]> git.saurik.com Git - apple/xnu.git/blobdiff - bsd/dev/i386/systemcalls.c
xnu-6153.61.1.tar.gz
[apple/xnu.git] / bsd / dev / i386 / systemcalls.c
index e6e995ac6e69f6d82bd4c0ba93377700c9caca20..a5a7255bdf20b7e3623ea688c6d9771e1920c169 100644 (file)
@@ -2,7 +2,7 @@
  * Copyright (c) 2000-2016 Apple Inc. All rights reserved.
  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
- * 
+ *
  * This file contains Original Code and/or Modifications of Original Code
  * as defined in and that are subject to the Apple Public Source License
  * Version 2.0 (the 'License'). You may not use this file except in
  * unlawful or unlicensed copies of an Apple operating system, or to
  * circumvent, violate, or enable the circumvention or violation of, any
  * terms of an Apple operating system software license agreement.
- * 
+ *
  * Please obtain a copy of the License at
  * http://www.opensource.apple.com/apsl/ and read it before using this file.
- * 
+ *
  * The Original Code and all software distributed under the License are
  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
@@ -22,7 +22,7 @@
  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  * Please see the License for the specific language governing rights and
  * limitations under the License.
- * 
+ *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  */
 #include <kern/task.h>
@@ -34,7 +34,6 @@
 #include <kern/debug.h>
 #include <mach/machine/thread_status.h>
 #include <mach/thread_act.h>
-#include <mach/branch_predicates.h>
 
 #include <sys/kernel.h>
 #include <sys/vm.h>
@@ -48,6 +47,7 @@
 #include <sys/sysproto.h>
 #include <sys/kauth.h>
 #include <sys/systm.h>
+#include <sys/bitstring.h>
 
 #include <security/audit/audit.h>
 
 
 #include <machine/pal_routines.h>
 
+#if CONFIG_MACF
+#include <security/mac_framework.h>
+#endif
+
 #if CONFIG_DTRACE
 extern int32_t dtrace_systrace_syscall(struct proc *, void *, int *);
 extern void dtrace_systrace_syscall_return(unsigned short, int, int *);
@@ -70,8 +74,8 @@ extern void *find_user_regs(thread_t);
 extern const char *syscallnames[];
 
 #define code_is_kdebug_trace(code) (((code) == SYS_kdebug_trace) ||   \
-                                    ((code) == SYS_kdebug_trace64) || \
-                                    ((code) == SYS_kdebug_trace_string))
+                                   ((code) == SYS_kdebug_trace64) || \
+                                   ((code) == SYS_kdebug_trace_string))
 
 /*
  * Function:   unix_syscall
@@ -84,64 +88,67 @@ __attribute__((noreturn))
 void
 unix_syscall(x86_saved_state_t *state)
 {
-       thread_t                thread;
-       void                    *vt;
-       unsigned int            code;
-       struct sysent           *callp;
-
-       int                     error;
-       vm_offset_t             params;
-       struct proc             *p;
-       struct uthread          *uthread;
-       x86_saved_state32_t     *regs;
-       boolean_t               is_vfork;
+       thread_t                thread;
+       void                    *vt;
+       unsigned int            code, syscode;
+       struct sysent           *callp;
+
+       int                     error;
+       vm_offset_t             params;
+       struct proc             *p;
+       struct uthread          *uthread;
+       x86_saved_state32_t     *regs;
+       boolean_t               is_vfork;
+       pid_t                   pid;
 
        assert(is_saved_state32(state));
        regs = saved_state32(state);
 #if DEBUG
-       if (regs->eax == 0x800)
+       if (regs->eax == 0x800) {
                thread_exception_return();
+       }
 #endif
        thread = current_thread();
        uthread = get_bsdthread_info(thread);
 
-#if PROC_REF_DEBUG
        uthread_reset_proc_refcount(uthread);
-#endif
 
        /* Get the approriate proc; may be different from task's for vfork() */
        is_vfork = uthread->uu_flag & UT_VFORK;
-       if (__improbable(is_vfork != 0))
+       if (__improbable(is_vfork != 0)) {
                p = current_proc();
-       else 
+       } else {
                p = (struct proc *)get_bsdtask_info(current_task());
+       }
 
