S390: Always use svc 0

On s390x syscalls are triggered by svc instruction. One can
pass the syscall number encoded in the instruction "svc 123"
or by storing it in r1:
lghi r1,123
svc 0

If the syscall number is encoded in the instruction, this can
cause broken syscall restarts.  Therefore this patch is now just
passing the syscall number in r1.

See also kernel-commit:
"s390/signal: switch to using vdso for sigreturn and syscall restart"
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/s390/[%e2%80%a6]call.c?h=v6.0-rc1&id=df29a7440c4b5c65765c8f60396b3b13063e24e9

As information, the "svc 0" feature was introduced in kernel 2.5.62:
commit b5aad611393ef2e132e3648fa4c6e56a9cfa8708

6 files changed, 22 insertions, 18 deletions

diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/clone.S b/sysdeps/unix/sysv/linux/s390/s390-32/clone.S
index 8b7d8dd..dc2d663 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/clone.S
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/clone.S
@@ -30,9 +30,10 @@
 
 	.text
 ENTRY(__clone)
-	st	%r6,24(%r15)		/* store %r6 to save area */
+	stm     %r6,%r7,24(%r15)	/* Save registers.  */
+	cfi_offset (%r7, -68)
 	cfi_offset (%r6, -72)
-	ltr     %r1,%r2			/* check fn and move to %r1 */
+	ltr     %r7,%r2			/* check fn and move to %r7 */
 	jz      error			/* no NULL function pointers */
 	lhi     %r0,-8			/* Align the child_stack to a ...  */
 	nr      %r3,%r0			/* double word boundary and ...  */
@@ -43,10 +44,11 @@ ENTRY(__clone)
 	lr	%r4,%r6			/* move parent_tid to %r4 */
 	l	%r5,100(%r15)		/* load child_tid from stack */
 	l	%r6,96(%r15)		/* load tls from stack */
-	svc	SYS_ify(clone)
+	lhi	%r1,SYS_ify(clone)
+	svc	0
 	ltr	%r2,%r2			/* check return code */
 	jz	thread_start
-	l	%r6,24(%r15)		/* restore %r6 */
+	lm	%r6,%r7,24(%r15)	/* Load registers.  */
 	jm	SYSCALL_ERROR_LABEL
 	br	%r14
 error:
@@ -58,11 +60,11 @@ thread_start:
 	cfi_startproc
 	/* Mark r14 as undefined in order to stop unwinding here!  */
 	cfi_undefined (r14)
-	/* fn is in gpr 1, arg in gpr 0 */
+	/* fn is in gpr 7, arg in gpr 0 */
 	lr      %r2,%r0         /* set first parameter to void *arg */
 	ahi     %r15,-96        /* make room on the stack for the save area */
 	xc	0(4,%r15),0(%r15)
-	basr    %r14,%r1        /* jump to fn */
+	basr    %r14,%r7        /* jump to fn */
 	DO_CALL (exit, 1)
 	cfi_endproc
 
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/getcontext.S b/sysdeps/unix/sysv/linux/s390/s390-32/getcontext.S
index 842ea28..8825caa 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/getcontext.S
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/getcontext.S
@@ -32,16 +32,18 @@
   other than the PRESERVED state.  */
 
 ENTRY(__getcontext)
-	lr      %r1,%r2
+	lr	%r0,%r2
 
 	/* rt_sigprocmask (SIG_BLOCK, NULL, &sc->sc_mask, sigsetsize).  */
+	la	%r4,SC_MASK(%r2)
 	la      %r2,SIG_BLOCK
 	slr	%r3,%r3
-	la	%r4,SC_MASK(%r1)
 	lhi	%r5,_NSIG8
-	svc	SYS_ify(rt_sigprocmask)
+	lhi	%r1,SYS_ify(rt_sigprocmask)
+	svc	0
 
 	/* Store fpu context.  */
+	lr	%r1,%r0
 	stfpc   SC_FPC(%r1)
 	std     %f0,SC_FPRS(%r1)
 	std     %f1,SC_FPRS+8(%r1)
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/setcontext.S b/sysdeps/unix/sysv/linux/s390/s390-32/setcontext.S
index 83fc2b4..14251bc 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/setcontext.S
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/setcontext.S
@@ -30,16 +30,18 @@
   other than the PRESERVED state.  */
 
 ENTRY(__setcontext)
-	lr	%r1,%r2
+	lr	%r0,%r2
 
 	/* rt_sigprocmask (SIG_SETMASK, &sc->sc_mask, NULL, sigsetsize).  */
+	la	%r3,SC_MASK(%r2)
 	la      %r2,SIG_SETMASK
-	la	%r3,SC_MASK(%r1)
 	slr	%r4,%r4
 	lhi	%r5,_NSIG8
-	svc	SYS_ify(rt_sigprocmask)
+	lhi	%r1,SYS_ify(rt_sigprocmask)
+	svc	0
 
 	/* Load fpu context.  */
+	lr	%r1,%r0
 	lfpc	SC_FPC(%r1)
 	ld	%f0,SC_FPRS(%r1)
 	ld      %f1,SC_FPRS+8(%r1)
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/swapcontext.S b/sysdeps/unix/sysv/linux/s390/s390-32/swapcontext.S
index def4e8b..b75bf75 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/swapcontext.S
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/swapcontext.S
@@ -73,7 +73,8 @@ ENTRY(__swapcontext)
 	la	%r3,SC_MASK(%r5)
 	la	%r4,SC_MASK(%r1)
 	lhi	%r5,_NSIG8
-	svc	SYS_ify(rt_sigprocmask)
+	lhi	%r1,SYS_ify(rt_sigprocmask)
+	svc	0
 
 	/* Load fpu context.  */
 	lr	%r5,%r0
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h b/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
index 967949f..e41106b 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
@@ -155,12 +155,8 @@
     lr %r0,%r7;								      \
     l %r7,96(%r15);							      \
   .endif;								      \
-  .if SYS_ify (syscall) < 256;						      \
-    svc SYS_ify (syscall);						      \
-  .else;								      \
     lhi %r1,SYS_ify (syscall);						      \
     svc 0;								      \
-  .endif;								      \
   .if args > 5;								      \
     lr %r7,%r0;								      \
   .endif
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/vfork.S b/sysdeps/unix/sysv/linux/s390/s390-32/vfork.S
index bdf8cb9..76a5570 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/vfork.S
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/vfork.S
@@ -28,7 +28,8 @@
 
 ENTRY (__libc_vfork)
 	/* Do vfork system call.  */
-	svc	SYS_ify (vfork)
+	lhi	%r1,SYS_ify (vfork)
+	svc	0
 
 	/* Check for error.  */
 	lhi	%r4,-4095