sparc: Fix restartable syscalls (BZ 32173)

The commit 'sparc: Use Linux kABI for syscall return'
(86c5d2cf0ce046279baddc7faa27da71f1a89fde) did not take into account
a subtle sparc syscall kABI constraint.  For syscalls that might block
indefinitely, on an interrupt (like SIGCONT) the kernel will set the
instruction pointer to just before the syscall:

arch/sparc/kernel/signal_64.c
476 static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
477 {
[...]
525                 if (restart_syscall) {
526                         switch (regs->u_regs[UREG_I0]) {
527                         case ERESTARTNOHAND:
528                         case ERESTARTSYS:
529                         case ERESTARTNOINTR:
530                                 /* replay the system call when we are done */
531                                 regs->u_regs[UREG_I0] = orig_i0;
532                                 regs->tpc -= 4;
533                                 regs->tnpc -= 4;
534                                 pt_regs_clear_syscall(regs);
535                                 fallthrough;
536                         case ERESTART_RESTARTBLOCK:
537                                 regs->u_regs[UREG_G1] = __NR_restart_syscall;
538                                 regs->tpc -= 4;
539                                 regs->tnpc -= 4;
540                                 pt_regs_clear_syscall(regs);
541                         }

However, on a SIGCONT it seems that 'g1' register is being clobbered after the
syscall returns.  Before 86c5d2cf0ce046279, the 'g1' was always placed jus
before the 'ta' instruction which then reloads the syscall number and restarts
the syscall.

On master, where 'g1' might be placed before 'ta':

  $ cat test.c
  #include <unistd.h>

  int main ()
  {
    pause ();
  }
  $ gcc test.c -o test
  $ strace -f ./t
  [...]
  ppoll(NULL, 0, NULL, NULL, 0

On another terminal

  $ kill -STOP 2262828

  $ strace -f ./t
  [...]
  --- SIGSTOP {si_signo=SIGSTOP, si_code=SI_USER, si_pid=2521813, si_uid=8289} ---
  --- stopped by SIGSTOP ---

And then

  $ kill -CONT 2262828

Results in:

  --- SIGCONT {si_signo=SIGCONT, si_code=SI_USER, si_pid=2521813, si_uid=8289} ---
  restart_syscall(<... resuming interrupted ppoll ...>) = -1 EINTR (Interrupted system call)

Where the expected behaviour would be:

  $ strace -f ./t
  [...]
  ppoll(NULL, 0, NULL, NULL, 0)           = ? ERESTARTNOHAND (To be restarted if no handler)
  --- SIGSTOP {si_signo=SIGSTOP, si_code=SI_USER, si_pid=2521813, si_uid=8289} ---
  --- stopped by SIGSTOP ---
  --- SIGCONT {si_signo=SIGCONT, si_code=SI_USER, si_pid=2521813, si_uid=8289} ---
  ppoll(NULL, 0, NULL, NULL, 0

Just moving the 'g1' setting near the syscall asm is not suffice,
the compiler might optimize it away (as I saw on cancellation.c by
trying this fix).  Instead, I have change the inline asm to put the
'g1' setup in ithe asm block.  This would require to change the asm
constraint for INTERNAL_SYSCALL_NCS, since the syscall number is not
constant.

Checked on sparc64-linux-gnu.

Reported-by: René Rebe <rene@exactcode.de>
Tested-by: Sam James <sam@gentoo.org>
Reviewed-by: Sam James <sam@gentoo.org>

5 files changed, 52 insertions, 36 deletions

diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/syscall_cancel.S b/sysdeps/unix/sysv/linux/sparc/sparc32/syscall_cancel.S
index 0db93c7..45c6ae7 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/syscall_cancel.S
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/syscall_cancel.S
@@ -48,13 +48,13 @@ __syscall_cancel_arch_start:
 	bne	2f
 #endif
 	/* Issue a 6 argument syscall.  */
-	 mov	%i1, %g1
-	mov	%i2, %o0
+	 mov	%i2, %o0
 	mov	%i3, %o1
 	mov	%i4, %o2
 	mov	%i5, %o3
 	ld	[%fp+92], %o4
 	ld	[%fp+96], %o5
+	 mov	%i1, %g1
 	ta	0x10
 
