sparc64: Rearrange thread info to cheaply clear syscall noerror state.

After fixing a couple of brainos, it even seems to work.  What's done here
is move of ->syscall_noerror right before FPDEPTH byte in ->flags and
using sth to [%g6 + TI_SYS_NOERROR] instead of stb to [%g6 + TI_FPDEPTH] in
both branches of etrap_save.  AFAICS, that ought to be solid.  Again,
deciding what to do with now unused delay slot of branch on ->syscall_noerror
and dealing with the order of tests in ret_from_sys is a separate question,
but at least that way we don't have to clean ->syscall_noerror in there at
all.  AFAICS, it ought to be a clear win - sth is not going to cost more than
stb on etrap_64.S side of things, and we are losing write on syscalls.S one.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 19 insertions, 15 deletions

diff --git a/arch/sparc/include/asm/ptrace.h b/arch/sparc/include/asm/ptrace.h
index fd9c3f21cbf0..eeed804316bf 100644
--- a/arch/sparc/include/asm/ptrace.h
+++ b/arch/sparc/include/asm/ptrace.h
@@ -202,9 +202,7 @@ struct global_reg_snapshot {
 };
 extern struct global_reg_snapshot global_reg_snapshot[NR_CPUS];
 
-#define force_successful_syscall_return()           \
-do {    current_thread_info()->syscall_noerror = 1; \
-} while (0)
+#define force_successful_syscall_return() set_thread_noerror(1)
 #define user_mode(regs) (!((regs)->tstate & TSTATE_PRIV))
 #define instruction_pointer(regs) ((regs)->tpc)
 #define instruction_pointer_set(regs, val) ((regs)->tpc = (val))
diff --git a/arch/sparc/include/asm/thread_info_64.h b/arch/sparc/include/asm/thread_info_64.h
index cfa8c38fb9c8..8511e5fcc97d 100644
--- a/arch/sparc/include/asm/thread_info_64.h
+++ b/arch/sparc/include/asm/thread_info_64.h
@@ -18,10 +18,12 @@
 #define TI_FLAG_CWP_SHIFT               40
 #define TI_FLAG_BYTE_CURRENT_DS         3
 #define TI_FLAG_CURRENT_DS_SHIFT        32
-#define TI_FLAG_BYTE_FPDEPTH            4
-#define TI_FLAG_FPDEPTH_SHIFT           24
-#define TI_FLAG_BYTE_WSAVED             5
-#define TI_FLAG_WSAVED_SHIFT            16
+#define TI_FLAG_BYTE_NOERROR            4
+#define TI_FLAG_BYTE_NOERROR_SHIFT      24
+#define TI_FLAG_BYTE_FPDEPTH            5
+#define TI_FLAG_FPDEPTH_SHIFT           16
+#define TI_FLAG_BYTE_WSAVED             6
+#define TI_FLAG_WSAVED_SHIFT            8
 
 #include <asm/page.h>
 
@@ -47,7 +49,7 @@ struct thread_info {
         struct exec_domain      *exec_domain;
         int                     preempt_count;  /* 0 => preemptable, <0 => BUG */
         __u8                    new_child;
-        __u8                    syscall_noerror;
+        __u8                    __pad;
         __u16                   cpu;
 