-       code = regs->eax & I386_SYSCALL_NUMBER_MASK;
+       code    = regs->eax & I386_SYSCALL_NUMBER_MASK;
+       syscode = (code < nsysent) ? code : SYS_invalid;
        DEBUG_KPRINT_SYSCALL_UNIX("unix_syscall: code=%d(%s) eip=%u\n",
-                                                         code, syscallnames[code >= nsysent ? SYS_invalid : code], (uint32_t)regs->eip);
-       params = (vm_offset_t) (regs->uesp + sizeof (int));
+           code, syscallnames[syscode], (uint32_t)regs->eip);
+       params = (vm_offset_t) (regs->uesp + sizeof(int));
 
        regs->efl &= ~(EFL_CF);
 
-       callp = (code >= nsysent) ? &sysent[SYS_invalid] : &sysent[code];
+       callp = &sysent[syscode];
 
        if (__improbable(callp == sysent)) {
                code = fuword(params);
                params += sizeof(int);
-               callp = (code >= nsysent) ? &sysent[SYS_invalid] : &sysent[code];
+               syscode = (code < nsysent) ? code : SYS_invalid;
+               callp = &sysent[syscode];
        }
 
        vt = (void *)uthread->uu_arg;
 
        if (callp->sy_arg_bytes != 0) {
 #if CONFIG_REQUIRES_U32_MUNGING
-               sy_munge_t      *mungerp;
+               sy_munge_t      *mungerp;
 #else
 #error U32 syscalls on x86_64 kernel requires munging
 #endif
-               uint32_t         nargs;
+               uint32_t         nargs;
 
-               assert((unsigned) callp->sy_arg_bytes <= sizeof (uthread->uu_arg));
+               assert((unsigned) callp->sy_arg_bytes <= sizeof(uthread->uu_arg));
                nargs = callp->sy_arg_bytes;
                error = copyin((user_addr_t) params, (char *) vt, nargs);
                if (error) {
@@ -152,23 +159,21 @@ unix_syscall(x86_saved_state_t *state)
                }
 
                if (__probable(!code_is_kdebug_trace(code))) {
-                       int *ip = (int *)vt;
-
-                       KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
-                               BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_START,
-                               *ip, *(ip+1), *(ip+2), *(ip+3), 0);
+                       uint32_t *uip = vt;
+                       KDBG_RELEASE(BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_START,
+                           uip[0], uip[1], uip[2], uip[3]);
                }
 
 #if CONFIG_REQUIRES_U32_MUNGING
                mungerp = callp->sy_arg_munge32;
 
-               if (mungerp != NULL)
+               if (mungerp != NULL) {
                        (*mungerp)(vt);
+               }
 #endif
-       } else
-               KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
-                       BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_START,
-                       0, 0, 0, 0, 0);
+       } else {
+               KDBG_RELEASE(BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_START);
+       }
 
        /*
         * Delayed binding of thread credential to process credential, if we
@@ -180,19 +185,34 @@ unix_syscall(x86_saved_state_t *state)
        uthread->uu_rval[1] = 0;
        uthread->uu_flag |= UT_NOTCANCELPT;
        uthread->syscall_code = code;
+       pid = proc_pid(p);
 
 #ifdef JOE_DEBUG
-        uthread->uu_iocount = 0;
-        uthread->uu_vpindex = 0;
+       uthread->uu_iocount = 0;
+       uthread->uu_vpindex = 0;
 #endif
 
+#if CONFIG_MACF
+       if (__improbable(p->syscall_filter_mask != NULL && !bitstr_test(p->syscall_filter_mask, syscode))) {
+               error = mac_proc_check_syscall_unix(p, syscode);
+               if (error) {
+                       goto skip_syscall;
+               }
+       }
+#endif /* CONFIG_MACF */
+
        AUDIT_SYSCALL_ENTER(code, p, uthread);
        error = (*(callp->sy_call))((void *) p, (void *) vt, &(uthread->uu_rval[0]));
        AUDIT_SYSCALL_EXIT(code, p, uthread, error);
 