 	.globl __syscall_cancel_arch_end
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/sysdep.h b/sysdeps/unix/sysv/linux/sparc/sparc32/sysdep.h
index d2d68f5..c2ffbb5 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/sysdep.h
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/sysdep.h
@@ -107,6 +107,7 @@ ENTRY(name);					\
 #else  /* __ASSEMBLER__ */
 
 #define __SYSCALL_STRING						\
+	"mov	%[scn], %%g1;"						\
 	"ta	0x10;"							\
 	"bcc	1f;"							\
 	" nop;"								\
@@ -114,7 +115,7 @@ ENTRY(name);					\
 	"1:"
 
 #define __SYSCALL_CLOBBERS						\
-	"f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7",			\
+	"g1", "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7",		\
 	"f8", "f9", "f10", "f11", "f12", "f13", "f14", "f15",		\
 	"f16", "f17", "f18", "f19", "f20", "f21", "f22", "f23",		\
 	"f24", "f25", "f26", "f27", "f28", "f29", "f30", "f31",		\
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/syscall_cancel.S b/sysdeps/unix/sysv/linux/sparc/sparc64/syscall_cancel.S
index 21b0728..6c8d133 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/syscall_cancel.S
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/syscall_cancel.S
@@ -46,13 +46,13 @@ __syscall_cancel_arch_start:
 	andcc	%g2, TCB_CANCELED_BITMASK, %g0
 	bne,pn	%xcc, 2f
 	/* Issue a 6 argument syscall.  */
-	 mov	%i1, %g1
-	mov	%i2, %o0
+	 mov	%i2, %o0
 	mov	%i3, %o1
 	mov	%i4, %o2
 	mov	%i5, %o3
 	ldx	[%fp + STACK_BIAS + 176], %o4
 	ldx	[%fp + STACK_BIAS + 184], %o5
+	mov	%i1, %g1
 	ta	0x6d
 
 	.global __syscall_cancel_arch_end
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/sysdep.h b/sysdeps/unix/sysv/linux/sparc/sparc64/sysdep.h
index 9604742..5598fab 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/sysdep.h
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/sysdep.h
@@ -106,6 +106,7 @@ ENTRY(name);					\
 #else  /* __ASSEMBLER__ */
 
 #define __SYSCALL_STRING						\
+	"mov	%[scn], %%g1;"						\
 	"ta	0x6d;"							\
 	"bcc,pt	%%xcc, 1f;"						\
 	" nop;"								\
@@ -113,7 +114,7 @@ ENTRY(name);					\
 	"1:"
 
 #define __SYSCALL_CLOBBERS						\
-	"f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7",			\
+	"g1", "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7",		\
 	"f8", "f9", "f10", "f11", "f12", "f13", "f14", "f15",		\
 	"f16", "f17", "f18", "f19", "f20", "f21", "f22", "f23",		\
 	"f24", "f25", "f26", "f27", "f28", "f29", "f30", "f31",		\
diff --git a/sysdeps/unix/sysv/linux/sparc/sysdep.h b/sysdeps/unix/sysv/linux/sparc/sysdep.h
index dcabb57..c287740 100644
--- a/sysdeps/unix/sysv/linux/sparc/sysdep.h
+++ b/sysdeps/unix/sysv/linux/sparc/sysdep.h
@@ -50,97 +50,109 @@
 
 #undef INTERNAL_SYSCALL_NCS
 #define INTERNAL_SYSCALL_NCS(name, nr, args...) \
-  internal_syscall##nr(__SYSCALL_STRING, name, args)
+  _internal_syscall##nr(__SYSCALL_STRING, "p", name, args)
 
-#define internal_syscall0(string,name,dummy...)			\
+#define _internal_syscall0(string,nc,name,dummy...)	\
 ({									\
-	register long int __g1 __asm__ ("g1") = (name);			\
 	register long __o0 __asm__ ("o0");				\
+	long int _name = (long int) (name);				\
 	__asm __volatile (string : "=r" (__o0) :			\
-			  "r" (__g1) :					\
+			  [scn] nc (_name) :				\
 			  __SYSCALL_CLOBBERS);				\
 	__o0;								\
 })
+#define internal_syscall0(string,name,args...)				\
+  _internal_syscall0(string, "i", name, args)
 