         unsigned long           *utraps;
@@ -77,6 +79,7 @@ struct thread_info {
 #define TI_CURRENT_DS   (TI_FLAGS + TI_FLAG_BYTE_CURRENT_DS)
 #define TI_FPDEPTH      (TI_FLAGS + TI_FLAG_BYTE_FPDEPTH)
 #define TI_WSAVED       (TI_FLAGS + TI_FLAG_BYTE_WSAVED)
+#define TI_SYS_NOERROR  (TI_FLAGS + TI_FLAG_BYTE_NOERROR)
 #define TI_FPSAVED      0x00000010
 #define TI_KSP          0x00000018
 #define TI_FAULT_ADDR   0x00000020
@@ -84,7 +87,6 @@ struct thread_info {
 #define TI_EXEC_DOMAIN  0x00000030
 #define TI_PRE_COUNT    0x00000038
 #define TI_NEW_CHILD    0x0000003c
-#define TI_SYS_NOERROR  0x0000003d
 #define TI_CPU          0x0000003e
 #define TI_UTRAPS       0x00000040
 #define TI_REG_WINDOW   0x00000048
@@ -155,6 +157,8 @@ register struct thread_info *current_thread_info_reg asm("g6");
 #define set_thread_cwp(val)             (__cur_thread_flag_byte_ptr[TI_FLAG_BYTE_CWP] = (val))
 #define get_thread_current_ds()         (__cur_thread_flag_byte_ptr[TI_FLAG_BYTE_CURRENT_DS])
 #define set_thread_current_ds(val)      (__cur_thread_flag_byte_ptr[TI_FLAG_BYTE_CURRENT_DS] = (val))
+#define get_thread_noerror()            (__cur_thread_flag_byte_ptr[TI_FLAG_BYTE_NOERROR])
+#define set_thread_noerror(val)         (__cur_thread_flag_byte_ptr[TI_FLAG_BYTE_NOERROR] = (val))
 #define get_thread_fpdepth()            (__cur_thread_flag_byte_ptr[TI_FLAG_BYTE_FPDEPTH])
 #define set_thread_fpdepth(val)         (__cur_thread_flag_byte_ptr[TI_FLAG_BYTE_FPDEPTH] = (val))
 #define get_thread_wsaved()             (__cur_thread_flag_byte_ptr[TI_FLAG_BYTE_WSAVED])
diff --git a/arch/sparc/kernel/etrap_64.S b/arch/sparc/kernel/etrap_64.S
index 786b185e6e3f..1276ca2567ba 100644
--- a/arch/sparc/kernel/etrap_64.S
+++ b/arch/sparc/kernel/etrap_64.S
@@ -92,8 +92,10 @@ etrap_save:	save	%g2, -STACK_BIAS, %sp
                 rdpr    %wstate, %g2
                 wrpr    %g0, 0, %canrestore
                 sll     %g2, 3, %g2
+
+                /* Set TI_SYS_FPDEPTH to 1 and clear TI_SYS_NOERROR.  */
                 mov     1, %l5
-                stb     %l5, [%l6 + TI_FPDEPTH]
+                sth     %l5, [%l6 + TI_SYS_NOERROR]
 
                 wrpr    %g3, 0, %otherwin
                 wrpr    %g2, 0, %wstate
@@ -152,7 +154,9 @@ etrap_save:	save	%g2, -STACK_BIAS, %sp
                 add     %l6, TI_FPSAVED + 1, %l4
                 srl     %l5, 1, %l3
                 add     %l5, 2, %l5
-                stb     %l5, [%l6 + TI_FPDEPTH]
+
+                /* Set TI_SYS_FPDEPTH to %l5 and clear TI_SYS_NOERROR.  */
+                sth     %l5, [%l6 + TI_SYS_NOERROR]
                 ba,pt   %xcc, 2b
                  stb    %g0, [%l4 + %l3]
                 nop
diff --git a/arch/sparc/kernel/syscalls.S b/arch/sparc/kernel/syscalls.S
index 1d7e274f3f2b..ed277e2fdfc8 100644
--- a/arch/sparc/kernel/syscalls.S
+++ b/arch/sparc/kernel/syscalls.S
@@ -221,8 +221,8 @@ ret_sys_call:
          * was invoked.
          */
         ldub    [%g6 + TI_SYS_NOERROR], %l2
-        brnz,a,pn %l2, 80f
-         stb    %g0, [%g6 + TI_SYS_NOERROR]
+        brnz,pn %l2, 80f
+         nop
 
         cmp     %o0, -ERESTART_RESTARTBLOCK
         bgeu,pn %xcc, 1f
diff --git a/arch/sparc/kernel/traps_64.c b/arch/sparc/kernel/traps_64.c
index fa1f1d375ffc..82af591fe43f 100644
--- a/arch/sparc/kernel/traps_64.c
+++ b/arch/sparc/kernel/traps_64.c
@@ -2547,8 +2547,6 @@ void __init trap_init(void)
                      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_RESTART_BLOCK != offsetof(struct thread_info,
                                                   restart_block) ||
                      TI_KUNA_REGS != offsetof(struct thread_info,