1 files changed, 165 insertions, 110 deletions

diff --git a/arch/avr32/kernel/entry-avr32b.S b/arch/avr32/kernel/entry-avr32b.S
index d7b93f12d8f7..df6c747658c1 100644
--- a/arch/avr32/kernel/entry-avr32b.S
+++ b/arch/avr32/kernel/entry-avr32b.S
@@ -264,16 +264,7 @@ syscall_exit_work:
 
 3:      bld     r1, TIF_BREAKPOINT
         brcc    syscall_exit_cont
-        mfsr    r3, SYSREG_TLBEHI
-        lddsp   r2, sp[REG_PC]
-        andl    r3, 0xff, COH
-        lsl     r3, 1
-        sbr     r3, 30
-        sbr     r3, 0
-        mtdr    OCD_BWA2A, r2
-        mtdr    OCD_BWC2A, r3
-        rjmp    syscall_exit_cont
-
+        rjmp    enter_monitor_mode
 
         /* The slow path of the TLB miss handler */
 page_table_not_present:
@@ -288,11 +279,16 @@ page_not_present:
         rjmp    ret_from_exception
 
         /* This function expects to find offending PC in SYSREG_RAR_EX */
+        .type   save_full_context_ex, @function
+        .align  2
 save_full_context_ex:
+        mfsr    r11, SYSREG_RAR_EX
+        sub     r9, pc, . - debug_trampoline
         mfsr    r8, SYSREG_RSR_EX
+        cp.w    r9, r11
+        breq    3f
         mov     r12, r8
         andh    r8, (MODE_MASK >> 16), COH
-        mfsr    r11, SYSREG_RAR_EX
         brne    2f
 
 1:      pushm   r11, r12        /* PC and SR */
@@ -303,6 +299,21 @@ save_full_context_ex:
         stdsp   sp[4], r10      /* replace saved SP */
         rjmp    1b
 
+        /*
+         * The debug handler set up a trampoline to make us
+         * automatically enter monitor mode upon return, but since
+         * we're saving the full context, we must assume that the
+         * exception handler might want to alter the return address
+         * and/or status register. So we need to restore the original
+         * context and enter monitor mode manually after the exception
+         * has been handled.
+         */
+3:      get_thread_info r8
+        ld.w    r11, r8[TI_rar_saved]
+        ld.w    r12, r8[TI_rsr_saved]
+        rjmp    1b
+        .size   save_full_context_ex, . - save_full_context_ex
+
         /* Low-level exception handlers */
 handle_critical:
         pushm   r12
@@ -439,6 +450,7 @@ do_fpe_ll:
 ret_from_exception:
         mask_interrupts
         lddsp   r4, sp[REG_SR]
+
         andh    r4, (MODE_MASK >> 16), COH
         brne    fault_resume_kernel
 
@@ -515,34 +527,76 @@ fault_exit_work:
 