+#if CONFIG_MACF
+skip_syscall:
+#endif /* CONFIG_MACF */
+
 #ifdef JOE_DEBUG
-        if (uthread->uu_iocount)
-                printf("system call returned with uu_iocount != 0\n");
+       if (uthread->uu_iocount) {
+               printf("system call returned with uu_iocount != 0\n");
+       }
 #endif
 #if CONFIG_DTRACE
        uthread->t_dtrace_errno = error;
@@ -207,20 +227,19 @@ unix_syscall(x86_saved_state_t *state)
                 */
 
                pal_syscall_restart(thread, state);
-       }
-       else if (error != EJUSTRETURN) {
+       } else if (error != EJUSTRETURN) {
                if (__improbable(error)) {
-                   regs->eax = error;
-                   regs->efl |= EFL_CF;        /* carry bit */
+                       regs->eax = error;
+                       regs->efl |= EFL_CF;    /* carry bit */
                } else { /* (not error) */
-                       /*
-                        * We split retval across two registers, in case the
-                        * syscall had a 64-bit return value, in which case
-                        * eax/edx matches the function call ABI.
-                        */
-                   regs->eax = uthread->uu_rval[0];
-                   regs->edx = uthread->uu_rval[1];
-               } 
+                        /*
+                         * We split retval across two registers, in case the
+                         * syscall had a 64-bit return value, in which case
+                         * eax/edx matches the function call ABI.
+                         */
+                       regs->eax = uthread->uu_rval[0];
+                       regs->edx = uthread->uu_rval[1];
+               }
        }
 
        DEBUG_KPRINT_SYSCALL_UNIX(
@@ -228,9 +247,16 @@ unix_syscall(x86_saved_state_t *state)
                error, regs->eax, regs->edx);
 
        uthread->uu_flag &= ~UT_NOTCANCELPT;
+       uthread->syscall_code = 0;
+
+#if DEBUG || DEVELOPMENT
+       kern_allocation_name_t
+       prior __assert_only = thread_set_allocation_name(NULL);
+       assertf(prior == NULL, "thread_set_allocation_name(\"%s\") not cleared", kern_allocation_get_name(prior));
+#endif /* DEBUG || DEVELOPMENT */
 
        if (__improbable(uthread->uu_lowpri_window)) {
-               /*
+               /*
                 * task is marked as a low priority I/O type
                 * and the I/O we issued while in this system call
                 * collided with normal I/O operations... we'll
@@ -239,10 +265,10 @@ unix_syscall(x86_saved_state_t *state)
                 */
                throttle_lowpri_io(1);
        }
-       if (__probable(!code_is_kdebug_trace(code)))
-               KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
-                       BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_END,
-                       error, uthread->uu_rval[0], uthread->uu_rval[1], p->p_pid, 0);
+       if (__probable(!code_is_kdebug_trace(code))) {
+               KDBG_RELEASE(BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_END,
+                   error, uthread->uu_rval[0], uthread->uu_rval[1], pid);
+       }
 
        if (__improbable(!is_vfork && callp->sy_call == (sy_call_t *)execve && !error)) {
                pal_execve_return(thread);
@@ -262,35 +288,36 @@ __attribute__((noreturn))
 void
 unix_syscall64(x86_saved_state_t *state)
 {
-       thread_t        thread;
-       void                    *vt;
-       unsigned int    code;
-       struct sysent   *callp;
-       int             args_in_regs;
-       boolean_t       args_start_at_rdi;
-       int             error;
-       struct proc     *p;
-       struct uthread  *uthread;
+       thread_t        thread;
+       void                    *vt;
+       unsigned int    code, syscode;
+       struct sysent   *callp;
+       int             args_in_regs;
+       boolean_t       args_start_at_rdi;
+       int             error;
+       struct proc     *p;
+       struct uthread  *uthread;
        x86_saved_state64_t *regs;
+       pid_t           pid;
 
        assert(is_saved_state64(state));
        regs = saved_state64(state);
-#if    DEBUG
-       if (regs->rax == 0x2000800)
+#if     DEBUG
+       if (regs->rax == 0x2000800) {
                thread_exception_return();
+       }
 #endif
        thread = current_thread();
        uthread = get_bsdthread_info(thread);
 
