/*
* Function: unix_syscall
*
* Inputs: regs - pointer to i386 save area
*
* Outputs: none
*/
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;
assert(is_saved_state32(state));
regs = saved_state32(state);
#if DEBUG
if (regs->eax == 0x800)
thread_exception_return();
#endif
thread = current_thread();
uthread = get_bsdthread_info(thread);
/* Get the approriate proc; may be different from task's for vfork() */
is_vfork = uthread->uu_flag & UT_VFORK;
if (__improbable(is_vfork != 0))
p = current_proc();
else
p = (struct proc *)get_bsdtask_info(current_task());
/* Verify that we are not being called from a task without a proc */
if (__improbable(p == NULL)) {
regs->eax = EPERM;
regs->efl |= EFL_CF;
task_terminate_internal(current_task());
thread_exception_return();
/* NOTREACHED */
}
code = regs->eax & I386_SYSCALL_NUMBER_MASK;
DEBUG_KPRINT_SYSCALL_UNIX("unix_syscall: code=%d(%s) eip=%u\n",
code, syscallnames[code >= NUM_SYSENT ? 63 : code], (uint32_t)regs->eip);
params = (vm_offset_t) (regs->uesp + sizeof (int));
regs->efl &= ~(EFL_CF);
callp = (code >= NUM_SYSENT) ? &sysent[63] : &sysent[code];
if (__improbable(callp == sysent)) {
code = fuword(params);
params += sizeof(int);
callp = (code >= NUM_SYSENT) ? &sysent[63] : &sysent[code];
}
vt = (void *)uthread->uu_arg;
if (callp->sy_arg_bytes != 0) {
#if CONFIG_REQUIRES_U32_MUNGING
sy_munge_t *mungerp;
#else
#error U32 syscalls on x86_64 kernel requires munging
#endif
uint32_t nargs;
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) {
regs->eax = error;
regs->efl |= EFL_CF;
thread_exception_return();
/* NOTREACHED */
}
if (__probable(code != 180)) {
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);
}
#if CONFIG_REQUIRES_U32_MUNGING
mungerp = callp->sy_arg_munge32;
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);
/*
* Delayed binding of thread credential to process credential, if we
* are not running with an explicitly set thread credential.
*/
kauth_cred_uthread_update(uthread, p);
uthread->uu_rval[0] = 0;
uthread->uu_rval[1] = 0;
uthread->uu_flag |= UT_NOTCANCELPT;
uthread->syscall_code = code;
#ifdef JOE_DEBUG
uthread->uu_iocount = 0;
uthread->uu_vpindex = 0;
#endif
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);
#ifdef JOE_DEBUG
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)) {
/*
* Move the user's pc back to repeat the syscall:
* 5 bytes for a sysenter, or 2 for an int 8x.
* The SYSENTER_TF_CS covers single-stepping over a sysenter
* - see debug trap handler in idt.s/idt64.s
*/
pal_syscall_restart(thread, state);
}
else if (error != EJUSTRETURN) {
if (__improbable(error)) {
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];
}
}
DEBUG_KPRINT_SYSCALL_UNIX(
"unix_syscall: error=%d retval=(%u,%u)\n",
error, regs->eax, regs->edx);
uthread->uu_flag &= ~UT_NOTCANCELPT;
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
* delay in order to mitigate the impact of this
* task on the normal operation of the system
*/
throttle_lowpri_io(1);
}
if (__probable(code != 180))
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 (__improbable(!is_vfork && callp->sy_call == (sy_call_t *)execve && !error)) {
pal_execve_return(thread);
}
thread_exception_return();
/* NOTREACHED */
}
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;
x86_saved_state64_t *regs;
assert(is_saved_state64(state));
regs = saved_state64(state);
#if DEBUG
if (regs->rax == 0x2000800)
thread_exception_return();
#endif
thread = current_thread();
uthread = get_bsdthread_info(thread);
/* Get the approriate proc; may be different from task's for vfork() */
if (__probable(!(uthread->uu_flag & UT_VFORK)))
p = (struct proc *)get_bsdtask_info(current_task());
else
p = current_proc();
/* Verify that we are not being called from a task without a proc */
if (__improbable(p == NULL)) {
regs->rax = EPERM;
regs->isf.rflags |= EFL_CF;