 2:      bld     r1, TIF_BREAKPOINT
         brcc    fault_resume_user
-        mfsr    r3, SYSREG_TLBEHI
-        lddsp   r2, sp[REG_PC]
-        andl    r3, 0xff, COH
-        lsl     r3, 1
-        sbr     r3, 30
-        sbr     r3, 0
-        mtdr    OCD_BWA2A, r2
-        mtdr    OCD_BWC2A, r3
-        rjmp    fault_resume_user
-
-        /* If we get a debug trap from privileged context we end up here */
-handle_debug_priv:
-        /* Fix up LR and SP in regs. r1 contains the mode we came from */
-        mfsr    r2, SYSREG_SR
-        mov     r3, r2
-        bfins   r2, r1, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
-        mtsr    SYSREG_SR, r2
+        rjmp    enter_monitor_mode
+
+        .section .kprobes.text, "ax", @progbits
+        .type   handle_debug, @function
+handle_debug:
+        sub     sp, 4           /* r12_orig */
+        stmts   --sp, r0-lr
+        mfsr    r8, SYSREG_RAR_DBG
+        mfsr    r9, SYSREG_RSR_DBG
+        unmask_exceptions
+        pushm   r8-r9
+        bfextu  r9, r9, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
+        brne    debug_fixup_regs
+
+.Ldebug_fixup_cont:
+#ifdef CONFIG_TRACE_IRQFLAGS
+        rcall   trace_hardirqs_off
+#endif
+        mov     r12, sp
+        rcall   do_debug
+        mov     sp, r12
+
+        lddsp   r2, sp[REG_SR]
+        bfextu  r3, r2, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
+        brne    debug_resume_kernel
+
+        get_thread_info r0
+        ld.w    r1, r0[TI_flags]
+        mov     r2, _TIF_DBGWORK_MASK
+        tst     r1, r2
+        brne    debug_exit_work
+
+        bld     r1, TIF_SINGLE_STEP
+        brcc    1f
+        mfdr    r4, OCD_DC
+        sbr     r4, OCD_DC_SS_BIT
+        mtdr    OCD_DC, r4
+
+1:      popm    r10,r11
+        mask_exceptions
+        mtsr    SYSREG_RSR_DBG, r11
+        mtsr    SYSREG_RAR_DBG, r10
+#ifdef CONFIG_TRACE_IRQFLAGS
+        rcall   trace_hardirqs_on
+1:
+#endif
+        ldmts   sp++, r0-lr
+        sub     sp, -4
+        retd
+        .size   handle_debug, . - handle_debug
+
+        /* Mode of the trapped context is in r9 */
+        .type   debug_fixup_regs, @function
+debug_fixup_regs:
+        mfsr    r8, SYSREG_SR
+        mov     r10, r8
+        bfins   r8, r9, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
+        mtsr    SYSREG_SR, r8
         sub     pc, -2
         stdsp   sp[REG_LR], lr
-        mtsr    SYSREG_SR, r3
+        mtsr    SYSREG_SR, r10
         sub     pc, -2
-        sub     r10, sp, -FRAME_SIZE_FULL
-        stdsp   sp[REG_SP], r10
-        mov     r12, sp
-        rcall   do_debug_priv
+        sub     r8, sp, -FRAME_SIZE_FULL
+        stdsp   sp[REG_SP], r8
+        rjmp    .Ldebug_fixup_cont
+        .size   debug_fixup_regs, . - debug_fixup_regs
 
-        /* Now, put everything back */
-        ssrf    SR_EM_BIT
+        .type   debug_resume_kernel, @function
+debug_resume_kernel:
+        mask_exceptions
         popm    r10, r11
         mtsr    SYSREG_RAR_DBG, r10
         mtsr    SYSREG_RSR_DBG, r11
@@ -553,93 +607,44 @@ handle_debug_priv:
 1:
 #endif
         mfsr    r2, SYSREG_SR
-        mov     r3, r2
-        bfins   r2, r1, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
+        mov     r1, r2
+        bfins   r2, r3, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
         mtsr    SYSREG_SR, r2
         sub     pc, -2
         popm    lr
-        mtsr    SYSREG_SR, r3
+        mtsr    SYSREG_SR, r1
         sub     pc, -2
         sub     sp, -4          /* skip SP */
         popm    r0-r12
         sub     sp, -4
         retd
+        .size   debug_resume_kernel, . - debug_resume_kernel
 
