1 files changed, 157 insertions, 116 deletions

diff --git a/arch/avr32/kernel/ptrace.c b/arch/avr32/kernel/ptrace.c
index 9e16b8a447f2..002369e44093 100644
--- a/arch/avr32/kernel/ptrace.c
+++ b/arch/avr32/kernel/ptrace.c
@@ -30,20 +30,22 @@ static struct pt_regs *get_user_regs(struct task_struct *tsk)
 
 static void ptrace_single_step(struct task_struct *tsk)
 {
-        pr_debug("ptrace_single_step: pid=%u, SR=0x%08lx\n",
-                 tsk->pid, tsk->thread.cpu_context.sr);
-        if (!(tsk->thread.cpu_context.sr & SR_D)) {
-                /*
-                 * Set a breakpoint at the current pc to force the
-                 * process into debug mode.  The syscall/exception
-                 * exit code will set a breakpoint at the return
-                 * address when this flag is set.
-                 */
-                pr_debug("ptrace_single_step: Setting TIF_BREAKPOINT\n");
-                set_tsk_thread_flag(tsk, TIF_BREAKPOINT);
-        }
+        pr_debug("ptrace_single_step: pid=%u, PC=0x%08lx, SR=0x%08lx\n",
+                 tsk->pid, task_pt_regs(tsk)->pc, task_pt_regs(tsk)->sr);
 
-        /* The monitor code will do the actual step for us */
+        /*
+         * We can't schedule in Debug mode, so when TIF_BREAKPOINT is
+         * set, the system call or exception handler will do a
+         * breakpoint to enter monitor mode before returning to
+         * userspace.
+         *
+         * The monitor code will then notice that TIF_SINGLE_STEP is
+         * set and return to userspace with single stepping enabled.
+         * The CPU will then enter monitor mode again after exactly
+         * one instruction has been executed, and the monitor code
+         * will then send a SIGTRAP to the process.
+         */
+        set_tsk_thread_flag(tsk, TIF_BREAKPOINT);
         set_tsk_thread_flag(tsk, TIF_SINGLE_STEP);
 }
 
@@ -55,23 +57,7 @@ static void ptrace_single_step(struct task_struct *tsk)
 void ptrace_disable(struct task_struct *child)
 {
         clear_tsk_thread_flag(child, TIF_SINGLE_STEP);
-}
-
-/*
- * Handle hitting a breakpoint
- */
-static void ptrace_break(struct task_struct *tsk, struct pt_regs *regs)
-{
-        siginfo_t info;
-
-        info.si_signo = SIGTRAP;
-        info.si_errno = 0;
-        info.si_code  = TRAP_BRKPT;
-        info.si_addr  = (void __user *)instruction_pointer(regs);
-
-        pr_debug("ptrace_break: Sending SIGTRAP to PID %u (pc = 0x%p)\n",
-                 tsk->pid, info.si_addr);
-        force_sig_info(SIGTRAP, &info, tsk);
+        clear_tsk_thread_flag(child, TIF_BREAKPOINT);
 }
 
 /*
@@ -84,9 +70,6 @@ static int ptrace_read_user(struct task_struct *tsk, unsigned long offset,
         unsigned long *regs;
         unsigned long value;
 
-        pr_debug("ptrace_read_user(%p, %#lx, %p)\n",
-                 tsk, offset, data);
-
         if (offset & 3 || offset >= sizeof(struct user)) {
                 printk("ptrace_read_user: invalid offset 0x%08lx\n", offset);
                 return -EIO;
@@ -98,6 +81,9 @@ static int ptrace_read_user(struct task_struct *tsk, unsigned long offset,
         if (offset < sizeof(struct pt_regs))
                 value = regs[offset / sizeof(regs[0])];
 
+        pr_debug("ptrace_read_user(%s[%u], %#lx, %p) -> %#lx\n",
+                 tsk->comm, tsk->pid, offset, data, value);
+
         return put_user(value, data);
 }
 
@@ -111,8 +97,11 @@ static int ptrace_write_user(struct task_struct *tsk, unsigned long offset,
 {
         unsigned long *regs;
 
+        pr_debug("ptrace_write_user(%s[%u], %#lx, %#lx)\n",
+                        tsk->comm, tsk->pid, offset, value);
+
         if (offset & 3 || offset >= sizeof(struct user)) {
-                printk("ptrace_write_user: invalid offset 0x%08lx\n", offset);
+                pr_debug("  invalid offset 0x%08lx\n", offset);
                 return -EIO;
         }
 
@@ -155,11 +144,9 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 {
         int ret;
 