task_terminate_internal(current_task());
thread_exception_return();
/* NOTREACHED */
}
code = regs->rax & SYSCALL_NUMBER_MASK;
DEBUG_KPRINT_SYSCALL_UNIX(
"unix_syscall64: code=%d(%s) rip=%llx\n",
code, syscallnames[code >= NUM_SYSENT ? 63 : code], regs->isf.rip);
callp = (code >= NUM_SYSENT) ? &sysent[63] : &sysent[code];
vt = (void *)uthread->uu_arg;
if (__improbable(callp == sysent)) {
/*
* indirect system call... system call number
* passed as 'arg0'
*/
code = regs->rdi;
callp = (code >= NUM_SYSENT) ? &sysent[63] : &sysent[code];
args_start_at_rdi = FALSE;
args_in_regs = 5;
} else {
args_start_at_rdi = TRUE;
args_in_regs = 6;
}
if (callp->sy_narg != 0) {
assert(callp->sy_narg <= 8); /* size of uu_arg */
args_in_regs = MIN(args_in_regs, callp->sy_narg);
memcpy(vt, args_start_at_rdi ? ®s->rdi : ®s->rsi, args_in_regs * sizeof(syscall_arg_t));
if (code != 180) {
uint64_t *ip = (uint64_t *)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);
}
if (__improbable(callp->sy_narg > args_in_regs)) {
int copyin_count;
copyin_count = (callp->sy_narg - args_in_regs) * sizeof(syscall_arg_t);
error = copyin((user_addr_t)(regs->isf.rsp + sizeof(user_addr_t)), (char *)&uthread->uu_arg[args_in_regs], copyin_count);
if (error) {
regs->rax = error;
regs->isf.rflags |= EFL_CF;
thread_exception_return();
/* NOTREACHED */
}
}
} else
KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
BSDDBG_CODE(DBG_BSD_EXCP_SC, code) | DBG_FUNC_START,
0, 0, 0, 0, 0);
/*
* Delayed binding of thread credential to process credential, if we
* are not running with an explicitly set thread credential.
*/
kauth_cred_uthread_update(uthread, p);
uthread->uu_rval[0] = 0;
uthread->uu_rval[1] = 0;
uthread->uu_flag |= UT_NOTCANCELPT;
uthread->syscall_code = code;
#ifdef JOE_DEBUG
uthread->uu_iocount = 0;
uthread->uu_vpindex = 0;
#endif
AUDIT_SYSCALL_ENTER(code, p, uthread);
error = (*(callp->sy_call))((void *) p, vt, &(uthread->uu_rval[0]));
AUDIT_SYSCALL_EXIT(code, p, uthread, error);
#ifdef JOE_DEBUG
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
* in 64 bit mode... its 2 bytes in length
* move the user's pc back to repeat the syscall:
*/
pal_syscall_restart( thread, state );
}
else if (error != EJUSTRETURN) {
if (__improbable(error)) {
regs->rax = error;
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];
regs->rdx = uthread->uu_rval[1];
break;
case _SYSCALL_RET_UINT_T:
regs->rax = ((u_int)uthread->uu_rval[0]);
regs->rdx = ((u_int)uthread->uu_rval[1]);
break;
case _SYSCALL_RET_OFF_T:
case _SYSCALL_RET_ADDR_T:
case _SYSCALL_RET_SIZE_T:
case _SYSCALL_RET_SSIZE_T:
case _SYSCALL_RET_UINT64_T:
regs->rax = *((uint64_t *)(&uthread->uu_rval[0]));
regs->rdx = 0;
break;
case _SYSCALL_RET_NONE:
break;
default:
panic("unix_syscall: unknown return type");
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;
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
* delay in order to mitigate the impact of this
* task on the normal operation of the system
*/
throttle_lowpri_io(1);
}
if (__probable(code != 180))
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);
thread_exception_return();
/* NOTREACHED */
}
kern_return_t
task_name_for_pid(
struct task_name_for_pid_args *args)
{
mach_port_name_t target_tport = args->target_tport;
int pid = args->pid;
user_addr_t task_addr = args->t;
struct uthread *uthread;
proc_t p = PROC_NULL;
task_t t1;
mach_port_name_t tret;
void * sright;
int error = 0, refheld = 0;
kauth_cred_t target_cred;
AUDIT_MACH_SYSCALL_ENTER(AUE_TASKNAMEFORPID);
AUDIT_ARG(pid, pid);
AUDIT_ARG(mach_port1, target_tport);
t1 = port_name_to_task(target_tport);
if (t1 == TASK_NULL) {
(void) copyout((char *)&t1, task_addr, sizeof(mach_port_name_t));
AUDIT_MACH_SYSCALL_EXIT(KERN_FAILURE);
return(KERN_FAILURE);
}
/*
* Delayed binding of thread credential to process credential, if we
* are not running with an explicitly set thread credential.
