Bug 18125: Call exit after last linked context.

There appears to be a discrepancy among the implementations
of setcontext with regards to the function called once the last
linked-to context has finished executing via setcontext.

The POSIX standard says:
~~~
If the uc_link member of the ucontext_t structure pointed to by
the ucp argument is equal to 0, then this context is the main
context, and the thread will exit when this context returns.
~~~

It says "exit" not "exit immediately" nor "exit without running
functions registered with atexit or on_exit."

Therefore the AArch64, ARM, hppa and NIOS II implementations are
wrong and no test detects it.

It is questionable if this should even be fixed or just documented
that the above 4 targets are wrong. The functions are deprecated
and nobody should be using them, but at the same time it silly to
have cross-target differences that make it hard to port old
applications from say x86_64 to AArch64.

Therefore I will ix the 4 arches, and checkin a regression
test to prevent it from changing again.

https://sourceware.org/ml/libc-alpha/2015-03/msg00720.html

4 files changed, 7 insertions, 6 deletions

diff --git a/sysdeps/unix/sysv/linux/aarch64/setcontext.S b/sysdeps/unix/sysv/linux/aarch64/setcontext.S
index 6dd78361cd..ae67581660 100644
--- a/sysdeps/unix/sysv/linux/aarch64/setcontext.S
+++ b/sysdeps/unix/sysv/linux/aarch64/setcontext.S
@@ -125,5 +125,5 @@ weak_alias (__setcontext, setcontext)
 ENTRY (__startcontext)
 	mov	x0, x19
 	cbnz	x0, __setcontext
-1:	b       HIDDEN_JUMPTARGET (_exit)
+1:	b       HIDDEN_JUMPTARGET (exit)
 END (__startcontext)
diff --git a/sysdeps/unix/sysv/linux/arm/setcontext.S b/sysdeps/unix/sysv/linux/arm/setcontext.S
index 5268e06892..24c72945c8 100644
--- a/sysdeps/unix/sysv/linux/arm/setcontext.S
+++ b/sysdeps/unix/sysv/linux/arm/setcontext.S
@@ -91,7 +91,7 @@ ENTRY(__startcontext)
 	bne     PLTJMP(__setcontext)
 
 	@ New context was 0 - exit
-	b       PLTJMP(HIDDEN_JUMPTARGET(_exit))
+	b       PLTJMP(HIDDEN_JUMPTARGET(exit))
 END(__startcontext)
 
 #ifdef PIC
diff --git a/sysdeps/unix/sysv/linux/hppa/setcontext.S b/sysdeps/unix/sysv/linux/hppa/setcontext.S
index 72714104f8..abe87a9603 100644
--- a/sysdeps/unix/sysv/linux/hppa/setcontext.S
+++ b/sysdeps/unix/sysv/linux/hppa/setcontext.S
@@ -18,6 +18,7 @@
    <http://www.gnu.org/licenses/>.  */
 
 #include <sysdep.h>
+#include <libc-symbols.h>
 
 #include "ucontext_i.h"
 
@@ -139,7 +140,7 @@ ENTRY(__setcontext)
 	nop
 
 	/* No further context available. Exit now.  */
-	bl	_exit, %r2
+	bl	HIDDEN_JUMPTARGET(exit), %r2
 	ldi	-1, %r26
 
 
diff --git a/sysdeps/unix/sysv/linux/nios2/setcontext.S b/sysdeps/unix/sysv/linux/nios2/setcontext.S
index 9a8dd87b93..f40b73389d 100644
--- a/sysdeps/unix/sysv/linux/nios2/setcontext.S
+++ b/sysdeps/unix/sysv/linux/nios2/setcontext.S
@@ -89,15 +89,15 @@ ENTRY(__startcontext)
 	mov	r4, r16
 	bne	r4, zero, __setcontext
 
-	/* If uc_link == zero, call _exit.  */
+	/* If uc_link == zero, call exit.  */
 #ifdef PIC
 	nextpc	r22
 1:	movhi	r8, %hiadj(_gp_got - 1b)
 	addi	r8, r8, %lo(_gp_got - 1b)
 	add	r22, r22, r8
-	ldw	r8, %call(HIDDEN_JUMPTARGET(_exit))(r22)
+	ldw	r8, %call(HIDDEN_JUMPTARGET(exit))(r22)
 	jmp	r8
 #else
-	jmpi	_exit
+	jmpi	exit
 #endif
 END(__startcontext)