+        .type   debug_exit_work, @function
+debug_exit_work:
         /*
-         * At this point, everything is masked, that is, interrupts,
-         * exceptions and debugging traps. We might get called from
-         * interrupt or exception context in some rare cases, but this
-         * will be taken care of by do_debug(), so we're not going to
-         * do a 100% correct context save here.
+         * We must return from Monitor Mode using a retd, and we must
+         * not schedule since that involves the D bit in SR getting
+         * cleared by something other than the debug hardware. This
+         * may cause undefined behaviour according to the Architecture
+         * manual.
+         *
+         * So we fix up the return address and status and return to a
+         * stub below in Exception mode. From there, we can follow the
+         * normal exception return path.
+         *
+         * The real return address and status registers are stored on
+         * the stack in the way the exception return path understands,
+         * so no need to fix anything up there.
          */
-handle_debug:
-        sub     sp, 4           /* r12_orig */
-        stmts   --sp, r0-lr
-        mfsr    r0, SYSREG_RAR_DBG
-        mfsr    r1, SYSREG_RSR_DBG
-#ifdef CONFIG_TRACE_IRQFLAGS
-        rcall   trace_hardirqs_off
-#endif
-        unmask_exceptions
-        stm     --sp, r0, r1
-        bfextu  r1, r1, SYSREG_MODE_OFFSET, SYSREG_MODE_SIZE
-        brne    handle_debug_priv
-
-        mov     r12, sp
-        rcall   do_debug
-
-        lddsp   r10, sp[REG_SR]
-        andh    r10, (MODE_MASK >> 16), COH
-        breq    debug_resume_user
-
-debug_restore_all:
-        popm    r10,r11
-        mask_exceptions
-        mtsr    SYSREG_RSR_DBG, r11
-        mtsr    SYSREG_RAR_DBG, r10
-#ifdef CONFIG_TRACE_IRQFLAGS
-        bld     r11, SYSREG_GM_OFFSET
-        brcc    1f
-        rcall   trace_hardirqs_on
-1:
-#endif
-        ldmts   sp++, r0-lr
-        sub     sp, -4
+        sub     r8, pc, . - fault_exit_work
+        mtsr    SYSREG_RAR_DBG, r8
+        mov     r9, 0
+        orh     r9, hi(SR_EM | SR_GM | MODE_EXCEPTION)
+        mtsr    SYSREG_RSR_DBG, r9
+        sub     pc, -2
         retd
-
-debug_resume_user:
-        get_thread_info r0
-        mask_interrupts
-
-        ld.w    r1, r0[TI_flags]
-        andl    r1, _TIF_DBGWORK_MASK, COH
-        breq    debug_restore_all
-
-1:      bld     r1, TIF_NEED_RESCHED
-        brcc    2f
-        unmask_interrupts
-        rcall   schedule
-        mask_interrupts
-        ld.w    r1, r0[TI_flags]
-        rjmp    1b
-
-2:      mov     r2, _TIF_SIGPENDING | _TIF_RESTORE_SIGMASK
-        tst     r1, r2
-        breq    3f
-        unmask_interrupts
-        mov     r12, sp
-        mov     r11, r0
-        rcall   do_notify_resume
-        mask_interrupts
-        ld.w    r1, r0[TI_flags]
-        rjmp    1b
-
-3:      bld     r1, TIF_SINGLE_STEP
-        brcc    debug_restore_all
-        mfdr    r2, OCD_DC
-        sbr     r2, OCD_DC_SS_BIT
-        mtdr    OCD_DC, r2
-        rjmp    debug_restore_all
+        .size   debug_exit_work, . - debug_exit_work
 
         .set    rsr_int0,       SYSREG_RSR_INT0
         .set    rsr_int1,       SYSREG_RSR_INT1
@@ -764,3 +769,53 @@ cpu_idle_enable_int_and_exit:
         IRQ_LEVEL 1
         IRQ_LEVEL 2
         IRQ_LEVEL 3
+
+        .section .kprobes.text, "ax", @progbits
+        .type   enter_monitor_mode, @function
+enter_monitor_mode:
+        /*
+         * We need to enter monitor mode to do a single step. The
+         * monitor code will alter the return address so that we
+         * return directly to the user instead of returning here.
+         */
+        breakpoint
+        rjmp    breakpoint_failed
+
+        .size   enter_monitor_mode, . - enter_monitor_mode
+
+        .type   debug_trampoline, @function
+        .global debug_trampoline
+debug_trampoline:
+        /*
+         * Save the registers on the stack so that the monitor code
+         * can find them easily.
+         */
+        sub     sp, 4           /* r12_orig */
+        stmts   --sp, r0-lr
+        get_thread_info r0
+        ld.w    r8, r0[TI_rar_saved]
+        ld.w    r9, r0[TI_rsr_saved]
+        pushm   r8-r9
+
+        /*
+         * The monitor code will alter the return address so we don't
+         * return here.
+         */
+        breakpoint
+        rjmp    breakpoint_failed
+        .size   debug_trampoline, . - debug_trampoline
+
+        .type breakpoint_failed, @function
+breakpoint_failed:
+        /*
+         * Something went wrong. Perhaps the debug hardware isn't
+         * enabled?
+         */
+        lda.w   r12, msg_breakpoint_failed
+        mov     r11, sp
+        mov     r10, 9          /* SIGKILL */
+        call    die
+1:      rjmp    1b
+
+msg_breakpoint_failed:
+        .asciz  "Failed to enter Debug Mode"