*/
uthread = get_bsdthread_info(current_thread());
kauth_cred_uthread_update(uthread, current_proc());
p = proc_find(pid);
AUDIT_ARG(process, p);
if (p != PROC_NULL) {
target_cred = kauth_cred_proc_ref(p);
refheld = 1;
if ((p->p_stat != SZOMB)
&& ((current_proc() == p)
|| kauth_cred_issuser(kauth_cred_get())
|| ((kauth_cred_getuid(target_cred) == kauth_cred_getuid(kauth_cred_get())) &&
((target_cred->cr_ruid == kauth_cred_get()->cr_ruid))))) {
if (p->task != TASK_NULL) {
task_reference(p->task);
#if CONFIG_MACF
error = mac_proc_check_get_task_name(kauth_cred_get(), p);
if (error) {
task_deallocate(p->task);
goto noperm;
}
#endif
sright = (void *)convert_task_name_to_port(p->task);
tret = ipc_port_copyout_send(sright,
get_task_ipcspace(current_task()));
} else
tret = MACH_PORT_NULL;
AUDIT_ARG(mach_port2, tret);
(void) copyout((char *)&tret, task_addr, sizeof(mach_port_name_t));
task_deallocate(t1);
error = KERN_SUCCESS;
goto tnfpout;
}
}
#if CONFIG_MACF
noperm:
#endif
task_deallocate(t1);
tret = MACH_PORT_NULL;
(void) copyout((char *) &tret, task_addr, sizeof(mach_port_name_t));
error = KERN_FAILURE;
tnfpout:
if (refheld != 0)
kauth_cred_unref(&target_cred);
if (p != PROC_NULL)
proc_rele(p);
AUDIT_MACH_SYSCALL_EXIT(error);
return(error);
}
/*
* Routine: task_for_pid
* Purpose:
* Get the task port for another "process", named by its
* process ID on the same host as "target_task".
*
* Only permitted to privileged processes, or processes
* with the same user ID.
*
* XXX This should be a BSD system call, not a Mach trap!!!
*/
kern_return_t
task_for_pid(
struct task_for_pid_args *args)
{
mach_port_name_t target_tport = args->target_tport;
int pid = args->pid;
user_addr_t task_addr = args->t;
struct uthread *uthread;
proc_t p = PROC_NULL;
task_t t1 = TASK_NULL;
mach_port_name_t tret = MACH_PORT_NULL;
ipc_port_t tfpport;
void * sright;
int error = 0;
AUDIT_MACH_SYSCALL_ENTER(AUE_TASKFORPID);
AUDIT_ARG(pid, pid);
AUDIT_ARG(mach_port1, target_tport);
#if defined(SECURE_KERNEL)
if (0 == pid) {
(void ) copyout((char *)&t1, task_addr, sizeof(mach_port_name_t));
AUDIT_MACH_SYSCALL_EXIT(KERN_FAILURE);
return(KERN_FAILURE);
}
#endif
t1 = port_name_to_task(target_tport);
if (t1 == TASK_NULL) {
(void) copyout((char *)&t1, task_addr, sizeof(mach_port_name_t));
AUDIT_MACH_SYSCALL_EXIT(KERN_FAILURE);
return(KERN_FAILURE);
}
/*
* Delayed binding of thread credential to process credential, if we
* are not running with an explicitly set thread credential.
*/
uthread = get_bsdthread_info(current_thread());
kauth_cred_uthread_update(uthread, current_proc());
p = proc_find(pid);
AUDIT_ARG(process, p);
if (!(task_for_pid_posix_check(p))) {
error = KERN_FAILURE;
goto tfpout;
}
if (p->task != TASK_NULL) {
/* If we aren't root and target's task access port is set... */
if (!kauth_cred_issuser(kauth_cred_get()) &&
p != current_proc() &&
(task_get_task_access_port(p->task, &tfpport) == 0) &&
(tfpport != IPC_PORT_NULL)) {
if (tfpport == IPC_PORT_DEAD) {
error = KERN_PROTECTION_FAILURE;
goto tfpout;
}
/* Call up to the task access server */
error = check_task_access(tfpport, proc_selfpid(), kauth_getgid(), pid);
if (error != MACH_MSG_SUCCESS) {
if (error == MACH_RCV_INTERRUPTED)
error = KERN_ABORTED;
else
error = KERN_FAILURE;
goto tfpout;
}
}
#if CONFIG_MACF
error = mac_proc_check_get_task(kauth_cred_get(), p);
if (error) {
error = KERN_FAILURE;
goto tfpout;
}
#endif
/* Grant task port access */
task_reference(p->task);
sright = (void *) convert_task_to_port(p->task);
tret = ipc_port_copyout_send(
sright,
get_task_ipcspace(current_task()));
}
error = KERN_SUCCESS;
tfpout:
task_deallocate(t1);
AUDIT_ARG(mach_port2, tret);
(void) copyout((char *) &tret, task_addr, sizeof(mach_port_name_t));
if (p != PROC_NULL)
proc_rele(p);
AUDIT_MACH_SYSCALL_EXIT(error);
return(error);
}
kern_return_t
dtrace_user_probe(arm_saved_state_t *regs, unsigned int instr)
{
/*
* FIXME
*
* The only call path into this method is always a user trap.