-#define internal_syscall1(string,name,arg1)				\
+#define _internal_syscall1(string,nc,name,arg1)				\
 ({									\
 	long int _arg1 = (long int) (arg1);				\
-	register long int __g1 __asm__("g1") = (name);			\
+	long int _name = (long int) (name);				\
 	register long int  __o0 __asm__ ("o0") = _arg1;			\
-	__asm __volatile (string : "=r" (__o0) :			\
-			  "r" (__g1), "0" (__o0) :			\
+	__asm __volatile (string : "+r" (__o0) :			\
+			  [scn] nc (_name) :				\
 			  __SYSCALL_CLOBBERS);				\
 	__o0;								\
 })
+#define internal_syscall1(string,name,args...)				\
+  _internal_syscall1(string, "i", name, args)
 
-#define internal_syscall2(string,name,arg1,arg2)			\
+#define _internal_syscall2(string,nc,name,arg1,arg2)			\
 ({									\
 	long int _arg1 = (long int) (arg1);				\
 	long int _arg2 = (long int) (arg2);				\
-	register long int __g1 __asm__("g1") = (name);			\
+	long int _name = (long int) (name);				\
 	register long int __o0 __asm__ ("o0") = _arg1;			\
 	register long int __o1 __asm__ ("o1") = _arg2;			\
-	__asm __volatile (string : "=r" (__o0) :			\
-			  "r" (__g1), "0" (__o0), "r" (__o1) :		\
+	__asm __volatile (string : "+r" (__o0) :			\
+			  [scn] nc (_name), "r" (__o1) :		\
 			  __SYSCALL_CLOBBERS);				\
 	__o0;								\
 })
+#define internal_syscall2(string,name,args...)				\
+  _internal_syscall2(string, "i", name, args)
 
-#define internal_syscall3(string,name,arg1,arg2,arg3)			\
+#define _internal_syscall3(string,nc,name,arg1,arg2,arg3)		\
 ({									\
 	long int _arg1 = (long int) (arg1);				\
 	long int _arg2 = (long int) (arg2);				\
 	long int _arg3 = (long int) (arg3);				\
-	register long int __g1 __asm__("g1") = (name);			\
+	long int _name = (long int) (name);				\
 	register long int __o0 __asm__ ("o0") = _arg1;			\
 	register long int __o1 __asm__ ("o1") = _arg2;			\
 	register long int __o2 __asm__ ("o2") = _arg3;			\
-	__asm __volatile (string : "=r" (__o0) :			\
-			  "r" (__g1), "0" (__o0), "r" (__o1),		\
+	__asm __volatile (string : "+r" (__o0) :			\
+			  [scn] nc (_name), "r" (__o1),			\
 			  "r" (__o2) :					\
 			  __SYSCALL_CLOBBERS);				\
 	__o0;								\
 })
+#define internal_syscall3(string,name,args...)				\
+  _internal_syscall3(string, "i", name, args)
 
-#define internal_syscall4(string,name,arg1,arg2,arg3,arg4)		\
+#define _internal_syscall4(string,nc,name,arg1,arg2,arg3,arg4)		\
 ({									\
 	long int _arg1 = (long int) (arg1);				\
 	long int _arg2 = (long int) (arg2);				\
 	long int _arg3 = (long int) (arg3);				\
 	long int _arg4 = (long int) (arg4);				\
-	register long int __g1 __asm__("g1") = (name);			\
+	long int _name = (long int) (name);				\
 	register long int __o0 __asm__ ("o0") = _arg1;			\
 	register long int __o1 __asm__ ("o1") = _arg2;			\
 	register long int __o2 __asm__ ("o2") = _arg3;			\
 	register long int __o3 __asm__ ("o3") = _arg4;			\
-	__asm __volatile (string : "=r" (__o0) :			\
-			  "r" (__g1), "0" (__o0), "r" (__o1),		\
+	__asm __volatile (string : "+r" (__o0) :			\
+			  [scn] nc (_name), "r" (__o1),			\
 			  "r" (__o2), "r" (__o3) :			\
 			  __SYSCALL_CLOBBERS);				\
 	__o0;								\
 })
+#define internal_syscall4(string,name,args...)				\
+  _internal_syscall4(string, "i", name, args)
 