-#if PROC_REF_DEBUG
        uthread_reset_proc_refcount(uthread);
-#endif
 
        /* Get the approriate proc; may be different from task's for vfork() */
-       if (__probable(!(uthread->uu_flag & UT_VFORK)))
+       if (__probable(!(uthread->uu_flag & UT_VFORK))) {
                p = (struct proc *)get_bsdtask_info(current_task());
-       else 
+       } else {
                p = current_proc();
+       }
 
        /* Verify that we are not being called from a task without a proc */
        if (__improbable(p == NULL)) {
@@ -301,21 +328,23 @@ unix_syscall64(x86_saved_state_t *state)
                /* NOTREACHED */
        }
 
-       code = regs->rax & SYSCALL_NUMBER_MASK;
+       code    = regs->rax & SYSCALL_NUMBER_MASK;
+       syscode = (code < nsysent) ? code : SYS_invalid;
        DEBUG_KPRINT_SYSCALL_UNIX(
                "unix_syscall64: code=%d(%s) rip=%llx\n",
-               code, syscallnames[code >= nsysent ? SYS_invalid : code], regs->isf.rip);
-       callp = (code >= nsysent) ? &sysent[SYS_invalid] : &sysent[code];
+               code, syscallnames[syscode], regs->isf.rip);
+       callp = &sysent[syscode];
 
        vt = (void *)uthread->uu_arg;
 
        if (__improbable(callp == sysent)) {
-               /*
+               /*
                 * indirect system call... system call number
                 * passed as 'arg0'
                 */
-               code = regs->rdi;
-               callp = (code >= nsysent) ? &sysent[SYS_invalid] : &sysent[code];
+               code    = regs->rdi;
+               syscode = (code < nsysent) ? code : SYS_invalid;
+               callp   = &sysent[syscode];
                args_start_at_rdi = FALSE;
                args_in_regs = 5;
        } else {
@@ -329,13 +358,11 @@ unix_syscall64(x86_saved_state_t *state)
                args_in_regs = MIN(args_in_regs, callp->sy_narg);
                memcpy(vt, args_start_at_rdi ? &regs->rdi : &regs->rsi, args_in_regs * sizeof(syscall_arg_t));
 
-
                if (!code_is_kdebug_trace(code)) {
-                       uint64_t *ip = (uint64_t *)vt;
+                       uint64_t *uip = vt;
 
-                       KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
-                               BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_START,
-                               (int)(*ip), (int)(*(ip+1)), (int)(*(ip+2)), (int)(*(ip+3)), 0);
+                       KDBG_RELEASE(BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_START,
+                           uip[0], uip[1], uip[2], uip[3]);
                }
 
                if (__improbable(callp->sy_narg > args_in_regs)) {
@@ -351,10 +378,9 @@ unix_syscall64(x86_saved_state_t *state)
                                /* NOTREACHED */
                        }
                }
-       } else
-               KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
-                       BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_START,
-                       0, 0, 0, 0, 0);
+       } else {
+               KDBG_RELEASE(BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_START);
+       }
 
        /*
         * Delayed binding of thread credential to process credential, if we
@@ -366,25 +392,40 @@ unix_syscall64(x86_saved_state_t *state)
        uthread->uu_rval[1] = 0;
        uthread->uu_flag |= UT_NOTCANCELPT;
        uthread->syscall_code = code;
+       pid = proc_pid(p);
 
 #ifdef JOE_DEBUG
-        uthread->uu_iocount = 0;
-        uthread->uu_vpindex = 0;
+       uthread->uu_iocount = 0;
+       uthread->uu_vpindex = 0;
 #endif
 
+#if CONFIG_MACF
+       if (__improbable(p->syscall_filter_mask != NULL && !bitstr_test(p->syscall_filter_mask, syscode))) {
+               error = mac_proc_check_syscall_unix(p, syscode);
+               if (error) {
+                       goto skip_syscall;
+               }
+       }
+#endif /* CONFIG_MACF */
+
        AUDIT_SYSCALL_ENTER(code, p, uthread);
        error = (*(callp->sy_call))((void *) p, vt, &(uthread->uu_rval[0]));
        AUDIT_SYSCALL_EXIT(code, p, uthread, error);
 