* We don't need to test for user trap, but should assert it.
*/
lck_rw_t *rwp;
struct proc *p = current_proc();
uthread_t uthread = (uthread_t)get_bsdthread_info(current_thread());
kauth_cred_uthread_update(uthread, p);
if (((regs->cpsr & PSR_TF) && ((uint16_t) instr) == FASTTRAP_THUMB_RET_INSTR) ||
((uint32_t) instr == FASTTRAP_ARM_RET_INSTR)) {
uint8_t step = uthread->t_dtrace_step;
uint8_t ret = uthread->t_dtrace_ret;
user_addr_t npc = uthread->t_dtrace_npc;
if (uthread->t_dtrace_ast) {
printf("dtrace_user_probe() should be calling aston()\n");
// aston(thread);
// uthread->t_sig_check = 1;
}
/*
* Clear all user tracing flags.
*/
uthread->t_dtrace_ft = 0;
/*
* If we weren't expecting to take a return probe trap, kill
* the process as though it had just executed an unassigned
* trap instruction.
*/
if (step == 0) {
/*
* APPLE NOTE: We're returning KERN_FAILURE, which causes
* the generic signal handling code to take over, which will effectively
* deliver a EXC_BAD_INSTRUCTION to the user process.
*/
return KERN_FAILURE;
}
/*
* If we hit this trap unrelated to a return probe, we're
* just here to reset the AST flag since we deferred a signal
* until after we logically single-stepped the instruction we
* copied out.
*/
if (ret == 0) {
regs->pc = npc;
return KERN_SUCCESS;
}
/*
* We need to wait until after we've called the
* dtrace_return_probe_ptr function pointer to step the pc.
*/
rwp = &CPU->cpu_ft_lock;
lck_rw_lock_shared(rwp);
if (dtrace_return_probe_ptr != NULL)
(void) (*dtrace_return_probe_ptr)(regs);
lck_rw_unlock_shared(rwp);
regs->pc = npc;
return KERN_SUCCESS;
} else {
rwp = &CPU->cpu_ft_lock;
/*
* The DTrace fasttrap provider uses a trap,
* FASTTRAP_{ARM,THUMB}_INSTR. We let
* DTrace take the first crack at handling
* this trap; if it's not a probe that DTrace knows about,
* we call into the trap() routine to handle it like a
* breakpoint placed by a conventional debugger.
*/
/*
* APPLE NOTE: I believe the purpose of the reader/writers lock
* is thus: There are times which dtrace needs to prevent calling
* dtrace_pid_probe_ptr(). Sun's original impl grabbed a plain
* mutex here. However, that serialized all probe calls, and
* destroyed MP behavior. So now they use a RW lock, with probes
* as readers, and the top level synchronization as a writer.
*/
lck_rw_lock_shared(rwp);
if (dtrace_pid_probe_ptr != NULL &&
(*dtrace_pid_probe_ptr)(regs) == 0) {
lck_rw_unlock_shared(rwp);
return KERN_SUCCESS;
}
lck_rw_unlock_shared(rwp);
/*
* If the instruction that caused the breakpoint trap doesn't
* look like our trap anymore, it may be that this tracepoint
* was removed just after the user thread executed it. In
* that case, return to user land to retry the instuction.
*
* Note that the PC points to the instruction that caused the fault.
*/
if (regs->cpsr & PSR_TF) {
uint16_t instr_check;
if (fuword16(regs->pc, &instr_check) == 0 && instr_check != FASTTRAP_THUMB_INSTR) {
return KERN_SUCCESS;
}
} else {
uint32_t instr_check;
if (fuword32(regs->pc, &instr_check) == 0 && instr_check != FASTTRAP_ARM_INSTR) {
return KERN_SUCCESS;
}
}
}
return KERN_FAILURE;
}
kern_return_t
dtrace_user_probe(x86_saved_state_t *regs)
{
x86_saved_state64_t *regs64;
x86_saved_state32_t *regs32;
int trapno;
/*
* FIXME!
