prepare cancellation syscall asm for possibility of __cancel returning

src/thread/arm/syscall_cp.s

@@ -7,7 +7,7 @@ __syscall_cp_asm:
 __cp_begin:
 	ldr r0,[r0]
 	cmp r0,#0
-	blne __cancel
+	blne __cp_cancel
 	mov r7,r1
 	mov r0,r2
 	mov r1,r3
@@ -19,3 +19,7 @@ __cp_end:
 	tst lr,#1
 	moveq pc,lr
 	bx lr
+.global __cp_cancel
+__cp_cancel:
+	ldmfd sp!,{r4,r5,r6,r7,lr}
+	b __cancel

src/thread/i386/syscall_cp.s

@@ -11,7 +11,7 @@ __syscall_cp_asm:
 __cp_begin:
 	movl (%ecx),%eax
 	testl %eax,%eax
-	jnz __cancel
+	jnz __cp_cancel
 	movl 24(%esp),%eax
 	movl 28(%esp),%ebx
 	movl 32(%esp),%ecx
@@ -27,3 +27,10 @@ __cp_end:
 	popl %esi
 	popl %ebx
 	ret
+.global __cp_cancel
+__cp_cancel:
+	popl %ebp
+	popl %edi
+	popl %esi
+	popl %ebx
+	jmp __cancel

src/thread/mips/syscall_cp.s

@@ -3,19 +3,19 @@
 .global __syscall_cp_asm
 .type   __syscall_cp_asm,@function
 __syscall_cp_asm:
+	subu    $sp, $sp, 32
 .global __cp_begin
 __cp_begin:
 	lw      $4, 0($4)
-	bne     $4, $0, 2f
+	bne     $4, $0, __cp_cancel
 	move    $2, $5
 	move    $4, $6
 	move    $5, $7
-	lw      $6, 16($sp)
-	lw      $7, 20($sp)
-	lw      $8, 24($sp)
-	lw      $9, 28($sp)
-	lw      $10,32($sp)
-	subu    $sp, $sp, 32
+	lw      $6, 48($sp)
+	lw      $7, 52($sp)
+	lw      $8, 56($sp)
+	lw      $9, 60($sp)
+	lw      $10,64($sp)
 	sw      $8, 16($sp)
 	sw      $9, 20($sp)
 	sw      $10,24($sp)
@@ -29,6 +29,10 @@ __cp_end:
 	subu    $2, $0, $2
 1:	jr      $ra
 	nop
-2:	lw      $25, %call16(__cancel)($gp)
+
+.global __cp_cancel
+__cp_cancel:
+	addu    $sp, $sp, 32
+	lw      $25, %call16(__cancel)($gp)
 	jr      $25
 	nop

src/thread/powerpc/syscall_cp.s

@@ -31,7 +31,6 @@ __cp_begin:
 	beq+ cr7, 1f #jump to label 1 if r0 was 0
 	
 	b __cancel #else call cancel 
-	# (the return address is not needed, since __cancel never returns)
 1:
 	#ok, the cancel flag was not set
 	# syscall: number goes to r0, the rest 3-8

src/thread/pthread_cancel.c

@@ -1,11 +1,18 @@
 #include "pthread_impl.h"
 #include "syscall.h"
+#include "libc.h"
 
 void __cancel()
 {
 	pthread_exit(PTHREAD_CANCELED);
 }
 
+/* If __syscall_cp_asm has adjusted the stack pointer, it must provide a
+ * definition of __cp_cancel to undo those adjustments and call __cancel.
+ * Otherwise, __cancel provides a definition for __cp_cancel. */
+
+weak_alias(__cancel, __cp_cancel);
+
 long __syscall_cp_asm(volatile void *, syscall_arg_t,
                       syscall_arg_t, syscall_arg_t, syscall_arg_t,
                       syscall_arg_t, syscall_arg_t, syscall_arg_t);