xnu-4903.241.1.tar.gz

[apple/xnu.git] / libsyscall / custom / __vfork.s

diff --git a/libsyscall/custom/__vfork.s b/libsyscall/custom/__vfork.s
index 8449d25e4091ad8217e27d1214528ff504ef44f8..65a781efd9f2d68f121e242830e2930b8dc5f819 100644 (file)
--- a/libsyscall/custom/__vfork.s
+++ b/libsyscall/custom/__vfork.s
@@ -128,6 +128,107 @@ L2:
        addl            $1, (%rdx)
        jmp             *%rdi
 
+#elif defined(__arm__)
+
+#include <arm/arch.h>
+               
+       .globl  cerror
+       MI_ENTRY_POINT(___vfork)
+
+       MI_GET_ADDRESS(r3, __current_pid)       // get address of __current_pid
+#ifdef _ARM_ARCH_6
+L0:    
+       ldrex   r1, [r3]
+       subs    r1, r1, #1                      // if __current_pid <= 0, decrement it
+       movpl   r1, #-1                         // otherwise put -1 in there
+       strex   r2, r1, [r3]
+       cmp     r2, #0
+       bne     L0
+#else
+       mov     r2, #0x80000000                 // load "looking" value
+L0:    
+       swp     r1, r2, [r3]                    // look at the value, lock others out
+       cmp     r1, r2                          // anyone else trying to look?
+       beq     L0                              // yes, so wait our turn
+        subs    r1, r1, #1                      // if __current_pid <= 0, decrement it
+       movpl   r1, #-1                         // otherwise put -1 in there
+       str     r1, [r3]
+#endif
+               
+       mov     r1, #1                                  // prime results
+       mov     r12, #SYS_vfork
+       swi     #SWI_SYSCALL                            // make the syscall
+       bcs     Lbotch                                  // error?
+       cmp     r1, #0                                  // parent (r1=0) or child(r1=1)
+       beq     Lparent
+
+       //child here...
+       mov     r0, #0
+       bx      lr                                      // return
+
+Lbotch:
+       MI_CALL_EXTERNAL(_cerror)                       // jump here on error
+       mov     r0,#-1                                  // set the error
+       // reload values clobbered by cerror (so we can treat them as live in Lparent)
+       MI_GET_ADDRESS(r3, __current_pid)               // get address of __current_pid
+#ifndef _ARM_ARCH_6
+       mov     r2, #0x80000000                 // load "looking" value
+#endif
+       // fall thru
+       
+Lparent:       
+#ifdef _ARM_ARCH_6
+       ldrex   r1, [r3]
+       add     r1, r1, #1                      // we're back, decrement vfork count
+       strex   r2, r1, [r3]
+       cmp     r2, #0
+       bne     Lparent
+#else
+       swp     r1, r2, [r3]                    // look at the value, lock others out
+       cmp     r1, r2                          // anyone else trying to look?
+       beq     Lparent                         // yes, so wait our turn
+       add     r1, r1, #1                      // we're back, decrement vfork count
+       str     r1, [r3]
+#endif
+
+       bx      lr                                      // return
+
+#elif defined(__arm64__)
+
+       MI_ENTRY_POINT(___vfork)
+
+       MI_GET_ADDRESS(x9, __current_pid)
+Ltry_set_vfork:
+       ldxr    w10, [x9]                       // Get old current pid value (exclusive)
+       mov             w11, #-1                        // Will be -1 if current value is positive
+       subs    w10, w10, #1            // Subtract one
+       csel    w12, w11, w10, pl       // If >= 0, set to -1, else set to (current - 1)
+       stxr    w13, w12, [x9]          // Attempt exclusive store to current pid
+       cbnz    w13, Ltry_set_vfork     // If store failed, retry
+       
+       // ARM sets r1 to 1 here.  I don't see why.
+       mov             w16, #SYS_vfork         // Set syscall code
+       svc             #SWI_SYSCALL
+       b.cs    Lbotch
+       cbz             w1, Lparent
+
+       // Child
+       mov             w0, #0
+       ret
+
+       // Error case
+Lbotch:
+       bl              _cerror                         // Update errno
+       mov             w0, #-1                         // Set return value
+       MI_GET_ADDRESS(x9, __current_pid) // Reload current pid address
+       // Fall through 
+Lparent:
+       ldxr    w10, [x9]                       // Exclusive load current pid value
+       add             w10, w10, #1            // Increment (i.e. decrement vfork count)
+       stxr    w11, w10, [x9]          // Attempt exclusive store of updated vfork count
+       cbnz    w11, Lparent            // If exclusive store failed, retry
+       ret                                                     // Done, return
+
 #else
 #error Unsupported architecture
 #endif