[Blackfin] arch: fix gdb testing regression

When transferring to IRQ5 from an exception, save SYSCFG in memory across the
transfer and clear the trace bit.

When we get a single step exception, check whether we can safely clear the
trace bit in SYSCFG.  We can (and should) clear it after the first instruction
of the interrupt handler; the first insn saves SYSCFG to the stack in all
handlers.

Signed-off-by: Bernd Schmidt <bernds_cb1@t-online.de>
Signed-off-by: Bryan Wu <cooloney@kernel.org>

diff --git a/arch/blackfin/mach-common/entry.S b/arch/blackfin/mach-common/entry.S
index 7365a17..038f70e 100644 (file)
--- a/arch/blackfin/mach-common/entry.S
+++ b/arch/blackfin/mach-common/entry.S
@@ -151,26 +151,62 @@ ENTRY(_ex_soft_bp)
 ENDPROC(_ex_soft_bp)
 
 ENTRY(_ex_single_step)
+       /* If we just returned from an interrupt, the single step event is
+          for the RTI instruction.  */
        r7 = retx;
        r6 = reti;
        cc = r7 == r6;
-       if cc jump _bfin_return_from_exception
-       r7 = syscfg;
-       bitclr (r7, 0);
-       syscfg = R7;
+       if cc jump _bfin_return_from_exception;
 
+       /* If we were in user mode, do the single step normally.  */
        p5.l = lo(IPEND);
        p5.h = hi(IPEND);
        r6 = [p5];
-       cc = bittst(r6, 5);
-       if !cc jump _ex_trap_c;
-       p4.l = lo(EVT5);
-       p4.h = hi(EVT5);
-       r6.h = _exception_to_level5;
-       r6.l = _exception_to_level5;
-       r7 = [p4];
-       cc = r6 == r7;
-       if !cc jump _ex_trap_c;
+       r7 = 0xffe0 (z);
+       r7 = r7 & r6;
+       cc = r7 == 0;
+       if !cc jump 1f;
+
+       /* Single stepping only a single instruction, so clear the trace
+        * bit here.  */
+       r7 = syscfg;
+       bitclr (r7, 0);
+       syscfg = R7;
+       jump _ex_trap_c;
+
+1:
+       /*
+        * We were in an interrupt handler.  By convention, all of them save
+        * SYSCFG with their first instruction, so by checking whether our
+        * RETX points at the entry point, we can determine whether to allow
+        * a single step, or whether to clear SYSCFG.
+        *
+        * First, find out the interrupt level and the event vector for it.
+        */
+       p5.l = lo(EVT0);
+       p5.h = hi(EVT0);
+       p5 += -4;
+2:
+       r7 = rot r7 by -1;
+       p5 += 4;
+       if !cc jump 2b;
+
+       /* What we actually do is test for the _second_ instruction in the
+        * IRQ handler.  That way, if there are insns following the restore
+        * of SYSCFG after leaving the handler, we will not turn off SYSCFG
+        * for them.  */
+
+       r7 = [p5];
+       r7 += 2;
+       r6 = RETX;
+       cc = R7 == R6;
+       if !cc jump _bfin_return_from_exception;
+
+       r7 = syscfg;
+       bitclr (r7, 0);
+       syscfg = R7;
+
+       /* Fall through to _bfin_return_from_exception.  */
 ENDPROC(_ex_single_step)
 
 ENTRY(_bfin_return_from_exception)
@@ -234,20 +270,26 @@ ENTRY(_ex_trap_c)
        p5.l = _saved_icplb_fault_addr;
        [p5] = r7;
 
-       p4.l = __retx;
-       p4.h = __retx;
+       p4.l = _excpt_saved_stuff;
+       p4.h = _excpt_saved_stuff;
+
        r6 = retx;
        [p4] = r6;
-       p4.l = lo(SAFE_USER_INSTRUCTION);
-       p4.h = hi(SAFE_USER_INSTRUCTION);
-       retx = p4;
+
+       r6 = SYSCFG;
+       [p4 + 4] = r6;
+       BITCLR(r6, 0);
+       SYSCFG = r6;
 
        /* Disable all interrupts, but make sure level 5 is enabled so
         * we can switch to that level.  Save the old mask.  */
        cli r6;
-       p4.l = _excpt_saved_imask;
-       p4.h = _excpt_saved_imask;
-       [p4] = r6;
+       [p4 + 8] = r6;
+
+       p4.l = lo(SAFE_USER_INSTRUCTION);
+       p4.h = hi(SAFE_USER_INSTRUCTION);
+       retx = p4;
+
        r6 = 0x3f;
        sti r6;
 
@@ -312,16 +354,17 @@ ENDPROC(_double_fault)
 ENTRY(_exception_to_level5)
        SAVE_ALL_SYS
 
-       p4.l = __retx;
-       p4.h = __retx;
+       p4.l = _excpt_saved_stuff;
+       p4.h = _excpt_saved_stuff;
        r6 = [p4];
        [sp + PT_PC] = r6;
 
+       r6 = [p4 + 4];
+       [sp + PT_SYSCFG] = r6;
+
        /* Restore interrupt mask.  We haven't pushed RETI, so this
         * doesn't enable interrupts until we return from this handler.  */
-       p4.l = _excpt_saved_imask;
-       p4.h = _excpt_saved_imask;
-       r6 = [p4];
+       r6 = [p4 + 8];
        sti r6;
 
        /* Restore the hardware error vector.  */
@@ -1349,7 +1392,14 @@ ENTRY(_sys_call_table)
        .rept NR_syscalls-(.-_sys_call_table)/4
        .long _sys_ni_syscall
        .endr
-_excpt_saved_imask:
+
+       /*
+        * Used to save the real RETX, IMASK and SYSCFG when temporarily
+        * storing safe values across the transition from exception to IRQ5.
+        */
+_excpt_saved_stuff:
+       .long 0;
+       .long 0;
        .long 0;
 
 _exception_stack:
@@ -1363,7 +1413,3 @@ _exception_stack_top:
 _last_cplb_fault_retx:
        .long 0;
 #endif
-       /* Used to save the real RETX when temporarily storing a safe
-        * return address.  */
-__retx:
-       .long 0;

diff --git a/include/asm-blackfin/entry.h b/include/asm-blackfin/entry.h
index 562c6d3..c4f721e 100644 (file)
--- a/include/asm-blackfin/entry.h
+++ b/include/asm-blackfin/entry.h
@@ -17,6 +17,11 @@
 #define        PF_DTRACE_OFF   1
 #define        PF_DTRACE_BIT   5
 
+/*
+ * NOTE!  The single-stepping code assumes that all interrupt handlers
+ * start by saving SYSCFG on the stack with their first instruction.
+ */
+
 /* This one is used for exceptions, emulation, and NMI.  It doesn't push
    RETI and doesn't do cli.  */
 #define SAVE_ALL_SYS           save_context_no_interrupts

diff --git a/include/asm-blackfin/mach-common/context.S b/include/asm-blackfin/mach-common/context.S
index fd0ebe1..c0e630e 100644 (file)
--- a/include/asm-blackfin/mach-common/context.S
+++ b/include/asm-blackfin/mach-common/context.S
@@ -28,6 +28,11 @@
  */
 
 /*
+ * NOTE!  The single-stepping code assumes that all interrupt handlers
+ * start by saving SYSCFG on the stack with their first instruction.
+ */
+
+/*
  * Code to save processor context.
  *  We even save the register which are preserved by a function call
  *      - r4, r5, r6, r7, p3, p4, p5