[SPARC64]: Move syscall success and newchild state out of thread flags.

These two bits were accesses non-atomically from assembler
code.  So, in order to eliminate any potential races resulting
from that, move these pieces of state into two bytes elsewhere
in struct thread_info.

Signed-off-by: David S. Miller <[email protected]>

Author: davem330

arch/sparc64/kernel/entry.S

@@ -1600,11 +1600,11 @@ sys_clone:	flushw
 		ba,pt		%xcc, sparc_do_fork
 		 add		%sp, PTREGS_OFF, %o2
 ret_from_syscall:
-		/* Clear SPARC_FLAG_NEWCHILD, switch_to leaves thread.flags in
-		 * %o7 for us.  Check performance counter stuff too.
+		/* Clear current_thread_info()->new_child, and
+		 * check performance counter stuff too.
 		 */
-		andn		%o7, _TIF_NEWCHILD, %l0
-		stx		%l0, [%g6 + TI_FLAGS]
+		stb		%g0, [%g6 + TI_NEW_CHILD]
+		ldx		[%g6 + TI_FLAGS], %l0
 		call		schedule_tail
 		 mov		%g7, %o0
 		andcc		%l0, _TIF_PERFCTR, %g0
@@ -1720,12 +1720,11 @@ ret_sys_call:
 	/* Check if force_successful_syscall_return()
 	 * was invoked.
 	 */
-	ldx		[%curptr + TI_FLAGS], %l0
-	andcc		%l0, _TIF_SYSCALL_SUCCESS, %g0
-	be,pt		%icc, 1f
-	 andn		%l0, _TIF_SYSCALL_SUCCESS, %l0
+	ldub		[%curptr + TI_SYS_NOERROR], %l0
+	brz,pt		%l0, 1f
+	 nop
 	ba,pt		%xcc, 80f
-	 stx		%l0, [%curptr + TI_FLAGS]
+	 stb		%g0, [%curptr + TI_SYS_NOERROR]
 
 1:
 	cmp		%o0, -ERESTART_RESTARTBLOCK

arch/sparc64/kernel/process.c

@@ -621,8 +621,8 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long sp,
 	memcpy(child_trap_frame, (((struct sparc_stackf *)regs)-1), (TRACEREG_SZ+STACKFRAME_SZ));
 
 	t->flags = (t->flags & ~((0xffUL << TI_FLAG_CWP_SHIFT) | (0xffUL << TI_FLAG_CURRENT_DS_SHIFT))) |
-		_TIF_NEWCHILD |
 		(((regs->tstate + 1) & TSTATE_CWP) << TI_FLAG_CWP_SHIFT);
+	t->new_child = 1;
 	t->ksp = ((unsigned long) child_trap_frame) - STACK_BIAS;
 	t->kregs = (struct pt_regs *)(child_trap_frame+sizeof(struct sparc_stackf));
 	t->fpsaved[0] = 0;

arch/sparc64/kernel/smp.c

@@ -137,7 +137,7 @@ void __init smp_callin(void)
 	/* Clear this or we will die instantly when we
 	 * schedule back to this idler...
 	 */
-	clear_thread_flag(TIF_NEWCHILD);
+	current_thread_info()->new_child = 0;
 
 	/* Attach to the address space of init_task. */
 	atomic_inc(&init_mm.mm_count);

arch/sparc64/kernel/traps.c

@@ -2125,6 +2125,8 @@ void __init trap_init(void)
 	    TI_PCR != offsetof(struct thread_info, pcr_reg) ||
 	    TI_CEE_STUFF != offsetof(struct thread_info, cee_stuff) ||
 	    TI_PRE_COUNT != offsetof(struct thread_info, preempt_count) ||
+	    TI_NEW_CHILD != offsetof(struct thread_info, new_child) ||
+	    TI_SYS_NOERROR != offsetof(struct thread_info, syscall_noerror) ||
 	    TI_FPREGS != offsetof(struct thread_info, fpregs) ||
 	    (TI_FPREGS & (64 - 1)))
 		thread_info_offsets_are_bolixed_dave();

include/asm-sparc64/ptrace.h

@@ -94,8 +94,9 @@ struct sparc_trapf {
 #define STACKFRAME32_SZ	sizeof(struct sparc_stackf32)
 