-        pr_debug("arch_ptrace(%ld, %d, %#lx, %#lx)\n",
-                 request, child->pid, addr, data);
-
         pr_debug("ptrace: Enabling monitor mode...\n");
-        __mtdr(DBGREG_DC, __mfdr(DBGREG_DC) | DC_MM | DC_DBE);
+        ocd_write(DC, ocd_read(DC) | (1 << OCD_DC_MM_BIT)
+                        | (1 << OCD_DC_DBE_BIT));
 
         switch (request) {
         /* Read the word at location addr in the child process */
@@ -240,19 +227,16 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
                 break;
         }
 
-        pr_debug("sys_ptrace returning %d (DC = 0x%08lx)\n", ret, __mfdr(DBGREG_DC));
         return ret;
 }
 
 asmlinkage void syscall_trace(void)
 {
-        pr_debug("syscall_trace called\n");
         if (!test_thread_flag(TIF_SYSCALL_TRACE))
                 return;
         if (!(current->ptrace & PT_PTRACED))
                 return;
 
-        pr_debug("syscall_trace: notifying parent\n");
         /* The 0x80 provides a way for the tracing parent to
          * distinguish between a syscall stop and SIGTRAP delivery */
         ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
@@ -271,86 +255,143 @@ asmlinkage void syscall_trace(void)
         }
 }
 
-asmlinkage void do_debug_priv(struct pt_regs *regs)
-{
-        unsigned long dc, ds;
-        unsigned long die_val;
-
-        ds = __mfdr(DBGREG_DS);
-
-        pr_debug("do_debug_priv: pc = %08lx, ds = %08lx\n", regs->pc, ds);
-
-        if (ds & DS_SSS)
-                die_val = DIE_SSTEP;
-        else
-                die_val = DIE_BREAKPOINT;
-
-        if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP) == NOTIFY_STOP)
-                return;
-
-        if (likely(ds & DS_SSS)) {
-                extern void itlb_miss(void);
-                extern void tlb_miss_common(void);
-                struct thread_info *ti;
-
-                dc = __mfdr(DBGREG_DC);
-                dc &= ~DC_SS;
-                __mtdr(DBGREG_DC, dc);
-
-                ti = current_thread_info();
-                set_ti_thread_flag(ti, TIF_BREAKPOINT);
-
-                /* The TLB miss handlers don't check thread flags */
-                if ((regs->pc >= (unsigned long)&itlb_miss)
-                    && (regs->pc <= (unsigned long)&tlb_miss_common)) {
-                        __mtdr(DBGREG_BWA2A, sysreg_read(RAR_EX));
-                        __mtdr(DBGREG_BWC2A, 0x40000001 | (get_asid() << 1));
-                }
-
-                /*
-                 * If we're running in supervisor mode, the breakpoint
-                 * will take us where we want directly, no need to
-                 * single step.
-                 */
-                if ((regs->sr & MODE_MASK) != MODE_SUPERVISOR)
-                        set_ti_thread_flag(ti, TIF_SINGLE_STEP);
-        } else {
-                panic("Unable to handle debug trap at pc = %08lx\n",
-                      regs->pc);
-        }
-}
-
 /*
- * Handle breakpoints, single steps and other debuggy things. To keep
- * things simple initially, we run with interrupts and exceptions
- * disabled all the time.
+ * debug_trampoline() is an assembly stub which will store all user
+ * registers on the stack and execute a breakpoint instruction.
+ *
+ * If we single-step into an exception handler which runs with
+ * interrupts disabled the whole time so it doesn't have to check for
+ * pending work, its return address will be modified so that it ends
+ * up returning to debug_trampoline.
+ *
+ * If the exception handler decides to store the user context and
+ * enable interrupts after all, it will restore the original return
+ * address and status register value. Before it returns, it will
+ * notice that TIF_BREAKPOINT is set and execute a breakpoint
+ * instruction.
  */
-asmlinkage void do_debug(struct pt_regs *regs)
-{
-        unsigned long dc, ds;
+extern void debug_trampoline(void);
 
