Merge branches 'cleanup', 'fixes', 'misc', 'omap-barrier' and 'uaccess' into for...

[linux-2.6-block.git] / arch / arm / kernel / entry-common.S

diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 92828a1dec80c1c33d051d9b76063727598495d5..30a7228eaceba758fb368f9ef16511019b1cb5c5 100644 (file)
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -24,35 +24,55 @@
 
 
        .align  5
+#if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING))
 /*
- * This is the fast syscall return path.  We do as little as
- * possible here, and this includes saving r0 back into the SVC
- * stack.
+ * This is the fast syscall return path.  We do as little as possible here,
+ * such as avoiding writing r0 to the stack.  We only use this path if we
+ * have tracing and context tracking disabled - the overheads from those
+ * features make this path too inefficient.
  */
 ret_fast_syscall:
  UNWIND(.fnstart       )
  UNWIND(.cantunwind    )
-       disable_irq                             @ disable interrupts
+       disable_irq_notrace                     @ disable interrupts
        ldr     r1, [tsk, #TI_FLAGS]            @ re-check for syscall tracing
-       tst     r1, #_TIF_SYSCALL_WORK
-       bne     __sys_trace_return
-       tst     r1, #_TIF_WORK_MASK
+       tst     r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
        bne     fast_work_pending
-       asm_trace_hardirqs_on
 
        /* perform architecture specific actions before user return */
        arch_ret_to_user r1, lr
-       ct_user_enter
 
        restore_user_regs fast = 1, offset = S_OFF
  UNWIND(.fnend         )
+ENDPROC(ret_fast_syscall)
 
-/*
- * Ok, we need to do extra processing, enter the slow path.
- */
+       /* Ok, we need to do extra processing, enter the slow path. */
 fast_work_pending:
        str     r0, [sp, #S_R0+S_OFF]!          @ returned r0
-work_pending:
+       /* fall through to work_pending */
+#else
+/*
+ * The "replacement" ret_fast_syscall for when tracing or context tracking
+ * is enabled.  As we will need to call out to some C functions, we save
+ * r0 first to avoid needing to save registers around each C function call.
+ */
+ret_fast_syscall:
+ UNWIND(.fnstart       )
+ UNWIND(.cantunwind    )
+       str     r0, [sp, #S_R0 + S_OFF]!        @ save returned r0
+       disable_irq_notrace                     @ disable interrupts
+       ldr     r1, [tsk, #TI_FLAGS]            @ re-check for syscall tracing
+       tst     r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
+       beq     no_work_pending
+ UNWIND(.fnend         )
+ENDPROC(ret_fast_syscall)
+
+       /* Slower path - fall through to work_pending */
+#endif
+
+       tst     r1, #_TIF_SYSCALL_WORK
+       bne     __sys_trace_return_nosave
+slow_work_pending:
        mov     r0, sp                          @ 'regs'
        mov     r2, why                         @ 'syscall'
        bl      do_work_pending
@@ -61,19 +81,23 @@ work_pending:
        movlt   scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
        ldmia   sp, {r0 - r6}                   @ have to reload r0 - r6
        b       local_restart                   @ ... and off we go
+ENDPROC(ret_fast_syscall)
 
 /*
  * "slow" syscall return path.  "why" tells us if this was a real syscall.
+ * IRQs may be enabled here, so always disable them.  Note that we use the
+ * "notrace" version to avoid calling into the tracing code unnecessarily.
+ * do_work_pending() will update this state if necessary.
  */
 ENTRY(ret_to_user)
 ret_slow_syscall:
-       disable_irq                             @ disable interrupts
+       disable_irq_notrace                     @ disable interrupts
 ENTRY(ret_to_user_from_irq)
        ldr     r1, [tsk, #TI_FLAGS]
        tst     r1, #_TIF_WORK_MASK
-       bne     work_pending
+       bne     slow_work_pending
 no_work_pending:
-       asm_trace_hardirqs_on
+       asm_trace_hardirqs_on save = 0
 
        /* perform architecture specific actions before user return */
        arch_ret_to_user r1, lr
@@ -173,6 +197,8 @@ ENTRY(vector_swi)
  USER( ldr     scno, [lr, #-4]         )       @ get SWI instruction
 #endif
 
+       uaccess_disable tbl
+
        adr     tbl, sys_call_table             @ load syscall table pointer
 
 #if defined(CONFIG_OABI_COMPAT)
@@ -251,6 +277,12 @@ __sys_trace_return:
        bl      syscall_trace_exit
        b       ret_slow_syscall
 
+__sys_trace_return_nosave:
+       enable_irq_notrace
+       mov     r0, sp
+       bl      syscall_trace_exit
+       b       ret_slow_syscall
+
        .align  5
 #ifdef CONFIG_ALIGNMENT_TRAP
        .type   __cr_alignment, #object