 #ifdef __KERNEL__
-#define force_successful_syscall_return()	\
-	set_thread_flag(TIF_SYSCALL_SUCCESS)
+#define force_successful_syscall_return()	    \
+do {	current_thread_info()->syscall_noerror = 1; \
+} while (0)
 #define user_mode(regs) (!((regs)->tstate & TSTATE_PRIV))
 #define instruction_pointer(regs) ((regs)->tpc)
 #ifdef CONFIG_SMP

include/asm-sparc64/system.h

@@ -190,24 +190,23 @@ do {	if (test_thread_flag(TIF_PERFCTR)) {				\
 	"wrpr	%%g1, %%cwp\n\t"					\
 	"ldx	[%%g6 + %3], %%o6\n\t"					\
 	"ldub	[%%g6 + %2], %%o5\n\t"					\
-	"ldx	[%%g6 + %4], %%o7\n\t"					\
+	"ldub	[%%g6 + %4], %%o7\n\t"					\
 	"mov	%%g6, %%l2\n\t"						\
 	"wrpr	%%o5, 0x0, %%wstate\n\t"				\
 	"ldx	[%%sp + 2047 + 0x70], %%i6\n\t"				\
 	"ldx	[%%sp + 2047 + 0x78], %%i7\n\t"				\
 	"wrpr	%%g0, 0x94, %%pstate\n\t"				\
 	"mov	%%l2, %%g6\n\t"						\
-	"ldx	[%%g6 + %7], %%g4\n\t"					\
+	"ldx	[%%g6 + %6], %%g4\n\t"					\
 	"wrpr	%%g0, 0x96, %%pstate\n\t"				\
-	"andcc	%%o7, %6, %%g0\n\t"					\
-	"beq,pt %%icc, 1f\n\t"						\
+	"brz,pt %%o7, 1f\n\t"						\
 	" mov	%%g7, %0\n\t"						\
 	"b,a ret_from_syscall\n\t"					\
 	"1:\n\t"							\
 	: "=&r" (last)							\
 	: "0" (next->thread_info),					\
-	  "i" (TI_WSTATE), "i" (TI_KSP), "i" (TI_FLAGS), "i" (TI_CWP),	\
-	  "i" (_TIF_NEWCHILD), "i" (TI_TASK)				\
+	  "i" (TI_WSTATE), "i" (TI_KSP), "i" (TI_NEW_CHILD),            \
+	  "i" (TI_CWP), "i" (TI_TASK)					\
 	: "cc",								\
 	        "g1", "g2", "g3",                   "g7",		\
 	              "l2", "l3", "l4", "l5", "l6", "l7",		\

include/asm-sparc64/thread_info.h

@@ -47,7 +47,9 @@ struct thread_info {
 	struct pt_regs		*kregs;
 	struct exec_domain	*exec_domain;
 	int			preempt_count;	/* 0 => preemptable, <0 => BUG */
-	int			__pad;
+	__u8			new_child;
+	__u8			syscall_noerror;
+	__u16			__pad;
 
 	unsigned long		*utraps;
 
@@ -87,6 +89,8 @@ struct thread_info {
 #define TI_KREGS	0x00000028
 #define TI_EXEC_DOMAIN	0x00000030
 #define TI_PRE_COUNT	0x00000038
+#define TI_NEW_CHILD	0x0000003c
+#define TI_SYS_NOERROR	0x0000003d
 #define TI_UTRAPS	0x00000040
 #define TI_REG_WINDOW	0x00000048
 #define TI_RWIN_SPTRS	0x000003c8	
@@ -219,10 +223,10 @@ register struct thread_info *current_thread_info_reg asm("g6");
 #define TIF_UNALIGNED		5	/* allowed to do unaligned accesses */
 #define TIF_NEWSIGNALS		6	/* wants new-style signals */
 #define TIF_32BIT		7	/* 32-bit binary */
-#define TIF_NEWCHILD		8	/* just-spawned child process */
+/* flag bit 8 is available */
 #define TIF_SECCOMP		9	/* secure computing */
 #define TIF_SYSCALL_AUDIT	10	/* syscall auditing active */
-#define TIF_SYSCALL_SUCCESS	11
+/* flag bit 11 is available */
 /* NOTE: Thread flags >= 12 should be ones we have no interest
  *       in using in assembly, else we can't use the mask as
  *       an immediate value in instructions such as andcc.
@@ -239,10 +243,8 @@ register struct thread_info *current_thread_info_reg asm("g6");
 #define _TIF_UNALIGNED		(1<<TIF_UNALIGNED)
 #define _TIF_NEWSIGNALS		(1<<TIF_NEWSIGNALS)
 #define _TIF_32BIT		(1<<TIF_32BIT)
-#define _TIF_NEWCHILD		(1<<TIF_NEWCHILD)
 #define _TIF_SECCOMP		(1<<TIF_SECCOMP)
 #define _TIF_SYSCALL_AUDIT	(1<<TIF_SYSCALL_AUDIT)
-#define _TIF_SYSCALL_SUCCESS	(1<<TIF_SYSCALL_SUCCESS)
 #define _TIF_ABI_PENDING	(1<<TIF_ABI_PENDING)
 #define _TIF_POLLING_NRFLAG	(1<<TIF_POLLING_NRFLAG)