*
* The only call path into this method is always a user trap.
* We don't need to test for user trap, but should assert it.
*/
boolean_t user_mode = TRUE;
if (is_saved_state64(regs) == TRUE) {
regs64 = saved_state64(regs);
regs32 = NULL;
trapno = regs64->isf.trapno;
user_mode = TRUE; // By default, because xnu is 32 bit only
} else {
regs64 = NULL;
regs32 = saved_state32(regs);
if (regs32->cs & 0x03) user_mode = TRUE;
trapno = regs32->trapno;
}
lck_rw_t *rwp;
struct proc *p = current_proc();
uthread_t uthread = (uthread_t)get_bsdthread_info(current_thread());
if (user_mode /*|| (rp->r_ps & PS_VM)*/) {
/*
* DTrace accesses t_cred in probe context. t_cred
* must always be either NULL, or point to a valid,
* allocated cred structure.
*/
kauth_cred_uthread_update(uthread, p);
}
if (trapno == T_DTRACE_RET) {
uint8_t step = uthread->t_dtrace_step;
uint8_t ret = uthread->t_dtrace_ret;
user_addr_t npc = uthread->t_dtrace_npc;
if (uthread->t_dtrace_ast) {
printf("dtrace_user_probe() should be calling aston()\n");
// aston(uthread);
// uthread->t_sig_check = 1;
}
/*
* Clear all user tracing flags.
*/
uthread->t_dtrace_ft = 0;
/*
* If we weren't expecting to take a return probe trap, kill
* the process as though it had just executed an unassigned
* trap instruction.
*/
if (step == 0) {
/*
* APPLE NOTE: We're returning KERN_FAILURE, which causes
* the generic signal handling code to take over, which will effectively
* deliver a EXC_BAD_INSTRUCTION to the user process.
*/
return KERN_FAILURE;
}
/*
* If we hit this trap unrelated to a return probe, we're
* just here to reset the AST flag since we deferred a signal
* until after we logically single-stepped the instruction we
* copied out.
*/
if (ret == 0) {
if (regs64) {
regs64->isf.rip = npc;
} else {
regs32->eip = npc;
}
return KERN_SUCCESS;
}
/*
* We need to wait until after we've called the
* dtrace_return_probe_ptr function pointer to set %pc.
*/
rwp = &CPU->cpu_ft_lock;
lck_rw_lock_shared(rwp);
if (dtrace_return_probe_ptr != NULL)
(void) (*dtrace_return_probe_ptr)(regs);
lck_rw_unlock_shared(rwp);
if (regs64) {
regs64->isf.rip = npc;
} else {
regs32->eip = npc;
}
return KERN_SUCCESS;
} else if (trapno == T_INT3) {
uint8_t instr;
rwp = &CPU->cpu_ft_lock;
/*
* The DTrace fasttrap provider uses the breakpoint trap
* (int 3). We let DTrace take the first crack at handling
* this trap; if it's not a probe that DTrace knowns about,
* we call into the trap() routine to handle it like a
* breakpoint placed by a conventional debugger.
*/
/*
* APPLE NOTE: I believe the purpose of the reader/writers lock
* is thus: There are times which dtrace needs to prevent calling
* dtrace_pid_probe_ptr(). Sun's original impl grabbed a plain
* mutex here. However, that serialized all probe calls, and
* destroyed MP behavior. So now they use a RW lock, with probes
* as readers, and the top level synchronization as a writer.
*/
lck_rw_lock_shared(rwp);
if (dtrace_pid_probe_ptr != NULL &&
(*dtrace_pid_probe_ptr)(regs) == 0) {
lck_rw_unlock_shared(rwp);
return KERN_SUCCESS;
}
lck_rw_unlock_shared(rwp);
/*
* If the instruction that caused the breakpoint trap doesn't
* look like an int 3 anymore, it may be that this tracepoint
* was removed just after the user thread executed it. In
* that case, return to user land to retry the instuction.
*/
user_addr_t pc = (regs64) ? regs64->isf.rip : (user_addr_t)regs32->eip;
if (fuword8(pc - 1, &instr) == 0 && instr != FASTTRAP_INSTR) {
if (regs64) {
regs64->isf.rip--;
} else {
regs32->eip--;
}
return KERN_SUCCESS;
}
}
return KERN_FAILURE;
}