+#if CONFIG_MACF
+skip_syscall:
+#endif /* CONFIG_MACF */
+
 #ifdef JOE_DEBUG
-        if (uthread->uu_iocount)
-               printf("system call returned with uu_iocount != 0\n");
+       if (uthread->uu_iocount) {
+               printf("system call returned with uu_iocount != 0\n");
+       }
 #endif
 
 #if CONFIG_DTRACE
        uthread->t_dtrace_errno = error;
 #endif /* CONFIG_DTRACE */
-       
+
        if (__improbable(error == ERESTART)) {
                /*
                 * all system calls come through via the syscall instruction
@@ -392,13 +433,11 @@ unix_syscall64(x86_saved_state_t *state)
                 * move the user's pc back to repeat the syscall:
                 */
                pal_syscall_restart( thread, state );
-       }
-       else if (error != EJUSTRETURN) {
+       } else if (error != EJUSTRETURN) {
                if (__improbable(error)) {
                        regs->rax = error;
-                       regs->isf.rflags |= EFL_CF;     /* carry bit */
+                       regs->isf.rflags |= EFL_CF;     /* carry bit */
                } else { /* (not error) */
-
                        switch (callp->sy_return_type) {
                        case _SYSCALL_RET_INT_T:
                                regs->rax = uthread->uu_rval[0];
@@ -413,7 +452,7 @@ unix_syscall64(x86_saved_state_t *state)
                        case _SYSCALL_RET_SIZE_T:
                        case _SYSCALL_RET_SSIZE_T:
                        case _SYSCALL_RET_UINT64_T:
-                               regs->rax = *((uint64_t *)(&uthread->uu_rval[0]));
+                               regs->rax = *((uint64_t *)(&uthread->uu_rval[0]));
                                regs->rdx = 0;
                                break;
                        case _SYSCALL_RET_NONE:
@@ -423,17 +462,24 @@ unix_syscall64(x86_saved_state_t *state)
                                break;
                        }
                        regs->isf.rflags &= ~EFL_CF;
-               } 
+               }
        }
 
        DEBUG_KPRINT_SYSCALL_UNIX(
                "unix_syscall64: error=%d retval=(%llu,%llu)\n",
                error, regs->rax, regs->rdx);
-       
+
        uthread->uu_flag &= ~UT_NOTCANCELPT;
+       uthread->syscall_code = 0;
+
+#if DEBUG || DEVELOPMENT
+       kern_allocation_name_t
+       prior __assert_only = thread_set_allocation_name(NULL);
+       assertf(prior == NULL, "thread_set_allocation_name(\"%s\") not cleared", kern_allocation_get_name(prior));
+#endif /* DEBUG || DEVELOPMENT */
 
        if (__improbable(uthread->uu_lowpri_window)) {
-               /*
+               /*
                 * task is marked as a low priority I/O type
                 * and the I/O we issued while in this system call
                 * collided with normal I/O operations... we'll
@@ -442,10 +488,10 @@ unix_syscall64(x86_saved_state_t *state)
                 */
                throttle_lowpri_io(1);
        }
-       if (__probable(!code_is_kdebug_trace(code)))
-               KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
-                       BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_END,
-                       error, uthread->uu_rval[0], uthread->uu_rval[1], p->p_pid, 0);
+       if (__probable(!code_is_kdebug_trace(code))) {
+               KDBG_RELEASE(BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_END,
+                   error, uthread->uu_rval[0], uthread->uu_rval[1], pid);
+       }
 
 #if PROC_REF_DEBUG
        if (__improbable(uthread_get_proc_refcount(uthread))) {
@@ -461,8 +507,8 @@ unix_syscall64(x86_saved_state_t *state)
 void
 unix_syscall_return(int error)
 {
-       thread_t                thread;
-       struct uthread          *uthread;
+       thread_t                thread;
+       struct uthread          *uthread;
        struct proc *p;
        unsigned int code;
        struct sysent *callp;
@@ -483,8 +529,9 @@ unix_syscall_return(int error)
                callp = (code >= nsysent) ? &sysent[SYS_invalid] : &sysent[code];
 
