_id_t machtrace_id;
 
 static kern_return_t
 dtrace_machtrace_syscall(struct mach_call_args *args)
 {
 static dev_info_t *machtrace_devi;
 static dtrace_provider_id_t machtrace_id;
 
 static kern_return_t
 dtrace_machtrace_syscall(struct mach_call_args *args)
 {

-       boolean_t           flavor;
-       unsigned short      code;
+       int code;       /* The mach call number */

 
        machtrace_sysent_t *sy;
        dtrace_id_t id;
 
        machtrace_sysent_t *sy;
        dtrace_id_t id;


@@ -803,20 +803,9 @@ dtrace_machtrace_syscall(struct mach_call_args *args)
        syscall_arg_t *ip = (syscall_arg_t *)args;
        mach_call_t mach_call;
 
        syscall_arg_t *ip = (syscall_arg_t *)args;
        mach_call_t mach_call;
 

-#if defined (__ppc__) || defined (__ppc64__)
-       {
-               savearea_t *regs = (savearea_t *)find_user_regs(current_thread());
-
-               flavor = (((unsigned int)regs->save_r0) == 0)? 1: 0;
-
-               if (flavor)
-                       code = -regs->save_r3;
-               else
-                       code = -regs->save_r0;
-       }
-#elif defined(__i386__) || defined (__x86_64__)
-#pragma unused(flavor)
+#if defined (__x86_64__)

        {
        {

+               pal_register_cache_state(current_thread(), VALID);

                x86_saved_state_t   *tagged_regs = (x86_saved_state_t *)find_user_regs(current_thread());
 
                if (is_saved_state64(tagged_regs)) {
                x86_saved_state_t   *tagged_regs = (x86_saved_state_t *)find_user_regs(current_thread());
 
                if (is_saved_state64(tagged_regs)) {


@@ -831,8 +820,17 @@ dtrace_machtrace_syscall(struct mach_call_args *args)
 
        sy = &machtrace_sysent[code];
 
 
        sy = &machtrace_sysent[code];
 

-       if ((id = sy->stsy_entry) != DTRACE_IDNONE)
+       if ((id = sy->stsy_entry) != DTRACE_IDNONE) {
+               uthread_t uthread = (uthread_t)get_bsdthread_info(current_thread());    
+
+               if (uthread)
+                       uthread->t_dtrace_syscall_args = (void *)ip;
+               

                (*machtrace_probe)(id, *ip, *(ip+1), *(ip+2), *(ip+3), *(ip+4));
                (*machtrace_probe)(id, *ip, *(ip+1), *(ip+2), *(ip+3), *(ip+4));

+               
+               if (uthread)
+                       uthread->t_dtrace_syscall_args = (void *)0;             
+       }

 
 #if 0 /* XXX */
        /*
 
 #if 0 /* XXX */
        /*


@@ -858,7 +856,7 @@ dtrace_machtrace_syscall(struct mach_call_args *args)
 }
 
 static void
 }
 
 static void

-machtrace_init(mach_trap_t *actual, machtrace_sysent_t **interposed)
+machtrace_init(const mach_trap_t *actual, machtrace_sysent_t **interposed)

 {
        machtrace_sysent_t *msysent = *interposed;
        int i;
 {
        machtrace_sysent_t *msysent = *interposed;
        int i;


@@ -869,16 +867,16 @@ machtrace_init(mach_trap_t *actual, machtrace_sysent_t **interposed)
        }
 
        for (i = 0; i < NSYSCALL; i++) {
        }
 
        for (i = 0; i < NSYSCALL; i++) {

-               mach_trap_t *a = &actual[i];
+               const mach_trap_t *a = &actual[i];

                machtrace_sysent_t *s = &msysent[i];
 
                if (LOADABLE_SYSCALL(a) && !LOADED_SYSCALL(a))
                        continue;
 
                machtrace_sysent_t *s = &msysent[i];
 
                if (LOADABLE_SYSCALL(a) && !LOADED_SYSCALL(a))
                        continue;
 

-               if ((mach_call_t)(a->mach_trap_function) == (mach_call_t)(dtrace_machtrace_syscall))
+               if (a->mach_trap_function == (mach_call_t)(dtrace_machtrace_syscall))

                        continue;
 
                        continue;
 

-               s->stsy_underlying = (sy_call_t *)a->mach_trap_function;
+               s->stsy_underlying = a->mach_trap_function;

        }
 }
 
        }
 }
 


@@ -937,7 +935,7 @@ machtrace_destroy(void *arg, dtrace_id_t id, void *parg)
 }
 
 /*ARGSUSED*/
 }
 
 /*ARGSUSED*/

-static void
+static int

 machtrace_enable(void *arg, dtrace_id_t id, void *parg)
 {
 #pragma unused(arg) /* __APPLE__ */
 machtrace_enable(void *arg, dtrace_id_t id, void *parg)
 {
 #pragma unused(arg) /* __APPLE__ */