-#define internal_syscall5(string,name,arg1,arg2,arg3,arg4,arg5)		\
+#define _internal_syscall5(string,nc,name,arg1,arg2,arg3,arg4,arg5)	\
 ({									\
 	long int _arg1 = (long int) (arg1);				\
 	long int _arg2 = (long int) (arg2);				\
 	long int _arg3 = (long int) (arg3);				\
 	long int _arg4 = (long int) (arg4);				\
 	long int _arg5 = (long int) (arg5);				\
-	register long int __g1 __asm__("g1") = (name);			\
+	long int _name = (long int) (name);				\
 	register long int __o0 __asm__ ("o0") = _arg1;			\
 	register long int __o1 __asm__ ("o1") = _arg2;			\
 	register long int __o2 __asm__ ("o2") = _arg3;			\
 	register long int __o3 __asm__ ("o3") = _arg4;			\
 	register long int __o4 __asm__ ("o4") = _arg5;			\
-	__asm __volatile (string : "=r" (__o0) :			\
-			  "r" (__g1), "0" (__o0), "r" (__o1),		\
+	__asm __volatile (string : "+r" (__o0) :			\
+			  [scn] nc (_name), "r" (__o1),			\
 			  "r" (__o2), "r" (__o3), "r" (__o4) :		\
 			  __SYSCALL_CLOBBERS);				\
 	__o0;								\
 })
+#define internal_syscall5(string,name,args...)				\
+  _internal_syscall5(string, "i", name, args)
 
-#define internal_syscall6(string,name,arg1,arg2,arg3,arg4,arg5,arg6)	\
+#define _internal_syscall6(string,nc,name,arg1,arg2,arg3,arg4,arg5,arg6)\
 ({									\
 	long int _arg1 = (long int) (arg1);				\
 	long int _arg2 = (long int) (arg2);				\
@@ -148,20 +160,22 @@
 	long int _arg4 = (long int) (arg4);				\
 	long int _arg5 = (long int) (arg5);				\
 	long int _arg6 = (long int) (arg6);				\
-	register long int __g1 __asm__("g1") = (name);			\
+	long int _name = (long int) (name);				\
 	register long int __o0 __asm__ ("o0") = _arg1;			\
 	register long int __o1 __asm__ ("o1") = _arg2;			\
 	register long int __o2 __asm__ ("o2") = _arg3;			\
 	register long int __o3 __asm__ ("o3") = _arg4;			\
 	register long int __o4 __asm__ ("o4") = _arg5;			\
 	register long int __o5 __asm__ ("o5") = _arg6;			\
-	__asm __volatile (string : "=r" (__o0) :			\
-			  "r" (__g1), "0" (__o0), "r" (__o1),		\
+	__asm __volatile (string : "+r" (__o0) :			\
+			  [scn] nc (_name), "r" (__o1),			\
 			  "r" (__o2), "r" (__o3), "r" (__o4),		\
 			  "r" (__o5) :					\
 			  __SYSCALL_CLOBBERS);				\
 	__o0;								\
 })
+#define internal_syscall6(string,name,args...)				\
+  _internal_syscall6(string, "i", name, args)
 
 #define INLINE_CLONE_SYSCALL(arg1,arg2,arg3,arg4,arg5)			\
 ({									\
@@ -170,15 +184,15 @@
 	long int _arg3 = (long int) (arg3);				\
 	long int _arg4 = (long int) (arg4);				\
 	long int _arg5 = (long int) (arg5);				\
+	long int _name = __NR_clone;					\
 	register long int __o0 __asm__ ("o0") = _arg1;			\
 	register long int __o1 __asm__ ("o1") = _arg2;			\
 	register long int __o2 __asm__ ("o2") = _arg3;			\
 	register long int __o3 __asm__ ("o3") = _arg4;			\
 	register long int __o4 __asm__ ("o4") = _arg5;			\
-	register long int __g1 __asm__ ("g1") = __NR_clone;		\
 	__asm __volatile (__SYSCALL_STRING :				\
 			  "=r" (__o0), "=r" (__o1) :			\
-			  "r" (__g1), "0" (__o0), "1" (__o1),		\
+			  [scn] "i" (_name), "0" (__o0), "1" (__o1),	\
 			  "r" (__o2), "r" (__o3), "r" (__o4) :		\
 			  __SYSCALL_CLOBBERS);				\
 	if (__glibc_unlikely ((unsigned long int) (__o0) > -4096UL))	\