 #if CONFIG_DTRACE
-               if (callp->sy_call == dtrace_systrace_syscall)
+               if (callp->sy_call == dtrace_systrace_syscall) {
                        dtrace_systrace_syscall_return( code, error, uthread->uu_rval );
+               }
 #endif /* CONFIG_DTRACE */
                AUDIT_SYSCALL_EXIT(code, p, uthread, error);
 
@@ -492,14 +539,12 @@ unix_syscall_return(int error)
                        /*
                         * repeat the syscall
                         */
-                       pal_syscall_restart( thread, find_user_regs(thread) );
-               }
-               else if (error != EJUSTRETURN) {
+                       pal_syscall_restart( thread, find_user_regs(thread));
+               } else if (error != EJUSTRETURN) {
                        if (error) {
                                regs->rax = error;
-                               regs->isf.rflags |= EFL_CF;     /* carry bit */
+                               regs->isf.rflags |= EFL_CF;     /* carry bit */
                        } else { /* (not error) */
-
                                switch (callp->sy_return_type) {
                                case _SYSCALL_RET_INT_T:
                                        regs->rax = uthread->uu_rval[0];
@@ -524,13 +569,13 @@ unix_syscall_return(int error)
                                        break;
                                }
                                regs->isf.rflags &= ~EFL_CF;
-                       } 
+                       }
                }
                DEBUG_KPRINT_SYSCALL_UNIX(
                        "unix_syscall_return: error=%d retval=(%llu,%llu)\n",
                        error, regs->rax, regs->rdx);
        } else {
-               x86_saved_state32_t     *regs;
+               x86_saved_state32_t     *regs;
 
                regs = saved_state32(find_user_regs(thread));
 
@@ -540,22 +585,22 @@ unix_syscall_return(int error)
                callp = (code >= nsysent) ? &sysent[SYS_invalid] : &sysent[code];
 
 #if CONFIG_DTRACE
-               if (callp->sy_call == dtrace_systrace_syscall)
+               if (callp->sy_call == dtrace_systrace_syscall) {
                        dtrace_systrace_syscall_return( code, error, uthread->uu_rval );
+               }
 #endif /* CONFIG_DTRACE */
                AUDIT_SYSCALL_EXIT(code, p, uthread, error);
 
                if (error == ERESTART) {
-                       pal_syscall_restart( thread, find_user_regs(thread) );
-               }
-               else if (error != EJUSTRETURN) {
+                       pal_syscall_restart( thread, find_user_regs(thread));
+               } else if (error != EJUSTRETURN) {
                        if (error) {
                                regs->eax = error;
-                               regs->efl |= EFL_CF;    /* carry bit */
+                               regs->efl |= EFL_CF;    /* carry bit */
                        } else { /* (not error) */
                                regs->eax = uthread->uu_rval[0];
                                regs->edx = uthread->uu_rval[1];
-                       } 
+                       }
                }
                DEBUG_KPRINT_SYSCALL_UNIX(
                        "unix_syscall_return: error=%d retval=(%u,%u)\n",
@@ -565,8 +610,14 @@ unix_syscall_return(int error)
 
        uthread->uu_flag &= ~UT_NOTCANCELPT;
 
+#if DEBUG || DEVELOPMENT
+       kern_allocation_name_t
+       prior __assert_only = thread_set_allocation_name(NULL);
+       assertf(prior == NULL, "thread_set_allocation_name(\"%s\") not cleared", kern_allocation_get_name(prior));
+#endif /* DEBUG || DEVELOPMENT */
+
        if (uthread->uu_lowpri_window) {
-               /*
+               /*
                 * task is marked as a low priority I/O type
                 * and the I/O we issued while in this system call
                 * collided with normal I/O operations... we'll
@@ -575,10 +626,10 @@ unix_syscall_return(int error)
                 */
                throttle_lowpri_io(1);
        }
-       if (!code_is_kdebug_trace(code))
-               KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
-                       BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_END,
-                       error, uthread->uu_rval[0], uthread->uu_rval[1], p->p_pid, 0);
+       if (!code_is_kdebug_trace(code)) {
+               KDBG_RELEASE(BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_END,
+                   error, uthread->uu_rval[0], uthread->uu_rval[1], p->p_pid);
+       }
 
        thread_exception_return();
        /* NOTREACHED */