@@ -953,13 +951,20 @@ machtrace_enable(void *arg, dtrace_id_t id, void *parg)
        }
 
        if (enabled) {
        }
 
        if (enabled) {

-           ASSERT(sysent[sysnum].sy_callc == (void *)dtrace_machtrace_syscall);
-               return;
+           ASSERT(mach_trap_table[sysnum].mach_trap_function == (void *)dtrace_machtrace_syscall);
+           return(0);
+       }
+
+       lck_mtx_lock(&dtrace_systrace_lock);
+
+       if (mach_trap_table[sysnum].mach_trap_function == machtrace_sysent[sysnum].stsy_underlying) {
+               vm_offset_t dss = (vm_offset_t)&dtrace_machtrace_syscall;
+               ml_nofault_copy((vm_offset_t)&dss, (vm_offset_t)&mach_trap_table[sysnum].mach_trap_function, sizeof(vm_offset_t));

        }
 
        }
 

-       (void) casptr(&mach_trap_table[sysnum].mach_trap_function,
-                     (void *)machtrace_sysent[sysnum].stsy_underlying,
-                     (void *)dtrace_machtrace_syscall);
+       lck_mtx_unlock(&dtrace_systrace_lock);
+
+       return(0);

 }
 
 /*ARGSUSED*/
 }
 
 /*ARGSUSED*/


@@ -973,10 +978,13 @@ machtrace_disable(void *arg, dtrace_id_t id, void *parg)
                        machtrace_sysent[sysnum].stsy_return == DTRACE_IDNONE);
 
        if (disable) {
                        machtrace_sysent[sysnum].stsy_return == DTRACE_IDNONE);
 
        if (disable) {

-               (void) casptr(&mach_trap_table[sysnum].mach_trap_function,
-                             (void *)dtrace_machtrace_syscall,
-                             (void *)machtrace_sysent[sysnum].stsy_underlying);

 
 

+               lck_mtx_lock(&dtrace_systrace_lock);
+
+               if (mach_trap_table[sysnum].mach_trap_function == (mach_call_t)dtrace_machtrace_syscall) {
+                       ml_nofault_copy((vm_offset_t)&machtrace_sysent[sysnum].stsy_underlying, (vm_offset_t)&mach_trap_table[sysnum].mach_trap_function, sizeof(vm_offset_t));
+               }
+               lck_mtx_unlock(&dtrace_systrace_lock);

        }
 
        if (SYSTRACE_ISENTRY((uintptr_t)parg)) {
        }
 
        if (SYSTRACE_ISENTRY((uintptr_t)parg)) {


@@ -1002,7 +1010,7 @@ static dtrace_pops_t machtrace_pops = {
        NULL,
        NULL,
        NULL,
        NULL,
        NULL,
        NULL,

-       NULL,
+       machtrace_getarg,

        NULL,
        machtrace_destroy
 };
        NULL,
        machtrace_destroy
 };


@@ -1104,3 +1112,49 @@ void systrace_init( void )
 }
 #undef SYSTRACE_MAJOR
 #endif /* __APPLE__ */
 }
 #undef SYSTRACE_MAJOR
 #endif /* __APPLE__ */

+
+static uint64_t
+systrace_getarg(void *arg, dtrace_id_t id, void *parg, int argno, int aframes)
+{
+#pragma unused(arg,id,parg,aframes)     /* __APPLE__ */
+       uint64_t val = 0;
+       syscall_arg_t *stack = (syscall_arg_t *)NULL;
+
+       uthread_t uthread = (uthread_t)get_bsdthread_info(current_thread());    
+
+       if (uthread)
+               stack = (syscall_arg_t *)uthread->t_dtrace_syscall_args;
+
+       if (!stack)
+               return(0);
+
+       DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
+       /* dtrace_probe arguments arg0 .. arg4 are 64bits wide */
+       val = (uint64_t)*(stack+argno);
+       DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
+       return (val);
+}
+
+
+static uint64_t
+machtrace_getarg(void *arg, dtrace_id_t id, void *parg, int argno, int aframes)
+{
+#pragma unused(arg,id,parg,aframes)     /* __APPLE__ */
+       uint64_t val = 0;
+       syscall_arg_t *stack = (syscall_arg_t *)NULL;
+
+       uthread_t uthread = (uthread_t)get_bsdthread_info(current_thread());
+       
+       if (uthread)
+               stack = (syscall_arg_t *)uthread->t_dtrace_syscall_args;
+       
+       if (!stack)
+               return(0);
+
+       DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
+       /* dtrace_probe arguments arg0 .. arg4 are 64bits wide */
+       val = (uint64_t)*(stack+argno); 
+       DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
+       return (val);
+}
+