-        ds = __mfdr(DBGREG_DS);
-        pr_debug("do_debug: pc = %08lx, ds = %08lx\n", regs->pc, ds);
+asmlinkage struct pt_regs *do_debug(struct pt_regs *regs)
+{
+        struct thread_info      *ti;
+        unsigned long           trampoline_addr;
+        u32                     status;
+        u32                     ctrl;
+        int                     code;
+
+        status = ocd_read(DS);
+        ti = current_thread_info();
+        code = TRAP_BRKPT;
+
+        pr_debug("do_debug: status=0x%08x PC=0x%08lx SR=0x%08lx tif=0x%08lx\n",
+                        status, regs->pc, regs->sr, ti->flags);
+
+        if (!user_mode(regs)) {
+                unsigned long   die_val = DIE_BREAKPOINT;
+
+                if (status & (1 << OCD_DS_SSS_BIT))
+                        die_val = DIE_SSTEP;
+
+                if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP)
+                                == NOTIFY_STOP)
+                        return regs;
+
+                if ((status & (1 << OCD_DS_SWB_BIT))
+                                && test_and_clear_ti_thread_flag(
+                                        ti, TIF_BREAKPOINT)) {
+                        /*
+                         * Explicit breakpoint from trampoline or
+                         * exception/syscall/interrupt handler.
+                         *
+                         * The real saved regs are on the stack right
+                         * after the ones we saved on entry.
+                         */
+                        regs++;
+                        pr_debug("  -> TIF_BREAKPOINT done, adjusted regs:"
+                                        "PC=0x%08lx SR=0x%08lx\n",
+                                        regs->pc, regs->sr);
+                        BUG_ON(!user_mode(regs));
+
+                        if (test_thread_flag(TIF_SINGLE_STEP)) {
+                                pr_debug("Going to do single step...\n");
+                                return regs;
+                        }
+
+                        /*
+                         * No TIF_SINGLE_STEP means we're done
+                         * stepping over a syscall. Do the trap now.
+                         */
+                        code = TRAP_TRACE;
+                } else if ((status & (1 << OCD_DS_SSS_BIT))
+                                && test_ti_thread_flag(ti, TIF_SINGLE_STEP)) {
+
+                        pr_debug("Stepped into something, "
+                                        "setting TIF_BREAKPOINT...\n");
+                        set_ti_thread_flag(ti, TIF_BREAKPOINT);
+
+                        /*
+                         * We stepped into an exception, interrupt or
+                         * syscall handler. Some exception handlers
+                         * don't check for pending work, so we need to
+                         * set up a trampoline just in case.
+                         *
+                         * The exception entry code will undo the
+                         * trampoline stuff if it does a full context
+                         * save (which also means that it'll check for
+                         * pending work later.)
+                         */
+                        if ((regs->sr & MODE_MASK) == MODE_EXCEPTION) {
+                                trampoline_addr
+                                        = (unsigned long)&debug_trampoline;
+
+                                pr_debug("Setting up trampoline...\n");
+                                ti->rar_saved = sysreg_read(RAR_EX);
+                                ti->rsr_saved = sysreg_read(RSR_EX);
+                                sysreg_write(RAR_EX, trampoline_addr);
+                                sysreg_write(RSR_EX, (MODE_EXCEPTION
+                                                        | SR_EM | SR_GM));
+                                BUG_ON(ti->rsr_saved & MODE_MASK);
+                        }
+
+                        /*
+                         * If we stepped into a system call, we
+                         * shouldn't do a single step after we return
+                         * since the return address is right after the
+                         * "scall" instruction we were told to step
+                         * over.
+                         */
+                        if ((regs->sr & MODE_MASK) == MODE_SUPERVISOR) {
+                                pr_debug("Supervisor; no single step\n");
+                                clear_ti_thread_flag(ti, TIF_SINGLE_STEP);
+                        }
+
+                        ctrl = ocd_read(DC);
+                        ctrl &= ~(1 << OCD_DC_SS_BIT);
+                        ocd_write(DC, ctrl);
+
+                        return regs;
+                } else {
+                        printk(KERN_ERR "Unexpected OCD_DS value: 0x%08x\n",
+                                        status);
+                        printk(KERN_ERR "Thread flags: 0x%08lx\n", ti->flags);
+                        die("Unhandled debug trap in kernel mode",
+                                        regs, SIGTRAP);
+                }
+        } else if (status & (1 << OCD_DS_SSS_BIT)) {
+                /* Single step in user mode */
+                code = TRAP_TRACE;
 
-        if (test_thread_flag(TIF_BREAKPOINT)) {
-                pr_debug("TIF_BREAKPOINT set\n");
-                /* We're taking care of it */
-                clear_thread_flag(TIF_BREAKPOINT);
-                __mtdr(DBGREG_BWC2A, 0);
+                ctrl = ocd_read(DC);
+                ctrl &= ~(1 << OCD_DC_SS_BIT);
+                ocd_write(DC, ctrl);
         }
 
-        if (test_thread_flag(TIF_SINGLE_STEP)) {
-                pr_debug("TIF_SINGLE_STEP set, ds = 0x%08lx\n", ds);
-                if (ds & DS_SSS) {
-                        dc = __mfdr(DBGREG_DC);
-                        dc &= ~DC_SS;
-                        __mtdr(DBGREG_DC, dc);
+        pr_debug("Sending SIGTRAP: code=%d PC=0x%08lx SR=0x%08lx\n",
+                        code, regs->pc, regs->sr);
 
-                        clear_thread_flag(TIF_SINGLE_STEP);
-                        ptrace_break(current, regs);
-                }
-        } else {
-                /* regular breakpoint */
-                ptrace_break(current, regs);
-        }
+        clear_thread_flag(TIF_SINGLE_STEP);
+        _exception(SIGTRAP, regs, code, instruction_pointer(regs));
+
+        return regs;
 }